Abstract
Cytochalasans have continuously aroused considerable attention among the chemistry and pharmacology communities due to their structural complexities and pharmacological significances. Sixteen structurally diverse chaetoglobosins, 10-(indol-3-yl)-[13]cytochalasans, including a new one, 6-O-methyl-chaetoglobosin Q (1), were isolated from the coral-associated fungus Chaetomium globosum C2F17. Their structures were accomplished by extensive spectroscopic analysis combined with single-crystal X-ray crystallography and ECD calculations. Meanwhile, the structures and absolute configurations of the previously reported compounds 6, 12, and 13 were confirmed by single-crystal X-ray analysis for the first time. Chaetoglobosins E (6) and Fex (11) showed significant cytotoxicity against a panel of cancer cell lines, K562, A549, Huh7, H1975, MCF-7, U937, BGC823, HL60, Hela, and MOLT-4, with the IC50 values ranging from 1.4 μM to 9.2 μM.
Highlights
Corals generally constitute a dominant part of the reef biomass in tropical marine ecosystems, which are known to harbor diverse and highly abundant microbial communities such as fungi, bacteria, actinomycetes, and cyanobacteria [1]
The rice fermentation broth of C. globosum C2F17 was extracted with EtOAc for three times
The HPLC-DAD-guided purification led to the discovery of 16 diversified chaetoglobosin derivatives (Figure 1)
Summary
Corals generally constitute a dominant part of the reef biomass in tropical marine ecosystems, which are known to harbor diverse and highly abundant microbial communities such as fungi, bacteria, actinomycetes, and cyanobacteria [1]. Coral-associated microorganisms have been considered to be extraordinary sources of bioactive natural products, such as phenolics, quinones, and alkaloids. Fungi of the Chaetomium belong to the large genera of Chaetomiaceae family with more than 350 species, which have been reported as a prolific source of diversiform natural products, such as azaphilones, terpenoids, steroids, chaetoglobosins, xanthones, etc. Cytochalasans are a class of fungal alkaloids composed of a highly substituted perhydro-isoindolone moiety incorporating a macrocyclic ring (either a carbocycle, a lactone or a cyclic carbonate) that are assembled by polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) [4]. Variations in types of amino acids and the substitution patterns of the macrocycle
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