This fraction showed the highest antioxidant activity by dose-dependent free radical scavenging action (IC50 ± µg/mL). R. tomentosa leaf extracts, especially the n-hexane fraction, also exhibited strong antimicrobial activity against Gram-negative and Gram-positive bacteria and fungi as well as moderate inhibitory effect on L-DOPA (L-3,4-dihydroxyphenylalanine) oxidase activity of tyrosinase in the melanin biosynthesis pathway. | JOURNAL OF SCIENCE OF HNUE Chemical and Biological Sci. 2013 Vol. 58 No. 9 pp. 123-131 This paper is available online at http PHYTOCHEMICAL CONSTITUENTS AND ANTIOXIDANT ANTIMICROBIAL AND ANTIMELANOGENIC ACTIVITIES OF Rhodomyrtus tomentosa AITON HASSK. LEAF EXTRACT Le Thi Phuong Hoa and Hoang Thi Nga Faculty of Biology Hanoi National University of Education Abstract. The antioxidant antimicrobial and antimelanogenic activities of various leaf extracts of Rhodomyrtus tomentosa Aiton Hassk. were investigated together with their phytochemical constituents. Among the extracts the ethyl acetate fraction had the highest level of phenolics and flavonoids mg gallic acid equivalent g of extract and mg quercetin equivalent g of extract . This fraction showed the highest antioxidant activity by dose-dependent free radical scavenging action IC50 µg mL . R. tomentosa leaf extracts especially the n-hexane fraction also exhibited strong antimicrobial activity against Gram-negative and Gram-positive bacteria and fungi as well as moderate inhibitory effect on L-DOPA L-3 4-dihydroxyphenylalanine oxidase activity of tyrosinase in the melanin biosynthesis pathway. Further work is suggested to characterize bioactive compounds from ethyl acetate and n-hexane fractions for use in pharmaceutical applications especially in skin care. Keywords Rhodomyrtus tomentosa antioxidant antimicrobial antimelanogenic. 1. Introduction In recent years the search for natural sources for bioactivities such as antioxidant and antimicrobial properties has been rising with the global concern for preventive healthcare and the problem of drug-resistant bacteria. In Vietnam as in other tropical South East Asian countries there is high diversity of plants among which a number have traditionally been used to treat ailments and as food. Rhodomyrtus tomentosa Aiton Hassk. commonly known as rose myrtle or sim in Vietnamese is an evergreen shrub abundant in the .
