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INTRODUCTION
Ayurveda, the science of life, emphasizes the application of natural laws for the maintenance and restoration of health. Historically, medicinal flora was abundant; however, over time, many therapeutically important plant resources became scarce. Hence, an alternative was searched and medicines were prepared from metals and minerals for therapeutic benefit and metallic pharmaceutical preparations, which are comparatively stable, quick in action, rich in potency, lesser dosage and longer shelf life (Sarkar, 2000). Ayurveda has its own unique parameters for qualitative and quantitative analysis of a drug or formulations Kupipakwa rasayana is a unique pharmaceutical preparation where the drug is prepared in a glass bottle called Kachakupi, and the processing is done in a traditional furnace with a pattern of gradual temperature rise (Joshi, 2000).
Kupipakwa yogas have mineral and metallic formulations, including both Sagandha (presence of sulphur) and Nirgandha (absence of sulphur), prepared with mercury as ingredients (Harisharananandji, 2000).
Shilasindur is Sagandha, Sagni (with heating process), mercurial preparation processed by the Kupipakwa method. Shilasindur is Galastha kupipakwa rasayana (final product collected near the neck of the bottle), which is the best and fastest-acting arsenic medicine, having Mercury, Sulphur, and Realgar (AS2S2-Arsenic disulphide) as ingredients mainly used in ailments like Kustha (a group of skin disorders), Shwasa (respiratory problems including bronchial asthma), Sannipataja roga (disease caused due to involvement of 2 of the 3 bodily humours) and helps in rejuvenation (Shrilakshmi et al., 2013). Physical and chemical properties help develop quality in the final product. This is one of the essential aspects to evaluate the fixed standards of physicochemical features to ensure the desired action, due to the wide diversity of identification and manufacturing procedures. It was felt necessary to evaluate the induction of new physicochemical properties of these drugs by their unique method of preparation, which can be investigated scientifically through chemical analysis (Sarkar et al., 2008).
Sindur Kalpana is another name for Kupipakwa Rasayana Kalpana. The key ingredient in the unique Kupipakwa method is Kajjali (Shirish et al., 2013). In order to achieve the intended and advantageous effect in the finished product, temperature plays a critical role. The Kupipakwa Rasayana method involves numerous observations and safety measures. This has involved the widespread use of Mercury (Hg), also known as Parada, and the frequent use of Sulphur, also known as Gandhaka. The final product exhibits multiple chemical transformations. These days, the chemical reactivity of Parada and Gandhaka is well established (Gokarn et al., 2012).
Rasendra Chintamani, by Sri Dundukanatha (12th century A.D.), is the pioneer acharya who first introduced the preparation of Kupipakwa Rasayana. The concept of Kramagani Paka (Mrudu, Madhyama, and Tivragni), is mentioned in the text Rasendra Chintamani. The Kupipakwa Rasayana was developed in the thirteenth century by the Siddha Sampradaya. Rasa Prakash Sudhakar, authored by Acharya Yashodhara Bhat, mentions Sindura Kalpana by the name of Udaya Bhaskar Rasa, and labels Rasa Karpura by the name "Ghanasara-Rasa.". Udaya Bhaskar Rasa is prepared with the help of Sikata yantra and Kachaghati (Kupi). Under the name Sindura Rasa, Kupipakwa Rasayana is explained in the 15th, 16th, and 17th centuries. The particular process carried out with Parada and Gandhaka was carried out under controlled temperature. In summary, Gandhaka Jarana is primarily responsible for the invention of Kupipakwa Kalpana, which ultimately results in the desired outcome in the form of Balijarita Parada. During the eighth century A.D. the Gandhaka Jarana procedures was described by Govinda Bhagavatpada in his text Rasa Hridaya Tantra which is eventually developed into Kupipakwa Rasayana (Mishra, 2005).
Shilaisindur, a Kupipakwa Rasayana, is Sagandha (processed with sulphur), Sagni (processed with heat, i.e., temperature in ascending order), Galastha (found in the glass bottle neck), and Murchhita Parad Jarita (processed with mercury). It is recommended for all forms of infectious diseases, respiratory tract conditions, and skin conditions (Kumar et al., 2024).
The classical therapeutic indications of Shilasindur show meaningful correlation with its reported pharmacological activities. The formulation contains mineral components such as processed mercury (Parada), sulphur (Gandhaka), and arsenic compounds (Manashila), which after proper shodhana and Kupipakva processing are reported to exhibit antimicrobial, anti-inflammatory, immunomodulatory, and antipyretic activities (Shrilakshmi et al., 2012). These properties provide a scientific basis for its traditional use in Raktavikara, including Kuṣṭha and Visarpa, which are now understood to involve inflammatory, infective, and immune-mediated mechanisms
MATERIALS AND METHODS
Analytical research offers a set of parameters for evaluating the drug's quality and assists in the interpretation of the pharmacokinetic and pharmacodynamic properties of both the raw as well as finished pharmaceuticals (Dutta, 1996). Determining a specific chemical configuration and identifying the physico-chemical transformations and implications of various Samskara (Shodhana, Marana, etc.) are crucial goals of analytical research (Bhoyar & Khiyani, 2014).
The present study was conducted to compare the pharmaceutical preparation and analytical profile of Shilasindur (SS) prepared by two distinct classical methods — Valuka Yantra (traditional sand bath) and Electric Muffle Furnace (EMF)—in order to standardize and validate the process through both Ayurvedic and modern analytical perspectives.
Statistical analysis
Data were expressed as mean percentages. Comparative analysis was performed based on yield and physicochemical parameters.
Ethical clearance
Ethical clearance was not required as this study involved pharmaceutical standardization and in vitro analysis without the use of animal or human subjects.
Methodology
Authentication of Raw Material.
Organoleptic and Physico-chemical Parameters of the ingredients and the processing material of Shilasindur.
