Sesquiterpenes from Carpesium macrocephalum inhibit Candida albicans biofilm formation and dimorphism.

One new xanthanolide, 4-(2-methybutyryl)-4H-tomentosin (1) was isolated from the whole plant of Carpesium macrocephalum together with nine known sesquiterpenes (2-10), including four eudesmane sesquiterpenes (2, 4, 5, and 10), one guaianolide (3), two xanthanolides (6 and 9) and two carabranolides (7 and 8). Their structures were elucidated on the basis of detailed spectroscopic analyses. All isolates were evaluated for their antifungal activities against the growth, biofilm formation and yeast-hyphal transition in Candida albicans. All compounds lacked the antifungal activity (MIC50>256 μg/ml) except compound 6 with the MIC50 value of 128 μg/ml. However, compounds 3, 5 and 10 strongly inhibited biofilm formation with IC50 values ranging from 15.4 to 38.0 μg/mL, and compounds 1, 3, 4, 6 and 7 inhibited the yeast-to-hyphae morphogenetic transition with the IC50 values between 31.6 and 118.4 μg/mL. The above results indicated that sesquiterpenes from C. macrocephalum may have therapeutic potential for candidiasis as virulence inhibitors.