Tracking leading anti-Candida compounds in plant samples; Plumbago europaea

Background and Objectives: Due to the importance of finding new and more effective antifungal and antibacterial compounds against invasive vaginitis strains, this study was conducted for fast screening of plant samples. Materials and Methods: Thirty Iranian plant samples were successively extracted by n-hexane, ethyl acetate and methanol to obtain a total of 90 extracts. Each extract was prepared in six concentrations and evaluated for antifungal activity via a micro-broth dilution method. Further phytochemical study of the aerial parts of Plumbago europaea, as the most promising source of anti-Candida compounds (with minimum inhibitory concentration of about 7μg/ml), was carried out and antifungal activity in the ethyl acetate extract was tracked using a combination of HPLC time-based fractionation and Thin Layer Chromatography-Bioautography via a bioassay-guided fractionation procedure. The compounds in the active region of the chromatogram were purified by a combination of column chromatography and preparative TLC, and then structure elucidation was achieved by 1D and 2D NMR, mass spectrometry and UV spectra. Results: Seven compounds were isolated and identified: (1) plumbagin, (2) isoplumbagin, (3) 5, 8-dihydroxy-2-methyl-[1, 4] naphthoquinone, (4) droserone, (5) 7-methyljuglone, (6) Isozeylanone, and (7) methylene-3, 3’-diplumbagin. Antimicrobial activity of the purified compounds were also evaluated against C. albicans (MIC values ranging from 2 to 2500 μM) and Gardnerella vaginalis (MIC values ranging from 20 to 2500 μM). Conclusion: These naphthoquinone compounds could be surveyed for finding new and more effective anti-vaginitis agents via drug design approaches.