Physico-chemical Parameters, AAS, XRD, FTIR, ICP-AES of Shilasindur.
Microbial contamination evaluation.
Major materials
Procurement and Authentication of Raw Material
Parada, Gandhak, and Manashila, were the raw materials used in the study. They were procured according to the acceptable characters mentioned in the classics and authenticated by experts from the Department of Rasshastra and Bhaishjya kalpana of MGACH & RC, DMIHER, Wardha.
Other material required for Shodhan
Churna (Lime stone powder), Rason (Garlic-Allium sativum), Saindhava (Rock salt), Go Ghrita (Cows Ghee), Go Dugdha (Cows' Milk) and Ardrak (Ginger-Zinziber officinale) were procured from the local market.
Equipment required
Khalva yantra (mortar and pestle) was used for the purification of mercury (Hg) and arsenic disulphide (AS2S2). A stainless steel vessel, a Gas burner with a cylinder (Dhalan procedure) was used for the purification of sulphur. Valuka yantra and an Electric Muffle furnace were used for the preparation of Shilasindur (SS).
Pharmaceutical processing
All the pharmaceutical processes were carried out in the Department of Rasashastra, MGACH and RC, DMIHER, Wardha, India.
They include the following steps:
Shodhana of raw drugs.
Preparation of kajjali.
Kajjali with Manhshila.
Preparation of Shilasindur (SS). EMF Method and Valuka Yantra Method.
Shodhana of Raw Drugs
Shodhan of Parad (Mercury) (Sharma, 2000)
Churna (Safed Chuna) powder is placed in the Kharala.
Ashuddha Parada is added into this Churna.
This mixture is triturated for three days.
Then it is filtered through cotton cloth.
Nistusha Rasona was made into a paste.
Rasona Kalka was put in a Kharala and filtered Parada and Saindhav were added into it.
This mixture was triturated until Rasona Kalka attained a blackish colour.
This mixture is then washed with cold water.
Shuddha Parada was collected from this paste carefully.
Shodhan of Gandhak (Sulphur) (Madhava, 1987)
Gandhaka was coarsely powdered and placed in a stainless steel vessel containing Goghrita and subjected to Mandagni (Max 120°C) till it melted completely.
Hot Godugdha was placed in another stainless steel vessel. A piece of cotton cloth smeared with Goghrita was tied over this vessel.
When Gandhaka was completely melted, it was poured into Godugdha through the cloth.
Gandhaka was allowed to become cool in Godugdha.
After cooling, Gandhaka was taken out and washed with hot water and allowed to dry.
The same procedure was repeated thrice, and at the end of the procedure, Gandhaka was washed carefully with hot water and allowed to dry in open air at room temperature.
After drying it was preserved in air tight glass jar.
Shodhan of Manashila (Sharma, n.d.)
Ashuddha Manashila was placed in Khalvayantra and finely powdered.
Ardraka Swarasa was added to the fine powder and levigated till the mass was completely dried. This was considered as one Bhavana.
This dried mass was added with more Ardraka Swarasa, and the same process of Bhavana was repeated. At the end of this procedure, it was considered as completion of the second bhavana.
Similarly, 21 Bhavanas were offered to Manashila.
After completion of 21 Bhavanas, it was dried at room temperature and preserved in air tight glass container.
Preparation of kajjali (Sharma, 2000)
Equal parts of Shuddha Parada and Shuddha Gandhaka were taken in Khalva Yantra and triturated well for 18 hr till a fine, soft, Nischandra Kajjali was formed.
Fine powder of Shuddha Manahshila was added to the Kajjali, triturated for 12 hr, till the blend attains homogeneity to prepare Samaguna kajjali (Hg+S). They were triturated for about 30 hr till Kajjali siddha lakshanas (complete formation of Kajjali) were attained (Table 1).
| Stage of Processing | Raw Material | Quantity Before Processing (g) | Quantity After Processing / Obtained (g) | Loss / Gain (g) | Percentage Yield / Loss (%) | Duration of Processing (hr) | Remarks |
|---|---|---|---|---|---|---|---|
| Shodhana | Parada | 450 | 425 | −25 (Loss) | 94.45 (Yield) | — | Loss attributed to removal of impurities |
| Shodhana | Gandhaka | 450 | 431 | −19 (Loss) | 95.77 (Yield) | — | Loss due to melting, filtration, and handling |
| Shodhana | Manashila | 450 | 478 | +28 (Gain) | 106.22 (Yield) | — | Weight gain due to absorption of processing media |
| Kajjali Preparation | Shuddha Parada (410 g) + Shuddha Gandhaka (410 g) + Shuddha Manashila (410 g) | 1210 | 1190 | −20 (Loss) | 1.66 (Loss) | 30 | Kajjali prepared by trituration till Nishchandra and Siddha Lakshaṇas were attained |
Preparation of Shilasindur by ValukaYantra and Electric Muffle Furnace
Reference text used for preparation of Shilasindur is Rasyogsagar (Sharma, n.d.)
After drying above above-mentioned samples, Kajjali was filled in Kachakupi (glass bottle), covered with seven consecutive layers of cloth smeared with Multani mitti (fuller's earth) up to the mouth of Kachakupi and placed in Valukayantra (apparatus designed with an iron vessel filled with sand) and subjected to an Electric Muffle Furnace (Shrilakshmi & Lakshmi, 2016). After the entire apparatus was ready, wood was set to fire (ValukaYantra), following a gradual heating pattern. Hourly temperatures near the base of the glass bottle were recorded with a pyrometer. The temperature was maintained between 150oC – 250oC for mild heat, raised to 350oC – 600oC for moderate heat and intense heat up to 750oC. After the stage of fumes and flames, the bottom of the bottle appears like a rising sun that is red in colour (Udayabhaskara varna). After confirming with the copper coin test, the bottle was corked and intense heat was continued for 2 hr. Later, Kachakupi was left for self-cooling, bottle was removed from Valukayantra. The cloth with Multani mitti was scraped off, and the bottle was broken 2 inches below the collection of the SS. Later, the drug was collected by tapping over the outer surface of the glass bottle. The same procedure was repeated to prepare two other batches using the same Valuka yantra and Electric Muffle Furnace to establish pharmaceutical standardization (As shown in Figure 1).
