New antifungal steroids from<i>Turbinaria conoides</i>(J. Agardh) Kutzing

Abstract

Two new steroids 3,6,17-trihydroxy-stigmasta-4,7,24(28)-triene (1) and 14,15,18,20-diepoxyturbinarin (3), together with a known compound, fucosterol (2), were isolated from the cyclohexane extract of Turbinaria conoides. The structures were elucidated on the basis of spectroscopic evidence. The isolated compounds were screened against a panel of microorganisms. Minimum inhibitory concentrations (MICs) were determined by the standard broth dilution method. Compounds 1-3 exhibited moderate antibacterial activity against the tested bacteria and inhibited the fungal growth with MIC values ranging from 2 to 16 microg mL(-1). Compound 3 was found to be most potent against Aspergillus niger, with an MIC value of 2.0 microg mL(-1). The isolation of antifungal compounds from T. conoides is reported for the first time. These results suggested that 14,15,18,20-diepoxyturbinarin (3) could be developed as a new lead antifungal agent.