Abstract
Ochrazepines A−D (1−4), four new conjugates dimerized from 2-hydroxycircumdatin C (5) and aspyrone (6) by a nucleophilic addition to epoxide, were isolated from the fermentation broth of the coral-associated Aspergillus ochraceus strain LCJ11-102. Their structures including absolute configurations were determined based on spectroscopic analysis and chemical methods. Compounds 1−4 were also obtained by the semisynthesis from a nucleophilic addition of 2-hydroxycircumdatin C (5) to aspyrone (6). New compound 1 exhibited cytotoxic activity against 10 human cancer cell lines while new compounds 2 and 4 selectively inhibited U251 (human glioblastoma cell line) and compound 3 was active against A673 (human rhabdomyoma cell line), U87 (human glioblastoma cell line), and Hep3B (human liver cancer cell line) with IC50 (half maximal inhibitory concentration) values of 2.5–11.3 μM among 26 tested human cancer cell lines.
Highlights
As more and more dimeric compounds were discovered from organisms, dimers have become an important and large part of the natural products (NPs) family [1]
Spectra at m/z 508.1721 (Figure S37) and 508.1711 [M + H]+ (Figure S51), respectively. Examination of their NMR data (Table 1, Figures S38-S41 and S52-S55) showed that they both have the same aspyrone and 2-hydroxycircumdatin C fragments, which could be confirmed by the 2D NMR correlations
The fungus Aspergillus ochraceus LCJ11-102 was isolated from the coral Dichotella gemmacea (Valenciennes) collected in Lingao, Hainan province, China
Summary
As more and more dimeric compounds were discovered from organisms, dimers have become an important and large part of the natural products (NPs) family [1]. The hybrid compounds formed from two different types of NPs have attracted a lot of attention. Coral-associated microorganisms are an important part of our research From this type of organism, we have identified some bioactive metabolites with new structures, such as cottoquinazolines B−D [10], Mar. Drugs 2019, 17, 400; doi:10.3390/md17070400 www.mdpi.com/journal/marinedrugs. Asbioactive part of an ongoing search for bioactive with novel structures from coral-associated fungal strains isolated from 12 coral samples. Da were observed inwith the LC-MS profile of the the culture of in LCJ11-102, larger thanofthose extract of the culture of LCJ11-102, larger than those of known circumdatins.
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