Collection of Final Product
Three samples of each method of SS were prepared; among them, one batch was selected for further analysis on the basis of the highest yield.
Comparative Images of Shilasindur Prepared by both methods
Analytical Study
An analytical study was conducted with a view to knowing the particular chemical configuration of intermediate and final products. It includes qualitative and quantitative analysis. Qualitative data included organoleptic characters and quantitative tests for the identification of heavy metals and minerals using AAS, ICP-OES, XRD and FTIR parameters. All three samples of Shilasindur are brick red in color, smooth on the outer surface, and after powdering the final product, both samples are soft, smooth powder, tasteless and odorless.
To check solubility, 10 mL of each solvent is taken separately in a test tube. Then 100 mg of each sample of the drug is added to taken solvent. Then it is shaken for every 15 minutes up to 12 hr. After 12 hr, solubility was observed. Estimation of microbial contamination was done by the ‘Plate Count Method’. Assay of Mercury, Sulphur and Arsenic was done to estimate the quantity of respective material in intermediate and final Products (Government of India, Ministry of Health and Family Welfare, Department of AYUSH, 2007)
OBSERVATIONS AND RESULTS
Pharmaceutical study
After 7 days of triturating mercury with garlic, mercury disintegrated into tiny globules. This homogenious mixture of mercury and garlic attains blakish colour and disintegrated parad globules remains entrapped into garlic paste. On washing the blackish paste with hot water, mercury globules start mixing with each other to regain its original state. After purification of sulphur, the bright yellow crystal was changed to pleasant yellow small beads, with reduced pungent odour. After purification, the Manashila coarse powder was changed to fine, dull orange colour powder with strong, pungent ginger odour. Shiny liquid mercury was triturated with purified beads of sulphur that changed to grey coloured powder, and after triturating for 36 hr, uniform collodion-like Kajjali was prepared that attained all Samyak Siddha Kajjali Lakshanas.
Observations of Methadology
Different phases of the desired characteristics during the process were observed according to temperature pattern, namely sulphur fumes, melting and boiling of Kajjali, stage of flames and confirmatory tests like disappearance of flame, Sheeta Shalaka (cold thin iron rod) test, red hot appearance of the bottom of the bottle and copper coin test were observed and recorded in all three batches, each of SS (As showed in Figure 2). The final product was collected from the neck of Kachakupi from all the batches of SS. They were weighed and calculated for the percentage of absolute and relative yield. The batch-wise yield of Shilasindur showed variation between the two preparation methods. In SSVY batches (SSVY1–3), the percentage yield was observed as 43%, 41%, and 46.4%, respectively. In contrast, the SSEMF batches (SSEMF1–3) demonstrated comparatively higher yields of 58.4%, 65.5%, and 55.9%, respectively. These findings indicate that the EMF method yielded a greater percentage of final product than the Valuka Yantra method (Tables 2 and 3). The output of the final product in all 6 samples was around 50-60%. The highest yielded batch was subjected to various organoleptic and physicochemical parameters (Table 4).
| Sl. No. | Observation / Stage | SSEMF1 | SSEMF2 | SSEMF3 |
|---|---|---|---|---|
| 1 | Initial temperature (°C) | 30 | 29 | 30 |
| 2 | Heating started (h) | 0 | 0 | 0 |
| 3 | Initial heating acceleration | 30 | 15 | 15 |
| 4 | No visible change | 1.00 hr (110°C) | 0.35 hr (100°C) | 1.50 hr (80°C) |
| 5 | Yellow fumes (first → dense) | 4.00 hr (225°C) → 7.50 hr (255°C) | 3.05 hr (147°C) → 6.45 hr (242°C) | 3.15 hr (154°C) → 7.15 hr (240°C) |
| 6 | White fumes appearance | 5.35 hr (220°C) | 6.00 hr (200°C) | 6.25 hr (215°C) |
| 7 | Kajjali hardness / softening | Hardness not observed; softened at 13.35 hr (320°C) | Hard at 7.30 hr (250°C); softened at 8.00 hr (255°C) | Hard at 7.45 hr (250°C); softened at 8.15 hr (255°C) |
| 8 | Melting of Kajjali | Started: 9.55 hr (250°C); ++/+++ NR | Started: 11.30 hr (275°C); ++ at 13.45 hr (351°C); +++ at 15.25 hr (360°C) | Started: 11.45 hr (275°C); ++ at 14.00 hr (351°C); +++ at 15.40 hr (360°C) |
| 9 | Orange fumes (first → dense) | 11.50 hr (300°C) → 15.55 hr (355°C) | 17.15 hr (403°C) → 18.30 hr (425°C) | 17.50 hr (403°C) → 19.10 hr (425°C) |
