Abstract
Bioassay-guided fractionation of the crude extract of fermentation broth of one symbiotic strain Aspergillus sp. D from the coastal plant Edgeworthia chrysantha Lindl. led to isolation of one new meroterpenoid, tricycloalternarene 14b (1), together with four known analogs (2–5), tricycloalternarenes 2b (2), 3a (3), 3b (4), and ACTG-toxin F (5). Their chemical structures were unambiguously established on the basis of NMR, mass spectrometry, and optical rotation data analysis, as well as by comparison with literature data. Biological assays indicated that compound 2 exhibited potent in vitro cytotoxicity against human lung adenocarcinoma A549 cell line with an IC50 value of 2.91 μM, and compound 5 had a moderate inhibitory effect on Candida albicans, with an MIC value of 15.63 μM. The results indicated that this symbiotic strain D is an important producer of tricycloalternarene derivatives, with potential therapeutic application in treatment of cancer and pathogen infection.
Highlights
The fungi of the Aspergillus genus are well known to be a rich source of secondary metabolites with a broad spectrum of biological activities
The chemical structures of compounds 2–5 were assigned as TCAs 2b (2), 3a (3), 3b (4) and ACTG-toxin
It was deduced that the double bond between C-2 and C-3 in 2 was transferred to the position of C-3 and C-4 in 1, while the hydroxyl group at C-1 in 2 was moved to C-2 in 1. This assumption was certified by the observed variation of their 13 C-NMR data, in which the chemical shift values of C-1 (68.7), C-2 (135.2) and C-4 (24.9) in 2 were changed to 29.8, 70.7, 125.2, respectively, in 1 (Table 1)
Summary
The fungi of the Aspergillus genus are well known to be a rich source of secondary metabolites with a broad spectrum of biological activities. Had documented 807 unique non-redundant natural products derived from 675 Aspergillus species by 2017 [1]. A growing amount of evidence indicates that symbiotic Aspergillus strains are an important contributor of bioactive natural products. The differences mainly occur in the isoprenoid side chain and the substitution pattern of the C-ring of TCAs. The differences mainly occur in the isoprenoid side chain and the substitution pattern of the C-ring of TCAs These metabolites are of intense interest to natural drug chemists due to their remarkable antimicrobial and cytotoxic effects. In our ongoing chemical investigation of symbiotic Aspergillus strains for discovery of new bioactive natural products, one new meroterpenoid, named TCA 14b (1), along with four derivatives, TCAs 2b (2), 3a (3), 3b (4), and ACTG-toxin F (5), was isolated from Aspergillus sp.
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