Abstract

• The present study was conducted to investigate bioactive chemical constituent from Myanmar medicinal plant, Orthosiphon rubicundus (D.Don) Benth. Firstly, phytochemical screening of the selected medicinal plant was performed according to standard procedure. Then, the antimicrobial assay of various extracts was performed on six test microorganisms. Phenylnaphthalene derivative namely, 1-(4-hydroxy-3,5-dimethoxyphenyl)-2,3-dimethyl-5,6,7-trimethoxynaphthalene (1) was isolated from ethyl acetate extract by using separation techniques such as thin layer and column chromatographic methods. Moreover, the antioxidant activities of crude extract and isolated compound were evaluated using DPPH radical scavenging assay. Furthermore, structure elucidation of isolated compound was performed by spectroscopic techniques, particularly by 1D and 2D NMR spectroscopy.