| 10 | White flame & red bottom | 17.35 hr (400°C); 18.50 hr (450°C) | 19.15 hr (453°C); 20.45 hr (469°C) | 19.50 hr (453°C); 21.15 hr (469°C) |
| 11 | Product deposition at kupi neck | NR | 20.45 hr (469°C) | 21.15 hr (469°C) |
| 12 | Copper coin test | NR | NR | Negative at 22.15 hr (474°C) |
| 13 | Reduction of fumes & corking | 18.50 hr (450°C) | 21.30 hr (480°C) | 24.00 hr (490°C) |
| 14 | Tīvragni (start → end) | 19.05 hr (440°C) → 22.05 hr (500°C) | 22.45 hr (500°C) → 28.45 hr (548°C) | 26.00 hr (525°C) → 29.00 hr (550°C) |
| 15 | Maximum temperature (°C) | 550 | 552 | 570 |
| 16 | Heating stopped / total duration | 23.35 hr / ~23.5 hr | 31.00 hr / ~31.0 hr | 31.30 hr / ~31.5 hr |
| 17 | Final step | Kupi left for Svangasheeta | Kupi left for Svangasheeta | Kupi left for Svangasheeta |
| 18 | Kajjali taken (g) | 200 | 200 | 200 |
| 19 | Galastha yield (g) | 116.8 | 131 | 111.8 |
| 20 | Talastha yield (g) | — | — | — |
| 21 | Total yield (%) | 58.4 | 65.5 | 55.9 |
| Sl. No. | Observation / Stage | SSVY1 | SSVY2 | SSVY3 |
|---|---|---|---|---|
| 1 | Initial temperature (°C) | 30 | 30 | 33 |
| 2 | Agnisthāpana started (h) | 0 | 0 | 0 |
| 3 | Yellow fumes (first → dense) | 1.50 hr (180°C) → 9.30 hr (350°C) | 1.45 hr (170°C) → 7.45 hr (350°C) | 1.30 hr (180°C) → 12.45 hr (400°C) |
| 4 | White fumes (appearance → increase) | 6.05 hr (250°C) → 13.30 hr (445°C) | 3.50 hr (257°C) → 14.15 hr (430°C) | 6.15 hr (290°C) → 16.45 hr (455°C) |
| 5 | Kajjali melting (start → ++ → +++) | 8.00 hr (290°C) → 11.55 hr (400°C) → 18.30 hr (480°C) | 6.30 hr (320°C) → 9.35 hr (425°C) → 13.45 hr (425°C) | 9.50 hr (340°C) → 14.00 hr (420°C) → 19.30 hr (475°C) |
| 6 | Bluish flame & orange fumes | 18.30 hr (480°C) → 23.00 hr (500°C) | 10.15 hr (430°C) → 16.00 hr (450°C) | 19.30 hr (475°C) → 22.50 hr (495°C) |
| 7 | Red base / copper coin test | 21.00 hr (495°C); NR | 19.00 hr (469°C); NR | 21.50 hr (488°C); Negative at 23.30 hr (490°C) |
| 8 | Reduction of fumes & corking | After 23.30 hr (510°C) | 21.20–22.20 hr (490–492°C) | 27.50 hr (530°C) |
| 9 | Tīvrāgni (start → end) | 26.30 hr (530°C) → 31.30 hr (559°C) | 23.00 hr (500°C) → 28.00 hr (565°C) | 30.00 hr (550°C) → 32.00 hr (575°C) |
| 10 | Maximum temperature (°C) | 580 | 589 | 590 |
| 11 | Heating stopped / total duration | 35.00 hr / ~35 hr | 31.15 hr / ~31 hr | 34.00 hr / ~34 hr |
| 12 | Kajjali (200 g) → Galastha yield (%) | 86 g (43.0%) | 82 g (41.0%) | 92.8 g (46.4%) |
| Sl. No. | Parameter / Test | Shilasindur (Valuka Yantra) | Shilasindur (EMF) |
|---|---|---|---|
| 1 | Organoleptic characters: Shabda | Scratch sound on rubbing with stone | Scratch sound on rubbing with stone |
| Sparsha | Inner: slightly rough; Outer: smooth | Inner: slightly rough; Outer: smooth | |
| Rupa (Varna & Chandrika) | Reddish black; shining cut surface | Reddish brown; shining cut surface | |
| Rasa | Tasteless | Tasteless | |
| Gandha | Not specific | Not specific | |
| 2 | Physicochemical Parameters Loss on drying at 105 °C (%) | 2.73 (SSVY) | 2.30 (SSEMF) |
| Total ash (%) | 1.2 | 1.5 | |
| Acid-insoluble ash (%) | 0.05 | 0.07 | |
| Water-soluble extractive (%) | 0.8 | 0.6 | |
| Alcohol-soluble extractive (%) | 8.8 | 10.8 |
Preparation of Shilasindur (SS). EMF Method and Valuka Yantra Method.
Analytical Study
Organoleptic Characters, Physicochemical analysis and Solubility Test of Shilasindur
Results of Solubility profile
The solubility profile of the Shilasindur samples indicated that SSVY3 was soluble in chloroform, Carbon tetrachloride (CCl₄), Isopropyl Alcohol (IPA), benzene, acetone, methanol, and Methylene Dichloride (MDC). It was partially soluble in water, hydrochloric acid, petroleum ether, and ether, while remaining insoluble in glycerine. In comparison, SSMF2 exhibited a similar solubility pattern; however, it showed partial solubility in glycerine.
Estimation of Microbial contamination of Shilasindur
Microbial contamination analysis of Shilasindur samples SSVY3and SSMF2 revealed the absence of all tested microorganisms. Total viable count, Enterobacteriaceae, and total fungal count were not detected in either sample. Additionally, specific pathogenic organisms including Escherichia coli, Salmonella, Staphylococcus aureus, and Pseudomonas aeruginosa were also absent. These findings indicate that both samples comply with acceptable microbiological quality standards and are free from microbial contamination.
