Chemical constituents and chemotaxonomic study on the marine actinomycete Williamsia sp. MCCC 1A11233

•It’s the first report of chemical constituents on Williamsia species.•One new and 23 known compounds were obtained.•Structure elucidation achieved mainly by analysis of NMR spectroscopic data.•2-Aminobenzoic acid derivatives might be chemotaxonomic markers for Williamsia species.

The marine actinomycete Williamsia sp. MCCC 1A11233 was isolated from a deep sea sediment sample of the southwestern Indian Ocean. It was closely related to Williamsia limnetica L1505T with a 16S rRNA gene sequence similarity value of 99.2%. A systematic investigation on its chemical constituents was performed in this study, which led to the isolation of one new (1) and 23 known (2–24) secondary metabolites. By mainly detailed analysis of the 1D and 2D NMR spectroscopic data and comparisons with the published data, the chemical structure of 1 was determined to be 3-benzyl-3α,4β-dihydroxypentan-2-one. Noteworthily, the question on which family Williamsia species should belong to was left unsolved at the first beginning when it was found in 1999. Interestingly, the result of this investigation consolidated that Williamsia should be placed a chemotaxonomic position in Nocardiaceae Family. Furthermore, 2-aminobenzoic acid derivatives (8–10) could be taken as chemotaxonomic markers for the genus of Williamsia.