Antimicrobial Acylphloroglucinol Meroterpenoids and Acylphloroglucinols from Dryopteris crassirhizoma

Ten novel meroterpenoids, dryoptins/11 ''-epi-dryoptins A similar to E (1 similar to 10 ) with an unprecedented skeleton consisting of dimeric or trimeric acylphloroglucinols and dehydrotheonelline, two undescribed acylphloroglucinol-nerolidol meroterpenoids (11 similar to 12 ), and ten known acylphloroglucinol derivatives (13 similar to 22 ), were isolated from D. crassirhizoma. The novel structures including absolute configurations were established by comprehensive spectroscopic analyses and quantum chemical electronic circular dichroism (ECD) calculations. A biosynthetic pathway of 1 similar to 10 was assumed. The trimeric acylphloroglucinol meroterpenoids 7 / 8 showed significant antifungal activity against standard Candida albicans with a MIC50 value of 1.61 mu g/mL [fluconazole (FLC): 3.41 mu g/mL], and when combined with FLC, the principal components 20 and 21 exhibited strong antifungal activities against FLC-resistant C. albicans with MIC (50) values of 8.39 and 7.16 mu g/mL (FLC: > 100 mu g/mL), respectively. Moreover, compounds 2, 5 / 6, 18, 19 , and 21 exhibited inhibitory effects against several pathogenic fungi and bacteria, with MIC50 values of 6.25 similar to 50 mu g/mL.

Automated summary

Novel meroterpenoids with unique structures were isolated from D. crassirhizoma, showing promising antifungal and antibacterial activities, indicating their potential as drug candidates.