The methanol extract of P. palatiferum (Nees) Radlk. leaves exhibited a moderate inhibitory effect on the L-3,4-dihydroxyphenylalanine (L-DOPA) oxidase activity of tyrosinase in the melanin biosynthesis pathway. Further study may lead to new bioactive compounds from ethyl acetate and n-hexane fractions. | JOURNAL OF SCIENCE OF HNUE Chemical and Biological Sci. 2014 Vol. 59 No. 9 pp. 103-113 This paper is available online at http PHYTOCHEMICAL CONSTITUENTS AND BIOLOGICAL ACTIVITIES OF Pseuderanthemum palatiferum Nees Radlk. LEAF EXTRACTS Le Thi Phuong Hoa and Pham Thi Diu Faculty of Biology Hanoi National University of Education Abstract. Total methanol extract and n-hexane ethyl acetate and water fractions of P. palatiferum Nees Radlk. leaves were investigated for their antioxidant antimicrobial and tyrosinase inhibitory activities in correlation with their phytochemical constituents. Of the extracts the ethyl acetate fraction had the highest level of phenolics mg gallic acid equivalents g of extract more than half of which were flavonoids mg quercetin equivalents g of extract confirming the result of thin layer chromatography analysis. Ethyl acetate and water fractions had antioxidant activity by dose-dependent 1 1-diphenyl-2-picryl hydrazyl DPPH radical scavenging action IC50 and µg mL respectively which closely correlated with the total phenolic content R2 . P. palatiferum leaf extracts showed stronger antibacterial activity against Escherichia coli and Bacillus subtilis than Staphylococcus aureus. Only the n-hexane fraction showed inhibitory activity on Pseudomonas sp. and Candida sp. The methanol extract of P. palatiferum Nees Radlk. leaves exhibited a moderate inhibitory effect on the L-3 4-dihydroxyphenylalanine L-DOPA oxidase activity of tyrosinase in the melanin biosynthesis pathway. Further study may lead to new bioactive compounds from ethyl acetate and n-hexane fractions. Keywords Pseuderanthemum palatiferum antioxidant antimicrobial tyrosinase inhibitory activity. 1. Introduction Pseuderanthemum palatiferum Nees Radlk. or Hoan ngoc in Vietnamese is a medicinal plant of the Acanthaceae family. It was first found in the Cuc Phuong forest in northern Vietnam in the latter half of the .
