Bioactive homogentisic acid derivatives from fruits and flowers of Miliusa velutina.

Chromatographic separation of fruits and flowers of the Thai medicinal plant, Miliusa velutina, resulted in the isolation of five new rare homogentisic acid derivatives, miliusanal (1) and miliusanones A-D (2-5), together with fifteen known secondary metabolites (6-20). Their structures were determined through the use of extensive spectroscopic data. The absolute configurations of homogentisic acid derivatives 2-7 were identified using NOESY data and a comparison of experimental and calculated ECD spectral data. Compounds 2, 3, 6, and 7 showed antimalarial activity with IC₅₀ values in the range of 3.3-5.2 μg/mL. Compound 6 also showed activity against Mycobacterium tuberculosis with an MIC value of 50 μg/mL. Compounds 1-3, 6 and 7 exhibited cytotoxicity againt KB, MCF-7, NCI-H187 and Vero cell lines with IC₅₀ values in the range of 5.8-40.4 μg/mL. In addition, compounds 1, 2 and 6 showed moderate antibacterial activities against three Gram-positive bacteria (Bacillus cereus, Staphylococcus aureus, and Methicillin resistant S. aureus) with MICs in the range of 32-64 μg/mL.