Formulation and Evaluation of a Polyherbal Gel Containing Solanum Xanthocarpum and Sarcostemma Acidum Plant Extracts

Topical Drug Delivery System

Topical drug formulations are designed to exert localized effects at the site of application by allowing the drug to penetrate the skin or mucous membrane layers¹. One of the key advantages of this delivery route is the bypassing of first-pass metabolism, which can otherwise reduce drug effectiveness². Additionally, topical preparations avoid the complications and discomforts associated with intravenous therapy and are not affected by gastrointestinal factors such as pH variation, enzymatic activity, or gastric emptying time³. Among the various types of topical formulations, semisolids—such as creams, gels, and ointments—are most commonly used. However, other forms like foams, sprays, medicated powders, solutions, and medicated adhesive patches are also widely utilized. Topical systems are often employed when other routes of drug delivery are ineffective or unsuitable, particularly in areas such as pain relief, birth control, and treatment of urinary incontinence.

 Advantages of Topical Drug Delivery Systems:

• Avoidance of first-pass metabolism.
• Convenient and easy to apply.
• Avoid the risks and inconveniences of intravenous therapy and the varied conditions of absorption, such as pH changes, the presence of enzymes, gastric emptying time, etc⁵.
• Achievement of efficacy with a lower total daily dosage of the drug by continuous drug input.
• Avoids fluctuation in drug levels, as well as inter- and intrapatient variations.
• Ability to easily terminate the medications when needed.
• A relatively large area of application in comparison with the buccal or nasal cavity

Disadvantages of Topical Drug Delivery Systems:

• Skin irritation of contact dermatitis
• Poor permeability of some medications through the Skin.
• Possibility of allergenic reactions.
• Can be used only for drugs that require minimal plasma concentration for action
• Enzymes in the epidermis may denature the drugs
• Drugs of larger particle size are not easy to absorb through the Skin

Gels

Gels are semi-solid systems in which a liquid phase is dispersed within a three- dimensional polymer network, formed from natural or synthetic gums. These systems rely on a high degree of physical or chemical cross-linking to maintain their structure. Polymers commonly used in gel formulations include natural gums such as tragacanth, pectin, carrageenan, agar, and alginic acid, as well as synthetic and semi-synthetic agents like methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and Carbopols—a class of synthetic vinyl polymers containing ionizable carboxyl groups⁶.

MATERIAL & METHODS

5.1 Prliminary Investigation   

2.1 Collection of Plant Material

Solanum xanthocarpum and Sarcostemma acidum specimens were gathered from the Bhopal region. Dr. S. N. Verma, professor and head of the Department of Botany at SAGE University, Indore, Madhya Pradesh, confirmed the authenticity of the collected plants. A voucher specimen (No. IOS/Bot/SLF-033 and IOS/Bot/SLF-034) has been duly archived in the department for future reference.

2.1.2 Preparation of Plant Powder

After collection, the plant materials were shade-dried to preserve their phytochemical constituents. Once dried, they were coarsely powdered using a mechanical grinder. The powdered material was then passed through a #40 mesh sieve and stored in airtight containers for subsequent experimental procedures⁷.

2.2 Preparation of Extracts

Approximately 250 g each of Solanum xanthocarpum and Sarcostemma acidum (dried powder) were subjected to Soxhlet extraction. Initially, defatting was performed using petroleum ether, followed by exhaustive extraction using the selected solvents for about 36 hours. The process temperature was maintained between 40°C and 50°C. Ethanol was chosen as the solvent for S. xanthocarpum, while methanol was used for Sarcostemma acidum. After extraction, the solvents were evaporated under reduced pressure. The concentrated extracts were then vacuum dried using a rotary flash evaporator to obtain a semisolid mass. (Reference: Kokate, Gokhale et al., 2005)

Plant Details-

Fig 2.1: Plant of Solanum xanthocarpum.

Solanum xanthocarpum holds a prominent place in Hindu Materia Medica and is traditionally used for its expectorant and antipyretic properties. It is especially valued for treating respiratory conditions such as asthma, persistent cough, and catarrhal fever. Notably, it is one of the key constituents in Dashamula, a renowned Ayurvedic formulation comprising ten medicinal roots

Fig 2.2: Plant of Sarcostemma acidum.

Sarcostemma acidum has been documented to exhibit a broad spectrum of pharmacological effects. These include anti-inflammatory, analgesic, antiarthritic, spasmolytic, tocolytic, anti-asthmatic, antiallergic, bronchospasmolytic, hepatoprotective, and antioxidant activities. Additionally, the plant has shown potential in spermatogenesis regulation, larvicidal activity, immunomodulation, CNS depression, antimicrobial, anti-syphilitic, and anthelmintic properties.

