Three new quinones from Senna pluribracteata (Fabaceae) and investigation of their bioactivity in BV-2 microglial cells

Three new quinones were isolated from Senna pluribracteata, identified as sennaquinone A (1), quinquangulin-6-O-[α-L-rhamnopyranoside-(1→6)-β-D-glucopyranoside] (2) and rubrofusarin-6-O-[β-(6'-(E)-crotonylglucopyranoside] (3), and nine other known compounds identified as quinquangulone (4) rubrofusarin-6-O-[α-L-rhamnopyranoside-(1→6)-β-D-glucopyranoside] (5), norrubrofusarin-6-O-β-D-glucopyranoside (cassiaside) (6), rubrofusarin-6-O-β-D-glucopyranoside (7), vanillic acid (8), protocatechuic acid (9), quercetin-3-O-sambubioside (10), resveratrol (11), and vomifoliol (12). These compounds were determined by HR-ESI-MS, 1D and 2D NMR analyses and ECD calculation. The cytotoxicity of compounds 1, 2, and 3 was first assessed in BV-2 microglial cell line by MTT assay. Compounds 2 and 3 reduced cell viability by more than 20% only at 200 μM, while compound 1 was less cytotoxic. For anti-neuroinflammatory activity evaluation, LPS/IFN-γ co-stimulated microglial cells were treated with non-cytotoxic concentrations (25, 50, and 100 μM) of compounds 1, 2, and 3, and NO production was determined by the Griess method. Our results showed that none of the three compounds reduced NO production, suggesting no anti-neuroinflammatory activity.