Objective To investigate the chemical constituents of the leaves of Tectona grandis, and search for antifungal active ingredients. Methods The compounds were obtained by silica gel, MCI, and prep-HPLC column chromatography. Their structures were identified by HRESIMS, IR, 1D- and 2D NMR analysis. The isolates were tested for their antifungal activity by 96 well plate microbroth dilution method. Results Two new naphthoquinones, (E)-2,5,8-trihydroxy-3-(4-acetoxy-3-methylbut-2-en-1-yl)-1,4-naphthoquinone (1) and (E)-2,5,8-trihydroxy-3-(4-hydroxy-3-methylbut-2-en-1-yl)-1,4-naphthoquinone (2), were isolated from the 90% MeOH extract of the leaves of T. grandis. Compounds 1 and 2 exhibited significant antifungal activity when combined with fluconazole, against fluconazole-resistant Candida albicans with MIC₅₀ values of 3.28 and 5.32 μg/mL, respectively. Conclusion Compounds 1 and 2, named tectonagrandiones A and B, were two new naphthoquinones, and the naphthoquinones might be the active antifungal constituents from T. grandis.

Tectona grandis L.  /  Verbenaceae  /  naphthoquinones  /  antifungal activity  /  tectonagrandiones A  /  tectonagrandiones B