Formulation and In-Vitro Characterization of a Polyherbal Gel Made by the Combination of Solanum Xanthocarpum, Sarcostemma Acidum and Thuja Occidentalis Plant Extracts

Topical Drug Delivery System

Topical drug delivery systems are formulated to produce therapeutic effects directly at the site of application by facilitating drug penetration through the skin or mucosal tissues. A major benefit of this route is that it circumvents first-pass hepatic metabolism, which can significantly reduce drug bioavailability when administered orally. Moreover, topical administration eliminates the discomfort, risks, and technical challenges associated with parenteral routes and is unaffected by gastrointestinal variables such as pH fluctuations, enzymatic degradation, or gastric emptying time. Among topical dosage forms, semisolid preparations—including creams, gels, and ointments—are the most frequently employed. In addition, alternative topical systems such as foams, sprays, medicated powders, solutions, and transdermal patches are also commonly used. Topical drug delivery is particularly advantageous when other administration routes are ineffective or impractical, especially in the management of pain, contraception, and urinary incontinence.

Advantages of Topical Drug Delivery Systems

• Bypasses first-pass metabolism
• Simple, convenient, and non-invasive application
• Eliminates risks and discomfort related to intravenous administration
• Unaffected by gastrointestinal factors such as enzymes, pH, and gastric motility
• Achieves therapeutic efficacy with reduced total daily drug dose due to sustained drug release
• Minimizes fluctuations in plasma drug concentration and reduces inter- and intra-patient variability
• Allows easy discontinuation of therapy when required
• Provides a larger surface area for drug application compared to buccal or nasal routes

Disadvantages of Topical Drug Delivery Systems

• Potential for skin irritation or contact dermatitis
• Limited permeability of certain drugs across the skin barrier
• Risk of allergic or hypersensitivity reactions
• Suitable only for drugs requiring low systemic concentrations
• Possible enzymatic degradation of drugs within the epidermal layers
• Poor absorption of drugs with large particle size

Gels

Gels are semisolid dosage forms characterized by a liquid phase immobilized within a three-dimensional polymeric network formed by natural or synthetic gelling agents. The structural integrity of gels is maintained through physical or chemical cross-linking within the polymer matrix. Common natural gelling agents include tragacanth, pectin, carrageenan, agar, and alginic acid, while synthetic and semi-synthetic polymers such as methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and Carbopol polymers are widely used. Carbopols are synthetic, high-molecular-weight vinyl polymers containing ionizable carboxyl groups that contribute to gel formation and stability.

MATERIALS AND METHODS

5.1 Preliminary Investigation

5.1.1 Collection of Plant Material

The plant materials Solanum xanthocarpum, Sarcostemma acidum and Thuja occidentalis were collected from departmental herbarium for future reference.

5.1.2 Preparation of Plant Powder

Collected plant materials were shade-dried to prevent degradation of phytoconstituents. The dried samples were then coarsely pulverized using a mechanical grinder, passed through a #40 mesh sieve, and stored in airtight containers until further use.

5.2 Preparation of Extracts

Approximately 250 g of dried powdered material from Solanum xanthocarpum, Sarcostemma acidum and Thuja occidentalis was subjected to Soxhlet extraction. Initially, the powders were defatted using petroleum ether, followed by exhaustive extraction with appropriate solvents for approximately 36 hours. The extraction temperature was maintained between 40°C and 50°C. Ethanol was employed as the extraction solvent for S. xanthocarpum, whereas methanol was used for Sarcostemma acidum. The solvents were subsequently removed under reduced pressure, and the concentrated extracts were vacuum-dried using a rotary flash evaporator to obtain semisolid extracts.

(Reference: Kokate, Gokhale et al., 2005)

Plant Details-

Fig 2.1: Plant of Solanum xanthocarpum.

Solanum xanthocarpum is an important medicinal plant documented in traditional Hindu pharmacopoeia. It has long been employed for its fever-reducing and expectorant effects and is widely used in the management of respiratory disorders, including asthma, chronic cough, and catarrhal fever. The plant also forms an integral component of Dashamula, a well-known Ayurvedic polyherbal formulation consisting of ten therapeutic roots.

Fig 2.2: Plant of Sarcostemma acidum.

Sarcostemma acidum has been reported to possess a wide range of pharmacological activities. Studies indicate that the plant exhibits anti-inflammatory, analgesic, antiarthritic, spasmolytic, tocolytic, anti-asthmatic, antiallergic, and bronchospasmolytic effects. In addition, hepatoprotective and antioxidant properties have been documented. The plant has also demonstrated potential roles in the regulation of spermatogenesis, larvicidal action, immunomodulatory activity, central nervous system depressant effects, as well as antimicrobial, anti-syphilitic, and anthelmintic activities.

