A test had been conducted for isolation and identification of the active compound from ethylacetate fraction of casturi (Mangifera casturi Konsterm.) fruit. The ethylacetate fraction was obtained from methanolic extract of casturi that had been extracted using n-hexane; n-hexane insoluble extract was re-extracted using ethylacetate (ethylacetate soluble extract is called ethylacetate fraction). Extraction was conducted using liquid-liquid method. The compound was isolated using column chromatograph with n-hexane-ethylacetate as solvents at gradients of (10:1, 8:2, 6:4, 5:5, 4:6, 2:8) v/v and 100% ethylacetate. The isolate was white crystal with melting point ranging from 189 - 1900C. Identification of the isolate was conducted with spectroscopic analyses of UV-Vis, FT-IR, 1HNMR, 13CNMR, DEPT, and LCMS. The identification found a polyphenol compound, namely, 3,4,5-trihydroxy-benzoic acid methyl ester (methyl gallate). Keyword : Mangifera casturi Konsterm, ethyl acetat fraction, isolate, 3,4,5-trihydroxybenzoic acid methyl ester