Results of Heavy metal analysis by ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy)
ICP-OES analysis of Shilasindur samples SS1 (EMF) and SS2 (Valuka Yantra) was carried out to evaluate their heavy metal composition and assess pharmaceutical quality. The analysis revealed mercury and arsenic as the principal constituents in both samples, which is consistent with the classical formulation of Shilasindur as a Kupipakwa Rasayana. Sample SS1 showed slightly higher levels of mercury (23.98%) and arsenic (12.95%) compared to sample SS2, which contained 20.38% mercury and 12.39% arsenic, indicating minor variations attributable to differences in the heating and processing methods (As showed in Table 5).
| Sl. No. | Element / Parameter | Unit | Analytical Method | Shilasindur (EMF) | Shilasindur (Valuka Yantra) |
|---|---|---|---|---|---|
| 1 | Lead (Pb) | % | ICP-OES | ND | ND |
| 2 | Mercury (Hg) | % | ICP-OES | 23.98 | 20.38 |
| 3 | Cadmium (Cd) | % | ICP-OES | ND | ND |
| 4 | Arsenic (As) | % | ICP-OES | 12.95 | 12.39 |
| 5 | Mercury (Hg) | % | AAS | 24.01 | 21.23 |
| 6 | Arsenic (As) | % | AAS | 13.11 | 13.33 |
| 7 | Sulphur (S) | % | AAS | 11.59 | 6.21 |
Results of Elemental Analysis by AAS (Atomic Absorption Spectroscopy)
Mercury was detected in higher concentration in SS EMF (24.01%) compared to SS VY (21.23%), indicating greater retention of mercury during EMF processing. Arsenic levels were comparable in both samples, measuring 13.11% in SS EMF and 13.33% in SS VY, suggesting uniform incorporation of arsenic-containing mineral components irrespective of the processing method. Sulphur content showed a marked difference between the two samples, with SS EMF exhibiting a higher percentage (11.59%) than SS VY (6.21%), reflecting method-dependent variations in sulphur stabilization during preparation (As showed in Table 5).
XRD Results of Shilasindur
Shilasindur (Electric Muffle Furnace) SS-1
Shilasindur (Valuka Yantra) SS-2
X-ray Diffraction (XRD) Results of Shilasindur EMF (SS-1)
Phase Identification
The XRD of Shilasindur (SS-1) exhibited sharp and well-defined diffraction peaks (As shown in Figure 3), indicating the crystalline nature of the formulation. Phase identification revealed α-mercury sulphide (HgS) as the predominant crystalline phase (≈62.5%), with characteristic intense peaks observed in the 2θ range of approximately 26–31°. Minor phases corresponding to mercury–manganese sulphide (≈15.0%) and tin arsenide (Sn₄As₃) (≈22.5%) were also detected. No diffraction peaks of free metallic mercury were observed, confirming its complete conversion into stable crystalline compounds during processing.
X-ray Diffraction (XRD) Results of Shilasindur – Valuka (SS-2)
Phase Identification
Qualitative and quantitative phase analysis, based on matching with standard reference diffraction data, revealed the presence of multiple stabilized crystalline phases. The major identified phases included α-sulphur (≈28.8%), mercury sulphide (HgS, ≈28.0%), and α-mercury sulphide (cinnabar, ≈17.7%). Additionally, tetraarsenic oxide (As₄O₆) was detected as a significant phase, contributing approximately 25.5% of the crystalline content.
The XRD of Shilasindur (SS-2) exhibited multiple sharp and intense diffraction peaks, indicating a predominantly crystalline nature of the formulation. Phase analysis revealed the presence of sulfur-based and mercury-based crystalline compounds.
The identified phases included α-sulfur as a major constituent (≈28.8%), mercury sulphide (HgS (≈28.0%), and α-mercury sulphide (cinnabar) (≈17.7%), with characteristic peaks mainly observed in the 2θ range of 26–31°. In addition, peaks corresponding to tetraarsenic oxide (As₄O₆) were detected, contributing approximately 25.5% of the crystalline content. The sharpness and high intensity of the peaks reflect good crystallinity and phase stability of the formulation. No diffraction peaks corresponding to free metallic mercury were observed, indicating its complete conversion into stable sulfide and oxide forms during the Valula yantra processing.
FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR)
Observation of Shilasindur: (Electric Muffle Furnace) SS-1 EMF
Observation of Shilasindur-(Valuka Yantra) SS-2 VY
DISCUSSION
Pharmaceutical Process
Shodhana of Parad: Purification of Parad (mercury) was done by triturating with Rason (Garlic- Zinziber officinale), Saidhav (rock salt) and churna(lime powder), which may decrease the surface tension, leading to the disintegration of mercury molecules. While triturating with churna, parad completely mixed with powder. This powder is filtered through cotton cloth to regain pure mercury. After triturating with rason and saindhav, the small globules of Parada disintegrated completely to form a uniform batter; this may be due to the binding of mercury, garlic and rock salt. This paste is converted into blackish colour. Remaining impurities of Parada may be separated during washing of this mercury garlic blackish paste with hot water. The active constituent of garlic might have reacted with the impurities, especially with mercury salts present along with mercury which help in the removal of mercury impurities, thus purifying Parada chemically (Reddy et al., 2014). After shodhan Parada obtained was brighter compared to the raw drug, which indicates the absence of physical impurities; it matches with tests described in the classics, which may indicate the absence of physical impurities like soot, etc. The loss of amount of purified mercury can occur during the process of triturating, washing and collection of purified mercury.
Shodhana of Gandhak: Gandhaka (Sulphur) purification mainly serves 3 purposes: purification, detoxification and potentiating therapeutically. During the process, when the temperature reaches 115°C, sulphur melts and dribbles down into the milk in the form of granules, leaving behind the physical impurities like mud, stones, etc., on the cloth. Since these impurities do not change at this temperature. This can be considered as purification. Sulphur is available in a combined state along with copper, lead, zinc, iron, limestone, etc., which are unwanted and retained on the cloth at 115°C. Even if these toxins pass through the cloth and fall into milk, the fat content of milk, which is in the form of microglobules, will remove the fat-soluble impurities. Melted sulphur comes in contact with milk and solidifies, preventing chances of remixing of impurities settled at the bottom. Purification of sulphur is similar to sublimation, followed by granulation. When sulphur was heated, molten sulphur passed through the cloth and condensed in the milk. Since milk has fatty acids and lipids, this helps the condensation of sulphur. Through sublimation, granulation can be achieved by melting sulphur and passing it through a small hole and cooling. The vapours of sulphur reach the bottom of the collecting flask and solidify. Sublimation always purifies the crude products (Chaudhary, 2015). Hence above purification process purifies sulphur chemically and enhances the properties of milk.