2.3 Phytochemical Screening

The extracts obtained were analyzed for the presence of different classes of phytochemicals through standard qualitative tests.

2.3.1 Tests for Carbohydrates and Glycosides

Molisch’s Test:

A few drops of 1% alcoholic α-naphthol solution were added to the sample, followed by gentle addition of concentrated sulfuric acid along the side of the test tube. Formation of a violet or brown ring at the junction indicates the presence of carbohydrates.

Borntrager’s Test:

The extract was mixed with chloroform, and the chloroform layer was separated. An equal amount of dilute ammonia was added. Development of a pink hue in the ammoniacal layer indicates glycosides⁹.

2.3.2 Test for Alkaloids

A small quantity of the extract was treated with dilute hydrochloric acid and then subjected to various reagents (e.g., Mayer's, Dragendorff’s, Wagner’s) to detect the presence of alkaloids.

The reagents are: -

• • Dragendroff's reagent -   Reddish brown ppt
  • Wagner's reagent     -   Reddish brown ppt            
  • Mayer's reagent       -   Cream colour ppt
  • Hager's reagent        -   Yellow colour ppt

2.3.3 Test for Proteins and Free Amino Acids

• • A small portion of the extract was dissolved in a few milliliters of distilled water and subjected to the following standard tests:
  • Ninhydrin Test: Development of a purple or violet hue confirms the presence of amino acids and proteins.
  • Biuret Test: Equal volumes of 5% sodium hydroxide and 1% copper sulfate solutions were mixed with the extract. The appearance of a violet or pinkish color signifies the presence of proteins and amino acids²⁰

  2.3.4 Test for Tannins

• • To detect tannins and phenolic compounds, a small amount of the sample was mixed with water and treated with the following reagents:
  • Dilute Ferric Chloride (5%) – A violet coloration confirms the presence of phenolic compounds or tannins.

  2.3.5 Test for Flavonoids

• • Alkaline Reagent Test: Upon adding a few drops of magnesium hydroxide solution to the extract, an intense yellow coloration develops. This yellow color turns colorless when a few drops of dilute acid are added, suggesting the presence of flavonoids.
  • Shinoda Test: A small quantity of the extract was dissolved in ethanol. Magnesium turnings were added, followed by the dropwise addition of concentrated hydrochloric acid and gentle heating. The appearance of a magenta or pink color indicates the presence of flavonoids²¹.

2.3.6 Tests for Fixed Oils and Fats

• • Spot Test: A small quantity of the extract was pressed between two pieces of filter paper. The presence of an oily translucent stain on the paper signifies the presence of fixed oils.
  • Saponification Test: To another portion of the sample, a few drops of 0.5 N alcoholic potassium hydroxide and one drop of phenolphthalein were added. The mixture was heated in a water bath for 1–2 hours. The appearance of soap or partial neutralization of the alkali confirms the presence of fixed oils and fats.

 2.3.7 Tests for Steroids and Triterpenoids

Libermann-Burchard Test:

A few drops of acetic anhydride were added to the sample, followed by gentle heating and subsequent cooling. Then, concentrated sulfuric acid was carefully introduced along the sides of the test tube. The presence of a brown ring at the interface of the layers and a greenish tint in the upper layer indicates steroids. A deep red coloration signifies the presence of triterpenoids²¹.

2.3.8 Test for Mucilages and Gums

A small amount of the sample was slowly introduced into 25 ml of absolute alcohol under constant stirring. The mixture was then filtered, and the precipitate was dried in oil. The dried mass was observed for swelling behavior, which helps confirm the presence of mucilage and gum.

2.3.9 Test for Waxes

To the test solution, an alcoholic alkali reagent was added. The formation of soap-like substances due to saponification indicates the presence of waxes³⁴.

2.4 Formulation of A Suitable Topical Therapeutic System

2.4.1 Preparation of Hydrogel Containing Plant Extracts:

For hydrogel preparation, different ratios of Carbopol 934 and Sodium Carboxymethyl Cellulose (CMC)—including 3:0, 3:1, 2:1, 1:1, 0:3, 1:2, and 1:3—were dispersed in 50 ml of distilled water with constant stirring. Separately, 5 ml of distilled water was used to dissolve the necessary quantities of methyl and propyl parabens by heating on a water bath. After cooling, 5% w/v of propylene glycol was added to this solution and mixed with the polymer dispersion. Plant extracts of Solanum xanthocarpum (1 g) and Sarcostemma acidum (1 g) were dissolved in a minimal quantity of ethyl alcohol and then incorporated into the polymer solution. The total volume was adjusted to 100 ml with distilled water. All components were thoroughly blended to form a uniform gel base. To achieve the desired pH (between 6.8 and 7) and optimal consistency, triethanolamine was added gradually. Some batches (F1, F2, F6,) showed turbidity and clumping and were therefore discarded. Only stable and clear batches (F3, F4, F5 and FH) were selected for further evaluation. A control gel was prepared following the same procedure but without incorporating any plant extract³⁷.

