Transformations of Some Sesquiterpene Lactones by Filamentous Fungi and Cytotoxic Evaluations

Biotransformation is an economically and ecologically viable technology which has been used to modify the structures of many classes of biologically active products. Some fungi may be useful for the biotransformation of sesquiterpene lactones (SLs), leading to unusual structural changes that modify their biological activities, and other transformations mimic their biosynthetic pathways, generating evidences for the proposed biogenesis. Eight filamentous fungi were screened for their ability to transform different SLs (1 - 9), and microbial reactions yielded compounds 10 - 17, which in turn have been isolated as natural products, thus mimicking their biosynthesis. Their structures were identified based on NMR and MS spectroscopic analyses. The cytotoxicities of SLs 1, 4, 6, 7 and 9, and their biotransformed produts (10, 14, 15 and 17) against human cancer cell lines U251 (glia), PC3 (prostate), K562 (leukemia), HCT-15 (colon), MCF7 (breast), and SKLU-1 (lung), were determined, confirming that the presence of Michael acceptor is an important feature for the bioactivity.