Warmingiins A and B, two new dimeric naphthoquinone derivatives from sinningia warmingii (Gesneriaceae)

Abstract

Chemical investigation of Sinningia warmingii (Gesneriaceae) tubers lead to the isolation of two new dimeric naphthoquinone derivatives, named warmingiins A and B, besides six known compounds, aggregatin E, aggregatin F, tectoquinone, halleridone, cleroindicin B, and cornoside. All compounds were identified by spectroscopic analysis, mainly nuclear magnetic resonance (NMR) and mass spectrometry (MS), and comparison with the literature. The structure of the warmingiin A, which is an artifact of warmingiin B, was confirmed by X-ray diffraction analysis. Antimicrobial activity of the ethanolic extract and fractions of S. warmingii was evaluated against Staphylococcus aureus, S. epidermidis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, C. dubliniensis, C. glabrata and C. parapsilosis. All samples were inactive.