LAUSR

Marine natural products have proven to be rich sources of structurally novel and biologically active compounds that have become significant chemical entities for drug discovery [1, 2]. To date, there are seven marine natural products and 13 marine-natural-products-inspired compounds that are FDA-approved agents or in clinical trial [3]. Microorganisms derived from the marine environment play an important role in the discovery and development of marine drugs used to treat various diseases [4, 5]. As part of our ongoing investigation of marine bioactive compounds from the coral-derived fungus [6–8], six known compounds of diphenyl derivatives (1–6) were isolated for the first time from the soft coral Sinularia sp. derived fungus Aspergillus sp. collected from the South China Sea. Herein, we report the isolation, structure elucidation, and biological activity of these compounds (1–6). The structures of compounds 1–6 were determined as methyl chloroasterrate (1) [9], methyl dichloroasterrate (2) [9], methyl 3-chloroasterric acid (3) [11], asterric acid (4) [9–11], 2,4-dichloroasterric acid (5) [10, 11], and geodin (6) [9, 12, 15] on the basis of spectroscopic analysis, ESI-MS spectra, and by comparison with those previously reported in the literature. Compound 6 was evaluated for cytotoxic activity against six human cancer cell lines, including breast cancer cell BT474, large cell lung cancer cell NCI-H460, non-small cell lung cancer cell H-1975, chronic myelogenous leukemia cell K562, prostate cancer cell DU145, and lung cancer cell A549. It showed significant cytotoxic activity against all tested cancer cell lines with IC50 values of 8.88, 9.22, 9.96, 11.14, 14.44, and 11.05 M, respectively (Table 1). Staurosporine was used as a positive control [13]. Furthermore, five pathogenic bacterial strains, Staphyloccocus aureus (ATCC 25923), Pseudomonas aeruginosa (ATCC 9027), Escherichia coli (ATCC 35401), Vibrio parahemolyticus (ATCC 17802), and Vibrio anguillarum (ATCC 19019), were also used to test the antibacterial activity of compounds 1–6 [14]. Ciprofloxacin was used as positive control. However, only 5 showed selectively inhibitory activity towards S. aureus with the MIC value of 12.5 M (Table 2).