Shodhana of Manshila: During the purification of Manashila (Realgar-AS2S2), the quantity of Ardraka (Zinziber officinale) swarasa for Bhavana reduced after the 3rd Bhavana and remained constant till the 7th Bhavana. This might indicate absorption of moisture content initially and hence the quantity of ginger juice might have reduced in the consecutive Bhavana. There was a colour change in Manashila from bright reddish orange to orange, which might be due to a chemical reaction (Baragi et al., 2019). Active principle in Ardraka swarasa (Ginger- Zinziber officinale) are gingerol [(S)-5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-3-decanone] and shogaol [(E-1-(4-Hydroxy-3-methoxyphenyl) dec-4-en-3-one)]. Shogal is the reason for the pungent odour in ginger. There could be a weak interaction between As2S2 and gingerol and shogaol (Nduka, 2013). The weight increase is due to the absorption of organic molecules, Ardraka sattva/starchy portion, into the powder of As2S2.
Preparation of Kajjali: The gradual colour change of Kajjali from ash colour to complete black suggests the gradual process of amalgamation. The absence of lusture may indicate the physical absence of free mercury. When Hg is treated with S, the resultant product is HgS. This can be in two forms (alpha-red, beta-black). The black colour of Kajjali might be because of the formation of black sulphide of mercury (Joshi et al., 2021). Wet trituration helps in attaining homogeneous mixture than dry trituration. It acts as a binding agent that may help in further complex bonding of Kajjali.
Kupipakwa Kalpana Methodology: The objective of the seven layers of Mrith lepana for Kachakupi is to strengthen it for sustained heating by preventing the breaking of Kachakupi during the process. A lump of Mrith lepana was applied at the base of the bottle before wrapping, so as to avoid the air gap. Only the lower 1/3rd of the Kachakupi was filled with the drug, to provide space inside the bottle for melting, boiling and sublimation of Kajjali inside the bottle, else a large quantity may hinder the sublimation and may lead to overflow of boiling Kajjali from the mouth of Kachakupi during the process (Choudhary, 2004). Valuka yantra is specially designed for the distribution of uniform indirect heat, which may prevent temperature fluctuation of the Kachakupi. Valuka (sand) is inert, and it may render resistance to the apparatus from atmospheric temperature variations.
The temperatures recorded at the base level of the Kachakupi indicate the temperature at which the drug is being processed. Though there was an association of arsenic with Gandhaka during the stage of fumes in all samples of SS, there was a prolonged stage of fumes with a strong odour of arsenic during the process of SS, with more orange-yellow fumes deposited on Shalaka. Appearance of sulphur fumes after 2 hr of heating indicates the melting of Kajjali, which was confirmed by the Sheeta shalaka test. Appearance of dense and profuse fumes is suggestive of the melting of Kajjali and the processing of Parada with Gandhaka. Appearance of flames may indicate the burning of extra sulphur and organic matter. The haziness was observed after the stage of flames; the bottom of Kachakupi couldn't be seen clearly when viewed with torchlight. This may be due to vapours of sulphur, as the high temperature might inevitably cause the evaporation of sulphur before coming in contact with oxygen. The copper coin test may help to confirm the absence of free sulphur and the escaping of white mercury fumes. Loss in the final product compared to that of Kajjali taken may be due to the loss of major proportions of sulphur, minimum quantity of arsenic and traces of mercury (Puranik & Dhamankar, 1964). Before corking, yellowish-orange and red particles were observed in the middle portion of the bottle. This might be due to the presence of arsenic along with mercury and sulphur.
Completeness of preparation was confirmed by the following observations, like absence of flame may indicate completeness of burning organic and excess sulphur. Cessation of fumes might indicate complete escape of excess free sulphur. A copper coin turned greyish white, which was placed over the mouth of the Kachakupi; this may be due to the reaction of mercury with copper. When cold Shalaka was sent in Kachakupi without touching the sides of bottle, a yellowish orange layer was formed over the Shalaka, indicative of deposition of fumes of Shilasindur, which is due to the presence of arsenic and no remnant material adhered to the tip of the Shalaka. These tests confirm the completion of Sindura preparation and are suitable for corking of the bottle. Appearance of redness in the bottom of Kachakupi “Arunachandrodaya varna”, might suggest complete sublimation of Kajjali and the visibility of the red-hot bottle bottom. Before corking, reddish yellow shining particles were observed below the neck of bottle, which might be the initial phase of condensation of the fumes of the Shilasindur. (Dhundhukanath & Mishra, 2006)
For the collection and storage of final products, Kachakupi was removed from the sand, and then the outer multani layer was removed after self-cooling to avoid mixing of unwanted sand material in medicine. Kachakupi was broken by burning thick thread dipped in kerosene, which causes a sudden increase in temperature around the glass bottle. After the thread had burned totally, the bottle was covered with a wet cloth. Due to a sudden fluctuation in temperature, the glass bottle breaks as it cannot accommodate a sudden variation in temperature. This method of breaking helps heat the glass bottle and avoids small pieces while breaking. Shilasindur was more reddish may be due to the presence of Realgar. The change in the black colour of Kajjali to red coloured Sindura after the heat contact may be due to a change in their allotropic form and re- arrangement of crystalline structure. Orpiment and realgar vary with one sulphur atom, varying in colour from yellow to red. Similarly, the slight change in colour of Shilasindur might be due to the amount of arsenic and sulphur, exhibiting variation in colour and crystal lattice structure of final products.