RESULT -

 3.0 Characterization and Evaluation of Formulation

Table 3.1 (a): Preliminary phytochemical screening of different extract of Solanum xanthocarpum

(+ Present, - Absent)

Table 3.2(b): Preliminary phytochemical screening of different extract of S. acidum.

 (+ Present, - Absent)

Table 3.3(a): Extractive values of Solanum xanthocarpum.

Table 3.4(b): Extractive values of Sarcostemma acidumr

Since the major active constituents are present in extract of Solanum xanthocarpum and extract of S. acidum,

4. Evaluation of Gel Formulation

4.1 Physical Assessment

Each gel formulation was examined visually for its organoleptic properties, including color, consistency, and overall appearance.

4.2 pH Determination

The pH of each formulation was assessed using a calibrated digital pH meter. For this, one gram of gel was mixed with 100 mL of distilled water and allowed to stand for two hours to equilibrate. Measurements were taken three times for each sample, and the mean value was recorded for accuracy.

Table 6.4: Formulations of Gel containing Plants extract.

Each formulation contains distilled water up to 100 ml.

FE = Ethosome gel containing S. xanthocarpum and S. acidum plant extract

F_1, to F₇ = Hydrogel, FH = Hydroalcohalic gel

5. Formulation Characterization and Evaluation of Topical Therapeutic System      

5.1 Evaluation of Gel Formulation

During the formulation trials, varying concentrations of Carbopol and Sodium CMC were tested. As the concentrations were increased or decreased, issues related to uniformity, spreadability, and viscosity emerged in certain batches (F1, F2, F5, and FH) containing both plant extracts. Due to these inconsistencies, those specific batches were excluded from further analysis. The remaining batches (F3, F4, and F6) demonstrated acceptable physical and performance characteristics and were selected for continued evaluation⁴¹. Among them, batch FH exhibited favorable results, showing a greenish, semi-transparent appearance with smooth texture and no lumps. It also had optimal spreadability, consistent viscosity, appropriate pH, and satisfactory drug content. Furthermore, the formulation remained stable in terms of appearance, spreadability, pH, and active content during accelerated stability testing. Based on these results, a hydroalcoholic gel was prepared using the FH formulation, which also showed promising physicochemical properties.

Table 5.2: Physical evaluation of all formulation

Compatibility studies:

FTIR Spectral Analysis and Standard Calibration Curve

The Fourier Transform Infrared (FTIR) spectroscopy method was employed to assess any potential physical or chemical interactions between the plant extracts and the excipients used in the gel formulation. As illustrated in Figures, no significant shifts or disappearance of characteristic peaks were observed in the IR spectra of the extract-polymer combinations. This suggests that there were no notable interactions between the active compounds and the excipients. The spectral peaks of the formulation matched those of the individual plant extracts, confirming their compatibility within the formulation.

Standard Calibration Curve of Solanum xanthocarpum Extract

A standard calibration curve for the Solanum xanthocarpum extract was established by measuring absorbance at 206 nm across different concentrations, in accordance with Beer’s Law. The results of this calibration are presented in Table

5.4: Standard calibration curve of S. xanthocarpum at 206 nm

Table 5.5: Standard calibration curve of S. xanthocarpum at 206 nm

Figure 5.7: Standard calibration curve of S. xanthocarpum at 206 nm.

Table 5: Standard calibration curve of S. xanthocarpum at 206 nm.

Standard calibration curve of S. acidum plant extract for its active constituent

Standard calibraction curve of S. acidum extract was determined by plotting absorbace vs concentraction at 359 nm and it follow the beer’s law. The results are shown in Table.

Table Percentage Drug release of Formulated Hydroalcohalic Gel at 206 nm.

Figure: Release profile of Hydrogel F-6 and Hydroalcohalic gel FH

Figure First order kinetics of formulation FH through fabricated diffusion cell.

Figure 6.: Higuchi model of formulation FH through fabricated diffusion cell

6.15 Stability Study

The formulated gels were subjected to stability studies. No colour fading was observed for all prepared gels. The pH of all formulations remained unchanged and was within the range of 6.2-7.2. The viscosity and spreadability of all gels remained unaltered and were found to be within the range. The drug content was within the 90% -103% limit for all gel formulations.

Table: Accelerated Stability study of formulated gel