Natural products from the culture broth of an actinobacteria Streptomyces sp. M5205 and evaluation of their antifungal activity

One previously undescribed sesquiterpene analog, M5205 (1), together with four known analogs, betulinic acid (2), betulin (3), messagenic acid D (4), and betulonic acid (5), were isolated from the EtOAc extract of the culture broth of the actinomycete Streptomyces sp. M5205. The structures of all isolates were elucidated on the basis of extensive analyses of spectroscopic data and comparison with literature data. Their antifungal activity was also evaluated. Our results showed that 4 constituents (Compounds 1 & 3-5) possessed mild antifungal activity against Fusarium sp. LC8, Neopestalotiopsis sp. BCRC 35002, and Colletotrichum gloeosporioides BCRC 35178. It is worth mentioning that the chemical composition of the type strain Streptomyces sp. M5205 has never been studied.