ANALYTICAL STANDARDIZATION
Ayurved Prameters: Ayurveda have described subjective organoleptic parameters. The ancient parameters to evaluate Kajjali and SS were positive, suggestive of following the appropriate methods of preparation. Kajjali obtained after trituration was a black fine powder that was Slakshna (smooth), Sukshma (subtle), which could pass Rekhapurna (filled in furrows of fingers), which may denote the fineness and reduced particle size to enhance bioavailability. Nishchandratva (absence of lustre) and Tamra pareeksha (rubbing Kajjali over Copper foil) may denote the absence of free mercury in Kajjali. Varitara Kajjali (floating on water) indicates the lightness, though both mercury and sulphur are heavy enough to sink in water, but after processing, it could float on water. The final products of Shilasindur, were Kathora (hard) and solid mass (Sindura). When rubbed against paper, red colour streaks were observed, indicative of the presence of mercuric sulphide in it.
Modern Parameters
Solubility Test: Conducted in 12 media found no change in solubility by the two methods.
Microbial Load: Samples were tested for contamination of TBC-total bacterial count (CFU/g), total fungal count (CFU/g), E. coli, Salmonella, P. aeruginosa and S. aureus. The microbial profile was conducted by inoculating the sample into agar media. If there were microbes in samples, they proliferated in colonies, and each colony was counted as one microbe and so the unit was given as ‘Colonies for Unit’ (CFU). Permissible TBC and total fungal counts were 105 CFU/g and 100 CFU/g, respectively. All the samples had counts below the normal limits for bacteria and fungi. The presence of a minimum amount of microbes in samples might be due to atmospheric exposure. Absence of bacteria like E. coli, Salmonella, P. aeruginosa and S. aureus indicates that the medicine prepared will not induce any infection. This may be inferred as hygienic methods of preparation; hence, medicine is safe for consumption in regard to microbial contamination.
Physico-chemical Parameters
Ash content: 1.2%–1.5%, indicating very low inorganic non-volatile residue, typical for purified metallic compounds.
Acid Insoluble Ash: Extremely low (0.05%–0.07%), ensuring absence of sand or siliceous contaminants.
Loss on Drying (LOD): 2.3%–2.73%, suggesting minimal moisture content and excellent shelf stability.
Water and Alcohol Soluble Extractives: Revealed acceptable solubility profiles, signifying the removal of unwanted organic impurities.
These parameters collectively confirmed the processed Shilasindur's purity and stability.
Quantitative analysis: Evaluation with estimation of total mercury, is less in Shilasindur. This may be due decrease in the concentration of sulphur due to the evaporation of free sulphur and a few mercury particles while heating in open air. This mercury might have bonded with sulphur and arsenic (i.e., mercuric sulphide with arsenic). The quantity of free sulphur was comparatively SS, traces in final products denote the quantum of heat given to these products, as sulphur starts vaporising and escaping around 120°C and above, the rest of the sulphur gets bonded with mercury. Total sulphur content chronologically decreases in the final products, which may signify sulphur in bonded form after escaping of free sulphur due to the quantum of heat given to these products. The quantity of arsenic was comparatively higher in SS. This might suggest evaporation of arsenic also during this process. Odour of arsenic during the stage of fumes was more in the SS in all the trials. Quantitative analysis indicates a lower percentage of arsenic in SS. Both of them might suggest loss of more amount of arsenic in SS.
Heavy Metal Analysis by ICP-OES
In ICP-OES analysis notably, lead and cadmium were not detected in either sample of Shilasindur SSEMF and SSVY, confirming effective purification (Shodhana) of raw materials and absence of extraneous toxic contamination (Kumar et al., 2014). Overall, the ICP-OES findings demonstrate chemical consistency between both preparations, validate adherence to classical pharmaceutical procedures, and support the safety and quality of Shilasindur prepared by both EMF and Valuka Yantra methods.
Elemental Analysis by AAS
Atomic Absorption Spectroscopy (AAS) was employed to determine the elemental composition of Shilasindur samples prepared by EMF (SS EMF) and Valuka Yantra (SS VY) methods. The analysis confirmed the presence of mercury, arsenic, and sulphur as major elements in both samples, which are characteristic constituents of classical Shilasindur (Paudel et al., 2016). Overall, the AAS results demonstrate consistency with the expected elemental profile of Shilasindur and highlight minor quantitative differences attributable to pharmaceutical processing techniques rather than compositional deviation, thereby supporting the quality and authenticity of both formulations.
XRD ANALYSIS
The XRD study (as shown in Figures 4 and 5) of Shilasindur (SS-1) confirms the formation of a stable, crystalline formulation predominantly composed of α-HgS along with minor sulphide and arsenide phases. These findings validate the effectiveness of traditional Rasashastra processing methods in achieving chemical stabilization of mercury and support the pharmaceutical safety and quality of Shilasindur (Klug & Alexander, 1974).
The XRD analysis of Shilasindur SS-2 prepared by Valuka Yantra demonstrates the formation of a stable, crystalline mineral formulation comprising sulphur, mercury sulphide, and arsenic oxide phases. These findings validate the effectiveness of Valuka Yantra processing in achieving controlled mineral transformation and chemical stabilization, thereby supporting the pharmaceutical quality and toxicological safety of the Shilasindur formulation.