Fig 2.3 Plant of Thuja Occidentalis

Thuja occidentalis belonging to the family Cupressaceae. The leaves and young twigs are rich in essential oils containing thujone, flavonoids, tannins, and terpenoids, which contribute to its antimicrobial, anti-inflammatory, antiviral, antioxidant, and immunomodulatory activities. Traditionally, it is used in the management of skin disorders like warts, eczema, and fungal infections, respiratory ailments such as bronchitis and asthma, urinary tract infections, and digestive disturbances. In homeopathy, Thuja is a prominent remedy for chronic skin conditions and sycotic disorders. Despite its therapeutic potential, the plant should be used with caution, as excessive internal use may cause toxicity due to the presence of thujone, and therefore medical supervision is recommended.

2.4 Preliminary Investigation

2.4.1 Collection of Plant Material

Plant materials of Solanum xanthocarpum, Sarcostemma acidum and Thuja Occidentalis were collected from local lucknow region. The collected specimens were authenticated by, Professor and Head, Department of Botany, lucknow University, (U.P.). Voucher specimens bearing numbers IOS/Bot/SLF-028 and IOS/Bot/SLF-029, IOS/Bot/SLF-030 were deposited in the departmental herbarium for future reference.

2.4.2 Preparation of Plant Powder

The collected plant materials were thoroughly cleaned and shade-dried to preserve their phytoconstituents. After complete drying, the materials were coarsely powdered using a mechanical grinder. The powder was passed through a #40 mesh sieve to ensure uniform particle size and stored in airtight containers for further experimental use.

2.5 Extracts

Extraction Techniques

Extraction is a conventional process employed to isolate pharmacologically active compounds from crude plant materials using suitable solvents. Proper identification and authentication of plant material are essential prior to extraction. The choice of plant part and solvent depends on the nature of the desired phytoconstituents. Generally, dried and powdered plant material is preferred. The solvent used during extraction is referred to as the menstruum, while the insoluble residue remaining after extraction is known as the marc.

2.5.1 Preparation of Extracts

Different solvents were utilized to obtain phytochemical constituents from the dried plant powders. Aqueous extraction was carried out by cold maceration, whereas Soxhlet extraction was employed using ethanol, methanol, chloroform, and petroleum ether. Approximately 250 g of dried Solanum xanthocarpum fruits and Sarcostemma acidum, Thuja Occidentalis powder were subjected to Soxhlet extraction. Initially, defatting was carried out using petroleum ether, followed by exhaustive extraction with selected solvents for nearly 36 hours, maintaining the temperature between 40°C and 50°C. Ethanol was used as the extraction solvent for S. xanthocarpum, while methanol was selected for Sarcostemma acidum and Thuja Occidentalis. The solvents were removed under reduced pressure, and the concentrated extracts were vacuum-dried using a rotary flash evaporator to obtain semisolid extracts.

2.5.2 Phytochemical Screening

The prepared extracts were subjected to qualitative phytochemical analysis using standard chemical tests to identify the presence of various phytoconstituent groups.

2.5.3 Tests for Carbohydrates and Glycosides

Molisch’s Test:

The extract was treated with alcoholic α-naphthol followed by careful addition of concentrated sulfuric acid along the sides of the test tube. The appearance of a violet or brown ring at the interface indicated the presence of carbohydrates.

Legal’s Test:

To the extract, pyridine and sodium nitroprusside were added, followed by alkalinization with sodium hydroxide. Formation of a pink to red color confirmed glycosides.

Borntrager’s Test:

The extract was shaken with chloroform, and the separated organic layer was treated with dilute ammonia. A pink coloration in the ammoniacal layer indicated the presence of glycosides.

2.5.4 Tests for Alkaloids

The extract was acidified with dilute hydrochloric acid and tested with specific reagents:

• Dragendorff’s reagent: Reddish-brown precipitate
• Wagner’s reagent: Reddish-brown precipitate
• Mayer’s reagent: Cream-colored precipitate
• Hager’s reagent: Yellow precipitate

2.5.5 Tests for Proteins and Free Amino Acids

The extract was dissolved in distilled water and subjected to the following tests:

• Millon’s Test: Reddish coloration indicated proteins
• Ninhydrin Test: Violet or purple color confirmed amino acids
• Biuret Test: Violet or pink coloration signified proteins and amino acids

2,5.6 Tests for Tannins

• Ferric Chloride Test (5%): Violet coloration indicated phenolic compounds
• Lead Acetate Test (10%): Formation of a white precipitate confirmed tannins

2.5.7 Tests for Flavonoids

• Alkaline Reagent Test: Yellow coloration that disappeared upon acid addition confirmed flavonoids
• Shinoda Test: Formation of pink or magenta color indicated flavonoids

2.5.8 Tests for Fixed Oils and Fats

• Spot Test: Translucent oily spot on filter paper indicated fixed oils
• Saponification Test: Soap formation upon heating with alcoholic potassium hydroxide confirmed oils and fats

2.5.9 Tests for Steroids and Triterpenoids

Liebermann–Burchard Test:

Green coloration indicated steroids, while deep red coloration suggested triterpenoids.

