Carbopol-Based Polyherbal Hydrogel Formulation with Potent Antioxidant Properties from Clitoria ternatea and Persea americana

The growing interest in safe and effective topical therapies has accelerated research in phytopharmaceuticals. Among the promising botanical candidates are Daucus carota (carrot), Persea americana (avocado), and Clitoria ternatea (butterfly pea), known for their traditional medicinal properties including hydration, anti-aging, photoprotection, and anti-inflammatory effects^[1]. However, their potential remains underutilized in modern hydrogel-based pharmaceutical formulations. Hydrogels are semi-solid systems characterized by a dilute, cross-linked polymer network that retains a large amount of water and exhibits solid-like behavior. Owing to their biocompatibility, structural integrity, and ability to incorporate bioactive compounds, hydrogels serve as an effective platform for topical drug delivery^[2]. The selection of Clitoria ternatea, Persea americana, and Daucus carota in this study was based on their established pharmacological profiles. C. ternatea is rich in anthocyanins with potent antioxidant activity. P. americana seeds contain catechins, a class of flavonoids with antioxidant and potential skin-lightening effects, which may be validated via in vitro assays following in silico molecular docking studies. Avocado peels, a cost-effective source, exhibit higher phenolic content and antioxidant capacity compared to the pulp, containing catechins, procyanidins, quercetins, and chlorogenic acid derivatives. The avocado fruit is also abundant in lipid-soluble antioxidants such as carotenoids, tocopherols, and phytosterols, along with monounsaturated oleic acid^[3][4].

1.1 What is Hydrogel?

A suitable hydrophilic gelling agent is used to gel an aqueous dispersion medium to form a hydrogel. Hydrogels are three-dimensional networks of hydrophilic polymers capable of absorbing significant amounts of water. These structures can be stabilized through either physical or chemical crosslinking, which provides their network formation and mechanical integrity. Hydrogels with physical crosslinks are known as "reversible" or "physical" hydrogels, while chemically crosslinked hydrogels, also called "permanent" hydrogels, consist of covalently bonded networks ^[7][8]. Drug release from hydrogels can occur through two main mechanisms: diffusion and chemical stimulation. With recent advancements in hydrogel technology, their applications in biomedical fields have expanded significantly, including areas such as controlled drug delivery, tissue engineering, and cell encapsulation. In response to growing demands in medicine and pharmaceuticals, numerous innovative hydrogel-based delivery systems have been developed ^[2]. Due to their ability to absorb up to 90% water, hydrogels are considered superabsorbent materials. This high water content makes them more similar to natural living tissues than most other biologically based materials. Their water-retention properties also make them valuable for studying the behavior of swollen polymer networks and for a wide range of applications, including contact lenses, protein drug delivery systems, and more^[9].

1.2 Plant Profile

1. Clitorea ternatea

Synonym: Blue butterfly pea flower. Gokarna

Family: Fabaceae

Source: Air dried flowering tops of Clitorea ternatea

Uses: Anti-aging, anti-inflammatory, anti-microbial, analgesic.cye ailments,anti-diabetic,etc.

Chemical constituents: The plant's many phenolic chemicals, particularly those found in the flower petals, are what provide the plant its positive benefits. Numerous bioactive substances, including ternatin anthocyanins, alkaloids, tannins, glycosides, resins, steroids, saponins. flavonoids, and phenols, are found in C. ternatea. These chemicals are isolated in a hydrophilic extract and include kaempferol, rutin, quercetin, and myricetin^[6][10].

2. Persea americana

Synonym: Avocado, alligator pear,butterfruit

Family: Lauraceae

Source: Ripe fruits of plant Persea americana

Uses: Anti-hyperpigmentation, skin lightning,anti-inflammatory, wound healing activity. analgesic

Chemical constituents:

1.Seed- Avocado seeds (Persea americana Mill.) are rich in compounds with strong antioxidant action called flavonoids, or catechins. Generally speaking, flavonoids are substances that have skin-lightening properties. Activity of cat chin as a skin-whitening agent^[7].

2.Peel- Flavonoids (including catechins, procyanidins, and quercetins) and derivatives of chlorogenic acid (such caffeoylquinic acids and coparoylquinic acids) make up the majority of the phenolics found in avocado peels.

