期刊
JOURNAL OF ETHNOPHARMACOLOGY
卷 119, 期 3, 页码 507-512出版社
ELSEVIER IRELAND LTD
DOI: 10.1016/j.jep.2008.06.006
关键词
Antioxidant; L-DOPA; Sideroxylon inerme; Tyrosinase inhibition; Tyrosine
资金
- National Research Foundation [2069379]
- National Research Foundation
Objective: To investigate the stem bark of Sideroxylon inerme Land its compounds for tyrosinase-inhibition activity and to evaluate the mechanism involved of the most potent compounds in tyrosinase inhibition. Materials and methods: Three different extracts (acetone, methanol and dichloromethane) of Sideroxylon inerme L were evaluated for their inhibitory effect in vitro on the monophenolase and diphenolase activated forms of tyrosinase, using a calorimetric procedure. This test was used for bioactivity-guided isolation of two active compounds using column chromatography and TLC. Active extracts were also investigated for their inhibitory effect on melanogenesis in cultured B16 melanoma cells. Antioxidant activities of the methanolic extract of Sideroxylon inerme and purified compounds were investigated using the 1,2-diphenyl-2-picrylhydrazyl (DPPH) antioxidant assay. The inhibition of tyrosinase activity relative to the inhibition of its activity at the transcriptional level was also studied by determination of the degree of expression of mRNAs for this gene by using extract of Sideroxylon inerme-treated cells (B16F10) and semi-quantitative RT-PCR. Results: Methanolic and acetonic extracts of the stem bark of Sideroxylon inerme showed significant inhibition of monophenolase activity (IC50 values of 63 mu g/ml and 82 mu g/ml, respectively). The methanolic extract also exhibited 37% reduction of melanin content at 6.2 mu g/ml in melanocytes without being significantly toxic to the cells. Examination for inhibition of monopherroloxidase in situ on TLC, followed by column chromatographic purification of the stem bark extract of Sideroxylon inerme, resulted in the isolation of two active compounds, epigallocatechin gallate and procyanidin 131, with IC50 values against monopherrolase of 30 mu g/ml and >200 mu g/ml, respectively. Epigallocatechin gallate exhibited a greater anti-tyrosinase activity than arbutin. Sideroxylon inerme bark extracts, epigallocatechin gallate and procyanidin B1 exhibited antioxidant DPPH radical scavenging activities with EC50 values of 1.54 mu g/ml, 1.33 mu g/ml and 1.68 mu g/ml, respectively and were not particularly cytotoxic. During mechanism studies it was evident that at the transcription level, Sideroxylon inerme (25 mu g/ml) was acting as a potent tyrosinase inhibitor compared to controls (untreated cells and kojic acid). Conclusion: The bark extract of Sideroxylon inerme and the two isolated compounds warrant further investigation in clinical studies to be considered as skin-depigmenting agents. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据