Retinyl propionate is a synthetic derivative of a Vitamin A. Upon topical application, retinyl propionate is hydrolyzed by esterases to retinol, which is ultimately converted to retinoic acid. In mouse models, retinyl propionate induced epidermal thickening in mouse tail and promoted collagen formation in UV-irradiated mice. These results encouraged clinical trials of retinyl palmitate against photoaging. Topical retinyl propionate cream (0.15%) did not demonstrate any statistically significant improvement over placebo, but in later studies of combinations of retinyl propionate with climbazole or niacinamide improvements in the appearance of fine lines, wrinkles and age spots were demonstrated.

4-Carvomenthenol (Terpinen-4-ol) is an anti-inflammatory and antimicrobial agent. 4-Carvomenthenol is a fragrance ingredient used in decorative cosmetics, fine fragrances, shampoos, toilet soaps and other toiletries as well as in non-cosmetic products such as household cleaners and detergents. Its use worldwide is in the region of 1–10 metric tonnes per annum. The maximum skin level that results from the use of 4-carvementhenol in formulae that go into fine fragrances has been reported to be 0.13%. 4-Carvomenthenol has been shown to have antiviral, antibacterial, antifungal, and insecticidal effects as well as antioxidant and anti-inflammatory activities. It is a putative anitcancer agent. 4-carvementhenol exerts its antitumor effects by triggering caspase-dependent apoptosis in human melanoma cells or by inducing necrotic cell death and cell-cycle arrest in mouse mesothelioma and melanomacell lines without affecting normal cells. Caspase-dependent mitochondrial dysfunction is the mechanism of terpinen-4-ol-induced apoptosis in nonsmall lung cancer cells. Down-regulation of Bcl-2, XIAP and survivin suggests that ter-pinen-4-ol increases the susceptibility of NSCLC cells toapoptosis induction. Notably, the ability of terpinen-4-ol to induce apoptosis in NSCLC cells is p53-dependent. It has also been shown that the growth of s.c. xenograft tumors was remarkably inhibited by intratumoral injection of terpinen-4-ol, indicating that the agent also has potential for clinical anticancer activity.