3. Pulp oil: Tocopherol (vitamin E), oleic acid, palmitic acid, etc^[11][12].

1.3 Rationale of study

Hydrogels represent a type of combination product that enhances drug delivery by integrating both gel and emulsion components. This formulation merges the benefits of each system, enabling more efficient delivery of active ingredients. The primary goal of this experimental study is to create an effective, herbal, non-comedogenic skincare solution that simplifies the routine by combining three steps into one, thereby saving time and improving ease of use. The objective is to develop a single, multi-functional product that addresses essential skincare needs, offering a natural, sulphate-free, and paraben-free alternative to multiple conventional products. Hydrogels can be formulated using either oil-in-water or water-in-oil emulsions—where oil-in-water is ideal for delivering lipophilic drugs and water-in-oil for hydrophobic drugs. This formulation is thixotropic, non-greasy, spreads easily, washes off effortlessly, is emollient and non-staining, biocompatible, transparent, and cosmetically appealing. It also boasts excellent skin penetration and a long shelf life. While gels and emulsions each offer unique advantages, traditional gels may be limited in delivering hydrophobic compounds. Hydrogels overcome this drawback by incorporating a gelling agent to transform emulsions into a more versatile and stable form. Modern consumers increasingly prefer skincare products made from natural ingredients with minimal side effects. In this formulation, avocado is included for its moisturizing and nourishing properties, butterfly pea flower (Clitoria ternatea) for its antioxidant, anti-aging, and anti-inflammatory effects, and carrot seed oil for its sun-blocking and UV-protective qualities. Given the growing demand for natural cosmetic ingredients, this hydrogel formulation presents a timely and appealing skincare solution.

2. MATERIALS AND METHODS

2.1 Materials

2.1.1 Plant Extract

Table 1: Plant Extract

2.1.2 Excipients and Other Materials

Table 2: Excipients and Other Materials

2.2 Equipments

• Digital pH meter
• Spreadability device
• Brookfield Viscometer (model- DVE)
• UV Visible spectrophotometer

2.3 Formulation Table

Table 3: Formulation Table

2.4 Method of Preparation

2.4.1 Extraction Process

Avocado-

Avocado's were procured from local super market (Nashik Maharashtra).

Avocado Seed Extraction: The seeds were separated, finely chopped, and dried in a hot air oven at 60°C. Once dried, they were ground into a fine powder using a blender and passed through an 80-mesh sieve. The resulting powder was macerated in ethanol for 24 hours. The filtrate was then collected and stored for further use^[13][15].

Avocado Peel Extraction: The peels were similarly dried, chopped, and ground into a fine powder, then sieved using an 80-mesh screen. This powder was macerated with ethanol for 24 hours, and the filtrate was collected and stored.

Avocado Pulp Oil: The pulp was separated and dried in a hot air oven at 70°C. After drying, it was crushed, and oil was extracted using the cold press method ^[18].

Blue Butterfly Pea Flower:

Dried Clitoria ternatea flowers were purchased from VEDAYUG (Flipkart store).

Extraction of flower: The powdered flower material was macerated in a hydroethanolic solution (70% ethanol and 30% water by volume) for 48 hours, with occasional shaking to enhance extraction. After filtration, the extract was concentrated using a rotary evaporator under reduced pressure. The crude extract was then stored at 4°C for further analysis^[19].

2.4.2 Preparation of Hydrogel

Extract were dissolved in carbopol base in a beaker and all the extracts were added. It was mixed with the help of magnetic stirrer. Afterwards, excipients were added and the formulation was continuously swirled for 1-2 minutes.

3. EVALUATION PARAMETER

3.1 Physical appearance-

Initial phytochemical screening was conducted on the extracts of all three plants to identify the presence of active constituents ^[20].

3.2 Determination of pH-

To measure the gel's pH, 0.5 grams of the formulation was dissolved in 50 mL of distilled water and analyzed using a digital pH meter. The recorded pH ranged from 5.6 to 6.8, which aligns with the skin's natural pH and is considered suitable for topical application ^[21].

3.3 Spreadability-

Spreadability was evaluated using a specialized apparatus comprising a wooden platform with a scale, two glass slides, and a pulley system with weighted pans. A measured amount of gel was placed between the slides, which were compressed to a uniform thickness under a set weight for a specific time. Spreadability was determined by the time required to separate the two slides—the shorter the time, the better the spreadability. This formula was used to calculate it:

S=M*L/T

Where,

S stands for Spreadability.

