Tyrosinase Inhibitory Activities of Carissa opaca Stapf ex Haines

Objective: Carissa opaca is a medicinal plant with rich folkloric applications. The present research was conducted to explore the tyrosinase inhibitory potential of aqueous decoction (AD) and methanolic extract (ME) of roots of C. opaca and its fractions in various solvents and their phytochemical analysis. Materials and Methods: AD of the dried powdered roots of C. opaca was prepared by boiling in water. ME was prepared by cold maceration. Its fractions were obtained in solvents of increasing polarity, i.e., hexane, chloroform, ethyl acetate, n‑butanol, and water. The biomass left after extraction with methanol was boiled in water to get its decoction Biomass aqueous decoction (BAD). Tyrosinase inhibitory activities of the samples were studied according to a reported method. Chemical compounds in the samples were identified by gas chromatography‑mass spectrometry (GC‑MS). Results: The AD, BAD, and ME and its fractions displayed remarkable tyrosinase inhibitory activity. The IC50 of AD was 23.33 µg/mL as compared to 15.80 µg/mL of the standard arbutin and that of BAD was 21.24 µg/mL. The IC50 of ME was 34.76 µg/mL while that of hexane, chloroform, ethyl acetate, n‑butanolic, and aqueous fractions was 21.0, 44.73, 43.40, 27.66, and 25.06 µg/mL, respectively. The hexane fraction was thus most potent followed by aqueous fraction. By phytochemical analysis, campesterol, stigmasterol, gamma‑sitosterol, alpha‑amyrin, 9,19‑cyclolanostan‑3‑ol, 24‑methylene‑,(3 β)‑, lupeol, lup‑20(29)‑en‑3‑one, lup‑20(29)‑en‑3‑ol, acetate,(3 β)‑, 2(1H) naphthalenone, 3,5,6,7,8,8a‑hexahydro‑4,8a‑dimethyl‑6‑(1‑methylethenyl)‑, and 2,3,3‑trimethyl‑2‑(3‑methylbuta‑1,3‑dienyl)‑6‑methylenecyclohexanone were identified in the extracts by GC‑MS. Other compounds included fatty acids and their esters. Some of these compounds are being first time reported here from this plant. Conclusions: The roots extracts exhibited considerable tyrosinase inhibitory activities, alluding to a possible application of the plant in cosmetic as whitening agent subject to further pharmacological studies.