JNTU B.Pharmacy III COSMETIC SCIENCE Previous Question Paper (October/November-2020 - R17)

The physical and chemical properties of hair dictate the formulation requirements for cosmetic products to ensure efficacy and safety. Physically, hair is composed of the cuticle, cortex, and medulla. The cuticle acts as a protective barrier; products like conditioners must be formulated to smooth these scales to improve shine and manageability. The porosity of the hair, which is its ability to absorb moisture, determines the concentration of active ingredients; high-porosity hair requires more intensive moisturizing agents, while low-porosity hair needs lighter, penetrating formulations.

Chemically, hair is primarily composed of keratin, a protein rich in sulfur-containing amino acids like cysteine, which form disulfide bonds. These bonds provide hair with its structural strength and shape. Chemical treatments, such as perms or relaxers, are designed to break and reform these bonds. Therefore, cosmetic chemists must balance the pH of products to maintain the integrity of these bonds; an alkaline pH (above 7) swells the hair shaft to allow dye penetration, whereas an acidic pH (around 4.5 to 5.5) helps close the cuticle and lock in moisture. Understanding the isoelectric point of hair (approximately pH 3.67) is crucial for preventing excessive damage during formulation.

Antioxidants are essential in cosmetic preparations to prevent the degradation of active ingredients and to protect the skin from oxidative stress caused by free radicals. Cosmetics containing unsaturated oils, fats, or vitamins are susceptible to lipid peroxidation, a process catalyzed by light, heat, and oxygen that leads to rancidity, off-odors, and loss of product potency. By incorporating antioxidants, formulators extend the shelf life of the product and maintain its aesthetic and functional quality.

Antioxidants function by donating electrons to neutralize free radicals, thereby terminating chain reactions. Common examples include:

• Tocopherol (Vitamin E): A potent fat-soluble antioxidant that protects oils and fats within the formulation from oxidation and provides skin-conditioning benefits.
• Ascorbic Acid (Vitamin C): A water-soluble antioxidant that prevents the oxidation of aqueous-phase ingredients and is widely used in anti-aging products to promote collagen synthesis.
• Butylated Hydroxytoluene (BHT): A synthetic antioxidant frequently used in low concentrations to stabilize cosmetic formulations against atmospheric oxidation.
• Green Tea Extract: Rich in polyphenols, it serves as a natural antioxidant to protect the skin from UV-induced oxidative damage.

In summary, antioxidants are justified not only for preserving the chemical stability of the cosmetic matrix but also for their therapeutic role in neutralizing reactive oxygen species on the skin surface, which contributes to the prevention of premature aging.