M = Weigh connected to the top slide

L = Glass slide length

T = Total time required to divide the slides^[22].

3.4 Non-irritancy Test-

Gel formulations may cause skin irritation or allergic reactions, which is why a patch test was conducted to evaluate dermal compatibility. A square centimeter area was marked on the dorsal side of the left hand, and the gel was applied to this region. Observations were made over a 24-hour period to monitor for signs of erythema, edema, or any irritation. Human volunteers were examined for any adverse skin reactions such as redness, itching, or discomfort following application of the herbal gel ^[21].

3.5 Washability-

To assess washability, a small quantity of the gel formulation was applied to the skin, then rinsed off using warm water. The ease of removal indicated the formulation’s washability. The gel was expected to be easily washable without leaving residue^[14].

3.6 Viscosity-

The viscosity of the gel formulation was evaluated using a Brookfield Viscometer (model DVE) equipped with an LV4 spindle, under controlled temperature conditions.

3.7 Determination of SPF-

The sun protection factor (SPF) of the herbal formulations was evaluated in vitro using a UV-Visible spectrophotometer. A 0.10% (w/v) solution was prepared by dissolving 0.050 g of the herbal sunscreen in 50.0 mL of ethanol. The absorbance of each sample was measured at 5 nm intervals within the 290–320 nm wavelength range^[23]. SPF values were calculated using a standard formula, with each sample tested in triplicate to ensure accuracy.

SPF= CF-ΣΕΕ(λ) × 1(λ) × Α(λ)

Highest limit 320, Lowest limit= 290

Where, CF Correction Factor (10)

EE= Erythemogenic Effect

I=Intensity of Solar Light of wavelength

A =Absorbance

Table 4: Constant Values of EE * I (Normalised)

3.8 Homogeneity-

The homogeneity of the hydrogel was assessed to ensure uniform distribution of all components such as polymers, cross-linkers, and additives throughout the formulation, indicating consistent quality and performance.

4. RESULT AND DISCUSSION

A multifunctional Hydrogel was formulated and evaluated. All the raw materials were sourced, plant extracts were prepared and final formulation was developed.

4.1 Physical Appearance- Nature of Extracts

Table 5: Nature of Extracts

Physical Appearance of hydrogel-

Table 6: Physical Appearance of Gel

The formulation using a carbopol base exhibited a slightly creamy consistency with a dark lavender colour and a rose fragrance, as detailed in Table 6.

4.2 Determination of pH

Table 7: Determination of pH

The pH of the skin is between 4.5-5.5. The formulated gels showed a pH of approximately 6.29, which falls within the acceptable range for topical gels, as shown in Table 7. This mildly acidic pH supports the stability of the herbal ingredients. The pH remained consistent during the observation period, indicating that the formulation possesses good chemical stability.

4.3 Determination of spreadability

Table 8: Spreadability Values

The spreadability of the hydrogel formulation with a Carbopol base was measured and the average spreadability was calculated to be 15.84 gm.cm/sec. The formulation showed good spreadability, indicating ease of application on the skin. A mean value of 15.84 gm.cm/sec falls within an acceptable range for topical preparations, suggesting that the hydrogel is user-friendly and likely to provide uniform coverage when applied.

4.4 Non – irritancy test

The hydro gel was evaluated for skin irritation. No signs of erythema, edema, itching, or irritation were detected.

4.5 Washability

The washability test was performed. Here ease of removal of gel from skin with water was evaluated. The hydrogel demonstrated good washability, confirming that it can be easily cleaned off the skin.

4.6 Viscosity

Table 9: Viscosity

Viscosity generally elaborates on consistency. With increasing polymer concentration, viscosity of gel increases while the spreadability decreases. Carbopol based formulation showed viscosity of 19380cP as mentioned in table 9.

4.7 SPF

a) Carbopol Gel

Table 10: SPF Calculations (Carbopol)

                    F1 =Optimized Batch

UV Spectroscopy was used to determine SPF. Total three batches were evaluated. In the formulations, F1 batch was found to be the Optimised batch with SPF15 as mentioned in table 10. The formulation was found to be stable, homogeneous in nature and no phase inversion was seen.

Fig. 1: Absorbance vs Wavelength

The F1 batch showed the highest absorbance across the UV wavelength range (Fig.1), indicating better UV blocking properties.

Fig. 2 : Product vs SPF