Review on Formulation and Evaluation of Polyherbal Sunscreen

Polyherbal formulations, which combine multiple plant extracts, are known to produce synergistic effects that enhance therapeutic efficacy. Many medicinal plants, such as Aloe vera, tea tree oil, butterfly pea flower, rose water, and vitamin E, contain flavonoids, phenolic compounds, and antioxidants that exhibit significant photoprotective properties. These can absorb UV radiation, neutralize free radicals, and prevent oxidative damage to skin cells. Conventional sunscreens often contain synthetic chemicals that may cause allergic reactions, irritation, or environmental harm. Therefore, there is a growing interest in developing herbal or polyherbal sunscreen formulations using natural ingredients that are safe, effective, and biodegradable. Polyherbal formulations combine multiple herbal extracts with complementary properties to enhance the overall sun protection effect. Herbs like Aloe vera, turmeric, green tea, cucumber, and sandalwood possess antioxidant, anti-inflammatory, and UV-protective properties, making them suitable for use in natural sunscreens.

CLASSIFICATION OF SUNSCREENS

Sunscreens are protective agents that help prevent damage to the skin caused by ultraviolet (UV) radiation from the sun. They can be classified in different ways based on their composition, mechanism of action, and the type of UV protection they provide.

1. Based on Mechanism of Action
   1. Physical (Inorganic) Sunscreens

• Also known as sunblock agents.
• They reflect and scatter UV radiation before it penetrates the  skin.
• Usually contain mineral particles that act as physical barriers.
• Provide protection against both UVA and UVB rays.
• Common ingredients:
• Zinc oxide (ZnO)
• Titanium dioxide (TiO?)
• Advantages: Non-irritating, photostable, and suitable for sensitive skin.
• Disadvantages: May leave a white residue and have poor cosmetic appeal.
  2. Chemical (Organic) Sunscreens

• These agents absorb UV radiation and convert it into harmless heat energy
• Different compounds absorb at specific UV wavelengths (UVA or UVB).
• Common ingredients:
• Para-aminobenzoic acid (PABA)
• Oxybenzone Octyl
• Avobenzone
• Advantages: Easy to apply, transparent, and cosmetically elegant.
• Disadvantages: May cause skin irritation or allergic reactions in some users and can degrade upon sunlight exposure (photoinstability).
  3. Combination Sunscreens

• Contain a mixture of physical and chemical agents to provide broad-spectrum protection and improved cosmetic acceptability.
• Example: Formulations combining zinc oxide (physical) and avobenzone (chemical).

IMG 1:  Classification of Sunscreen

Based on Spectrum of Protection

A broad-spectrum sunscreen provides protection against both UVA and UVB rays.

2. Based on Ingredients Source
   1. Synthetic Sunscreens

• Made from laboratory-synthesized organic and inorganic compounds.
• Provide strong protection but may cause side effects with long-term use.
  2. Herbal (Natural) Sunscreens

• Contain plant-based ingredients rich in flavonoids, phenols, and antioxidants that absorb UV radiation naturally.
• Examples: Aloe vera, Green tea, Turmeric, Neem, Cucumber, Sandalwood, and Clitoria ternatea (Butterfly pea flower).
• Safer, biodegradable, and environmentally friendly alternatives.

3. Based on Formulation Type

• Creams: Suitable for dry or normal skin.
• Lotions: Lightweight and easy to spread.
• Gels: Non-greasy, ideal for oily or acne-prone skin.
• Sprays: Convenient for large-area application.
• Sticks: Used for targeted protection (e.g., lips, nose).

SKIN RELATED PROBLEMS IN SUMMER AND THEIR PREVENTION

During the summer season, high temperatures and increased exposure to ultraviolet (UV) radiation can cause various skin problems. The combination of heat, humidity, sweating, and sunlight affects the skin’s natural balance, leading to both short-term and long-term damage. Understanding these issues and their preventive measures is important for maintaining healthy skin.[4]

1. Sunburn

• Cause: Prolonged exposure to UVB rays damages the outer layer of the skin, leading to redness, pain, and inflammation.
• Symptoms: Redness, tenderness, peeling, and burning sensation.  
• Prevention: Apply broad-spectrum sunscreen (SPF 30 or higher) before going outdoors.   Reapply sunscreen every 2–3 hours. Wear protective clothing, hats, and sunglasses.   Avoid direct sunlight between 10 AM to 4 PM.

2. Skin Tanning

• Cause: Overproduction of melanin as a defense mechanism against UV rays.  
• Symptoms: Darkening of the skin or uneven skin tone.
• Prevention: Use sunscreen with both UVA and UVB protection. Apply aloe vera gel, cucumber extract, or lemon juice to help lighten tanned areas naturally.   Exfoliate the skin regularly.

3. Premature Skin Aging

• Cause: Long-term UV exposure leading to breakdown of collagen and elastin fibers in the skin.
• Symptoms: Wrinkles, fine lines, and sagging skin.
• Prevention: Use sunscreens with antioxidants such as vitamin E and green tea extract. Maintain a balanced diet rich in vitamins and minerals. Avoid smoking and dehydration.

