Abstract
Seven new secondary metabolites classified as two perylenequinone derivatives (1 and 2), an altenusin derivative (3), two phthalide racemates (4 and 5), and two phenol derivatives (6 and 7), along with twenty-one known compounds (8–28) were isolated from cultures of the sponge-derived fungus, Alternaria sp. SCSIO41014. The structures and absolute configurations of these new compounds (1–7) were determined by spectroscopic analysis, X-ray single crystal diffraction, chiral-phase HPLC separation, and comparison of ECD spectra to calculations. Altertoxin VII (1) is the first example possessing a novel 4,8-dihydroxy-substituted perylenequinone derivative, while the phenolic hydroxy groups have commonly always substituted at C-4 and C-9. Compound 1 exhibited cytotoxic activities against human erythroleukemia (K562), human gastric carcinoma cells (SGC-7901), and hepatocellular carcinoma cells (BEL-7402) with IC50 values of 26.58 ± 0.80, 8.75 ± 0.13, and 13.11 ± 0.95 μg/mL, respectively. Compound 11 showed selectively cytotoxic activity against K562, with an IC50 value of 19.67 ± 0.19 μg/mL. Compound 25 displayed moderate inhibitory activity against Staphylococcus aureus with an MIC value of 31.25 μg/mL.
Highlights
Perylenequinone derivatives are secondary metabolites characterized by a conjugated aromatic pentacyclic dione, which are mainly derived from fungi [1,2]
HRESIMS data were recorded on a maXis Q-TOF mass spectrometer in a positive ion mode (Bruker, Fällanden, Switzerland). 1D and 2D NMR spectra were measured on an AV 500 MHz NMR
Chemical shifts were given as δ values, with J values reported in Hz
Summary
Perylenequinone derivatives are secondary metabolites characterized by a conjugated aromatic pentacyclic dione, which are mainly derived from fungi [1,2]. Hypocrellins, which are the typical perylenequinone derivatives isolated from fungi Hypocrella bambusae and Shiraia bambusicola, have been studied for their light-induced antitumor and antiviral activities [3]. Many perylenequinone derivatives isolated from Alternaria sp. Showed phytotoxicity, as well as antimicrobial and anticancer activities [4,5,6,7]. Sponge-derived fungi are one of the richest sources of many structurally unique and biologically active secondary metabolites among marine sources [8]. As part of our ongoing research for bioactive natural products from sponge-derived fungi [9,10,11,12,13], the fungus Alternaria sp. Seven new (1–7) and twenty-one known (8–28)
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