Abstract
Three indole derivatives, a novel benzoxazine-indole hybrid (1) and two known indole trimers (2, 3), were isolated from the metagenomic library of the marine sponge Discodermia calyx based on functional screening. Their structures were elucidated by extensive spectroscopic analysis and comparison of their NMR data to that of known compounds. The antibacterial assay indicated that only compound 2 displayed significant antibacterial activity against Bacillus cereus, with approximately 20 mm diameter growth inhibition at 10 µg/paper. HPLC analyses revealed that compound 2 is a newly induced metabolite, and the concentration of 3 was obviously enhanced in contrast to negative control, while 1 was not detected, allowing us to predict that the formation of 2 might be induced by exogenous genes derived from the sponge metagenome, whereas compound 1 could be formed through a non-enzymatic process during the isolation procedure.
Highlights
IntroductionA variety of chemically interesting and biologically significant secondary metabolites have been reported from marine sponges, and most of them have shown significant antibacterial activities [2,3]
Marine sponges and their associated microorganisms have been attracting the attention of chemists and pharmacologists as a very promising potential source of novel bioactive compounds since the discovery of the nucleosides spongothymidine and spongouridine in the marine spongeCryptotethya crypta in the 1950s [1]
Previous investigation of the Discodermia calyx metagenomic library led to the isolation of porphyrins, indole antibiotics, and cyclodipeptides [11,12,13,14,15], indicating that the D. calyx metagenomic library is worthy of further functional screening-based investigation
Summary
A variety of chemically interesting and biologically significant secondary metabolites have been reported from marine sponges, and most of them have shown significant antibacterial activities [2,3]. The marine sponge Discodermia calyx is considered one of most prolific marine producers of novel biologically active compounds, exemplified by the potent antitumor metabolites calyculins [9], and cytotoxic calyxamide cyclic peptides [10], etc. Molecules 2017, 22, 681 insert DNAs derived from the marine sponge D. calyx, was re-screened for antibacterial activity using the two-layer overlay method, resulting in the discovery of one positive clone, designated as pDC115, which produced a clear inhibition zone against Bacillus cereus. Details of the isolation, structural elucidation and antibacterial activities of these compounds are reported
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