Fourier Transform Infrared Spectroscopy (FTIR)
The FTIR spectral profile confirms the presence of stable metal–sulphur and metal–oxygen bonds with minimal residual organic functional groups (Table 6). This indicates effective transformation of raw materials into a chemically stable form through classical pharmaceutical processing. The absence of peaks corresponding to free toxic functional groups supports the safety and stability of the formulation, validating the traditional purification and incineration procedure (Ruban et al., 2009).
| Sl. No. | Peak Region (cm⁻¹) | Shilasindur (EMF) – Interpretation | Shilasindur (Valuka Yantra) – Interpretation |
|---|---|---|---|
| 1 | 3450–3300 | Broad O–H stretching indicating hydroxyl groups / adsorbed moisture | Broad O–H stretching indicating bound moisture or hydroxyl–metal complexes |
| 2 | 2950–2850 | Weak aliphatic C–H stretching suggesting trace organic remnants from levigation media | Weak aliphatic C–H stretching indicating minimal organic residues |
| 3 | 1650–1600 | Medium H–O–H bending / C=C stretching indicating bound water or residual organic structures | Medium H–O–H bending / C=C stretching indicating structurally bound water |
| 4 | 1450–1380 | Weak–medium C–H bending / CO₃²⁻ vibration suggesting atmospheric carbonation | Weak–medium C–H bending / CO₃²⁻ vibration due to mineral matrix interaction |
| 5 | 1250–1000 | Moderate M–O and S–O stretching confirming metal–oxygen and sulphur–oxygen complexes | Strong, broad M–O, As–O and S–O stretching indicating stable inorganic/organometallic complexes |
| 6 | 900–700 | Sharp M–S / As–S stretching confirming metal–sulphur bonding | Sharp, intense M–S / As–S stretching indicating well-formed metal–sulphur bonds |
| 7 | 650–500 | Strong metal–S / metal–O lattice vibrations confirming stable inorganic lattice | Medium metal–S / metal–O lattice vibrations indicating crystalline / semi-crystalline structure |
The FTIR spectrum of sample SS-1: Demonstrates the presence of hydroxyl groups, minimal residual organic matter, and well-defined metal–oxygen and metal–sulphur bonds. The dominance of inorganic lattice vibrations in the lower wavenumber region confirms successful transformation of raw materials into a chemically stable processed form. The spectral pattern supports effective purification and processing, indicating reduced free organic content and enhanced structural stability.
The FTIR spectrum of sample SS-2: Reveals dominant metal–sulphur and metal–oxygen stretching vibrations with minimal organic functional group presence. This confirms effective transformation of raw materials into a stable inorganic form through classical pharmaceutical processing.
Thus, the analytical studies not only verified the standardization and quality of the final product but also built scientific credibility for its therapeutic use.
Pharmaceutical Findings
The entire pharmaceutical process — including Shodhana (purification) of Parada, Gandhaka, and Manahshila, followed by Kajjali preparation and Kupipakwa process — was carried out meticulously in accordance with Rasashastra guidelines.
During the Shodhana of Parada, it was observed that trituration with Sudha Churna, Rason and Saindhav effectively reduced surface tension and helped in complete disintegration of mercury globules, ensuring purification both physically and chemically.
Gandhaka Shodhana through Goghrita–Godugdha medium eliminated impurities, detoxified the raw sulphur, and potentiated its pharmaceutical properties.
Manashila Shodhana through 21 Bhavanas with Ardraka Swarasa brought about a uniform colour and texture change, indicating the conversion of the toxic arsenical compound into a therapeutically safe form.
During the Kupipakwa process, a series of classical Pariksha (tests) such as Sheeta Shalaka, Tamra Pariksha, and Arunachandrodaya Varna were successfully employed to confirm the proper transformation and completion of the product.
Among the two methods, the Electric Muffle Furnace offered a more controlled and consistent heating environment, leading to reduced manual labour, less fuel consumption, and improved reproducibility indicates the superior alternative for large scale manufacturing.
Analytical and Comparative Observations Traditional and Modern Method
The average yield of Shilasindur prepared in the Electric Muffle Furnace (≈60%) was higher than that of the Valuka Yantra method (≈43%), demonstrating superior thermal efficiency and reduced material loss.
Physicochemical parameters such as Loss on drying, Total ash, Water and Alcohol extractive values were within acceptable limits, reflecting the stability and purity of the formulations.
Heavy metal estimation confirmed by parameters like AAS, XRD, FTIR and ICP-OES demonstrates that, the presence of Mercury (Hg), Sulphur (S), and Arsenic (As) by w/w% in permissible proportions. No traces of lead or cadmium were detected, affirming the safety of the prepared formulations.
Microbial contamination studies revealed complete absence of bacterial and fungal species such as E. coli, Salmonella, Enterobacteriaceae, Staphylococcus aureus, and Pseudomonas aeruginosa, signifying that the preparations were carried out under hygienic and aseptic conditions.
Solubility analysis demonstrated partial solubility in polar and non-polar solvents, supporting the presence of stable sulphide and arsenical compounds as described in classical literature.
Interpretative Insights
The observed transformations during the process — such as change in Kajjali colour from black to red, and the development of a smooth, brick-red crystalline Sindur — indicate successful formation of mercuric sulphide-arsenic compounds with desirable physicochemical stability.
The Electric Muffle Furnace offered greater uniformity in heating and minimized Sulphur loss, ensuring better reaction kinetics and enhanced yield, while maintaining the classical properties and efficacy of Shilasindur.
Overall Inference
The study reaffirms that Shilasindur prepared by the Electric Muffle Furnace method meets the classical standards of Kupipakwa Rasayana in terms of colour, texture, yield, purity, and analytical profile.
Both methods successfully yielded pharmaceutically acceptable products; however, the EMF method is with reduced manual labour, more efficient, safer, eco-friendly, and suitable for standardization in modern Ayurvedic pharmaceutical industries.
CONCLUSION
Hence, it can be concluded that:
- Electric Muffle Furnace can be confidently adopted as a modern alternative to the traditional Valuka Yantra, ensuring consistency, precision, and reproducibility.
- The prepared both Valuka yantra and EMF samples of Shilasindur are microbiologically safe, chemically stable, and pharmaceutically potent, aligning with both Ayurvedic principles and modern scientific validation.
- Establishing such standardized analytical parameters and controlled heating techniques can serve as a benchmark for the large-scale production of Kupipakwa Rasayana, ensuring quality, safety, and therapeutic efficacy of mercurial formulations in Ayurveda.
- Clinical studies and Toxicity studies can be ruled out further to evaluate its toxicity and validation.