Salkowski Test:

Red coloration in the lower layer confirmed steroids, whereas yellow coloration indicated triterpenoids.

Tests for Mucilage and Gums

The sample was added to absolute alcohol with continuous stirring. The precipitate obtained was dried and examined for swelling behavior, confirming mucilage and gums.

Tests for Waxes

The extract was treated with alcoholic alkali reagent. Formation of soap-like material due to saponification indicated the presence of waxes.

3. Formulation of A Suitable Topical Therapeutic System

3.1 Preparation of Hydrogel Containing Plant Extracts

Hydrogels were prepared using varying ratios of Carbopol 934 and Sodium Carboxymethyl Cellulose (CMC) (3:0, 3:1, 2:1, 1:1, 0:3, 1:2, and 1:3). The polymers were dispersed in 50 ml of distilled water with continuous stirring. Methyl and propyl parabens were dissolved separately in 5 ml of distilled water by heating, followed by cooling. Propylene glycol (5% w/v) was added and mixed with the polymer dispersion. Extracts of Solanum xanthocarpum (1 g) and Sarcostemma acidum (1 g) and Thuja Occidentalis (1 g) were dissolved in a minimal quantity of ethyl alcohol and incorporated into the gel base. The final volume was adjusted to 100 ml with distilled water. Triethanolamine was added dropwise to adjust the pH to 6.8–7.0 and achieve suitable gel consistency. Formulations F1, F2, F6, and F7 exhibited turbidity and clumping and were discarded. Clear and stable formulations (F3, F4, and F5) were selected for further evaluation. A control gel was prepared using the same procedure without plant extracts.

Preparation of Hydroalcoholic Gel Containing Plant Extracts

The optimized polymer blend was dispersed in distilled water under continuous stirring. Preservatives were dissolved separately, cooled, and mixed with propylene glycol before incorporation into the polymer base. Plant extracts were dissolved in ethanol and added to the formulation. The final volume was adjusted to 100 ml with distilled water, and triethanolamine was added to adjust the pH between 6.8 and 7.0. A control hydroalcoholic gel was prepared similarly without plant extracts.

Characterization and Evaluation of The Formulation

4.1 Preliminary Phytochemical Screening

Preliminary phytochemical investigations were carried out on various solvent extracts of Solanum xanthocarpum and Sarcostemma acidum, Thuja Occidentalis to identify the presence of major bioactive constituents. Standard qualitative chemical tests were performed, and the observations are summarized in Tables 6.1(a) and 6.2(b). The results indicate variation in phytoconstituent distribution depending on the solvent used.

4.2 Extractive Values

The extractive values of different solvent extracts of both plants were determined to evaluate the solubility of phytoconstituents in various solvents. The percentage yield of extracts is presented in Tables 6.3(a) and 6.3(b)

4.3 (a): Extractive values of Solanum xanthocarpum

Table 4.3(b): Extractive values of Sarcostemma acidum

The findings revealed that Solanum xanthocarpum exhibited higher extractive value in ethanol, whereas Sarcostemma acidum showed maximum extractive yield in methanol. Since the major active constituents were predominantly present in these extracts, the ethanolic extract of S. xanthocarpum and methanolic extract of S. acidum were selected for further formulation and evaluation studies.

4.3 Evaluation of Gel Formulation

4.3.1 Physical Examination

All prepared gel formulations were visually inspected for organoleptic characteristics such as color, texture, homogeneity, and overall appearance. The formulations exhibited a uniform greenish color and smooth consistency without any visible particulate matter.

4.3.2 pH Measurement

The pH of the formulated gels was determined using a calibrated digital pH meter. One gram of gel was dispersed in 100 mL of distilled water and allowed to equilibrate for two hours. Measurements were performed in triplicate, and the average pH values were recorded to ensure accuracy and reproducibility.

4.4 Composition of Gel Formulations

Different gel formulations (F1–F7 and FH)

Table 4.4: Composition of gel formulations containing plant extracts=