Anthraquinone-Based Specialized Metabolites from Rhizomes of Bulbine natalensis.

The rhizomes of Bulbine natalensis furnished six previously unreported anthraquinone derivatives (1-6), together with eight known specialized metabolites. Their structures were determined by interpretation of 1D and 2D NMR and HRESIMS data. The absolute configurations of compounds 1-6 were determined by specific rotation and circular dichroism experiments. The isolated compounds were evaluated for antimicrobial activities, and compound 1 was found to be a moderate inhibitor (IC50 0.02 μM) against methicillin-resistant Staphylococcus aureus (MRSA).