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

Three new quinones were isolated from <i>Senna pluribracteata</i>, identified as sennaquinone A (<b>1</b>), quinquangulin-6-<i>O</i>-[α-L-rhamnopyranoside-(1→6)-β-D-glucopyranoside] (<b>2</b>) and rubrofusarin-6-<i>O</i>-[β-(6'-(<i>E</i>)-crotonylglucopyranoside] (<b>3</b>), and nine other known compounds identified as quinquangulone (<b>4</b>) rubrofusarin-6-<i>O</i>-[<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>α</mml:mi></mml:mrow></mml:math>-L-rhamnopyranoside-(1→6)-β-D-glucopyranoside] (<b>5</b>), norrubrofusarin-6-<i>O</i>-β-<i>D</i>-glucopyranoside (cassiaside) (<b>6</b>), rubrofusarin-6-<i>O</i>-β-D-glucopyranoside (<b>7</b>), vanillic acid (<b>8</b>), protocatechuic acid (<b>9</b>), quercetin-3-<i>O</i>-sambubioside (<b>10</b>), resveratrol (<b>11</b>), and vomifoliol (<b>12</b>). These compounds were determined by HR-ESI-MS, 1D and 2D NMR analyses and ECD calculation. The cytotoxicity of compounds <b>1</b>, <b>2</b>, and <b>3</b> was first assessed in BV-2 microglial cell line by MTT assay. Compounds <b>2</b> and <b>3</b> reduced cell viability by more than 20% only at 200 μM, while compound <b>1</b> 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 <b>1</b>, <b>2</b>, and <b>3</b>, 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.