Commonly consumed fruits showed remarkable variation in antimutagenicity when assayed by E. coli rifampicin resistance assay, and Java plum (Syzygium cumini) was found to be one of the most potent fruits. Its anthocyanins contributed maximally to the observed antimutagenicity and resolved into three distinct bands in HPTLC. Although these bands displayed similar antioxidant capacity, the band at R(f) 0.22 was the most antimutagenic and resolved into two peaks in HPLC. The second peak (t(R) 3.8 min) displayed a strong and broad spectrum antimutagenicity and was identified as petunidin-3,5-diglucoside by analysis of its molecular ion and fragmentation pattern by ESI-MS/MS. The presence of glucose moiety was confirmed by TLC analysis of acid-hydrolyzed products. This purified anthocyanin was found to suppress mutagenic SOS DNA repair process in E. coli and thus indicated suppression of the error-prone DNA repair pathway as one of the major mechanisms of antimutagenicity of this fruit.