Phytochemical constituents and biological activities of Pseuderanthemum palatiferum (Nees) Radlk. leaf extracts

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.
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Phytochemical constituents and biological activities of Pseuderanthemum palatiferum (Nees) Radlk. leaf extracts JOURNAL OF SCIENCE OF HNUE Chemical and Biological Sci., 2014, Vol. 59, No. 9, pp. 103-113 This paper is available online at http://stdb.hnue.edu.vn 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 (327.00 ± 56.30 mg gallic acid equivalents/g of extract), more than half of which were flavonoids (182.77 ± 14.37 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 = 90.01 ± 4.12 and 82.36 ± 2.38 µg/mL, respectively), which closely correlated with the total phenolic content (R2 = 0.936). 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 1990s. It is a shrub with a height of 1 to 2 m, multi-branched and rapid growing [6]. Since its discovery, it has been cultivated throughout Vietnam and has been used for both the prevention and treatment Received November 21, 2014. Accepted December 14, 2014. Contact Le Thi Phuong Hoa, e-mail address: lephhoa@yahoo.com 103 Le Thi Phuong Hoa and Pham Thi Diu of human diseases such as hypertension, diarrhea, arthritis, pharyngitis, gastritis tumor, colitis, bleeding, wounds and stomachache [6]. It is also suggested to be applied in husbandry as in raising piglets for increasing growth rate, decreasing mortality and lower the incidence and duration of diarrhea [7]. A phytochemical analysis showed that P. palatiferum leaves are composed of β-sitosterol, stigmasterol, terpenoids, phenolics and flavonoids as well as the essential amino acids lysine, methionine and threonine [5, 6, 10]. Extracts of P. palatiferum leaves have been shown to be capable of biological activities. Ethyl acetate and n-butanol extracts of P. palatiferum leaves had antioxidant activities on blood peroxidase along with antibacterial and antifungal activity [8]. P. palatiferum leaf aqueous extract had acetylcholinesterase inhibitory activity in albino rats [3], antidiabetic activity in decreasing blood glucose in diabetic rats and in vitro antioxidant activity with radical scavenging activity, reducing power, lipid peroxidation inhibition and protective effects against 2-amidinopropane hydrochloride-induced hemolysis [4]. Methanol, ethanol and acetone extracts of P. palatiferum leaves also exhibited antioxidant activity with DPPH scavenging capacity, reducing power and metal chelating activity [10] as well as antibacterial and antifungal activity but at a moderate level [11]. Ethanol extract of P. palatiferum leaves showed significant anti-inflammatory activities against both acute and chronic inflammation using the ethyl phenyl propionate induced ear edema test and the cotton pellet induced granuloma model in albino rats [9]. Ethanol and water extracts of P. palatiferum leaves had antioxidant properties, in decreasing tert-butyl hydroperoxide-induced oxidative stress, and anti-inflammatory properties suppressing LPS plus IFN-γ-induced nitric oxide and the expression of inducible nitric oxide synthase and cyclooxygenase-2 protein levels in RAW264.7 macrophage cells [14]. However, the phytochemical constituents of P. palatiferum leaves in different extraction approache ...