4. Skin Dehydration

• Cause: Excess water loss from the skin due to heat exposure.
• Symptoms: Dryness, dullness, tightness, and flaking of skin.
• Prevention: Drink plenty of water and fluids. Apply moisturizers containing aloe vera or glycerin.   Avoid alcohol-based products.

INGREDIENTS & THEIR USES

Here’s a list of ingredients commonly used in the formulation and evaluation of a polyherbal sunscreen cream, including their scientific names, category, and function:

Polyherbal Sunscreen Cream — Ingredients List

FORMULATION METHOD OF SUNSCREEN

The process of formulating a polyherbal sunscreen typically involves herbal extraction, preparing an oil-in-water (O/W) emulsion base, incorporating the extracts and other active ingredients into the emulsion, and finally, evaluating the product for safety, stability, and efficacy.

Step 1: Preparation of Herbal Extracts

• Collection and preparation of plant material: Plant materials (e.g., green tea leaves, turmeric rhizomes) are collected, washed, shade-dried, and then pulverized into a coarse powder.
• Extraction: The powdered material is macerated or refluxed with a suitable solvent (commonly ethanol or water) to extract the active phytochemicals.
• Filtration and Concentration: The extract is filtered, and the solvent is removed (often under reduced pressure using a rotary evaporator) to obtain a concentrated residue or extract, which is then stored for later use.

Step 2: Preparation of the Emulsion Base

• The most common method is the O/W emulsion method, which involves two separate phases:
• Aqueous Phase: Water-soluble components like distilled water, glycerin, preservatives, and the polyherbal extracts are combined in a beaker and heated to a specific temperature, typically around 75°C (167°F).
• Oil Phase: Oil-soluble components, including natural oils (e.g., coconut oil, almond oil, olive oil), emulsifying agents (e.g., stearic acid, cetyl alcohol, beeswax), and other lipophilic substances, are mixed together in a separate beaker and heated to the same temperature as the aqueous phase. Micronized zinc oxide (a natural mineral UV blocker) may also be gradually added to the oil phase with constant stirring to ensure uniform dispersion.

Step 3: Emulsification and Cooling

• Mixing: The preheated aqueous phase is gradually added to the oil phase under continuous, high- speed stirring or homogenization.
• Cooling: The mixture is continuously stirred until a homogeneous emulsion forms and it cools down to room temperature (around 25°C).
• Addition of Final Actives and pH Adjustment: Once the temperature reaches around 40°C, temperature-sensitive ingredients like vitamin E or specific essential oils are added. The pH of the final product is adjusted to be skin-compatible (usually between 5.5 and 6.5) using an agent like triethanolamine (TEA) or sodium hydroxide solution.

Step 4: Packaging and Evaluation

• Packaging: The finished polyherbal sunscreen is transferred into clean, opaque containers to protect it from light and prevent contamination.
• Evaluation: The final product undergoes various quality control tests, including:   Physical appearance: Checking color, odor, consistency, and homogeneity.
• pH measurement: Ensuring it is within the skin-compatible range.
• Spreadability and viscosity: Assessing how easily the product applies to the skin.
• Stability testing: Performing accelerated tests like centrifugation or thermal cycling to check for phase separation.
• In vitro SPF determination: Calculating the Sun Protection Factor using spectrophotometric methods and specific equations (e.g., Mansur equation).
• Safety testing: Conducting irritancy patch tests on the skin to ensure the product is safe for use.

A polyherbal sunscreen cream is formulated using an emulsification process that combines oil and aqueous phases :

1. Prepare the Oil Phase: Combine lipophilic (oil-loving) ingredients like beeswax, cetostearyl alcohol, liquid paraffin, or specific oils in a beaker. Heat the mixture on a water bath until melted and homogenous.
2. Aqueous Phase: In a separate container, mix hydrophilic (water-loving) ingredients such as distilled water, glycerin, and water-soluble components like preservatives. Heat this mixture on a water bath to a similar temperature as the oil phase (e.g., \(70-75^{\circ }C\)).
3. Emulsify the mixture Slowly and gradually add the hot aqueous phase to the hot oil phase with constant stirring.Continue stirring until the mixture becomes a uniform and homogeneous emulsion, which will start to congeal as it cools to room temperature.
4. Incorporate herbal extracts and finish Once the base has cooled, stir in the herbal extract(s) or other active ingredients, ensuring they are thoroughly mixed.Add final ingredients like perfume or coloring agents at this stage, if applicable.Pour the finished cream into an airtight container and allow it to condition for at least 24 hours before evaluation or use.

RESULTS

1. Physical Appearance and Organoleptic Properties

The prepared polyherbal sunscreen cream appeared smooth, soft, and homogeneous with a light purple color attributed to the presence of butterfly pea flower extract. It had a pleasant rose fragrance and a non-greasy texture, indicating proper emulsification. No signs of phase separation, grittiness, or air entrapment were observed during storage, confirming the stability and good aesthetic quality of the formulation.

2. Evaluation Parameters