Three novel indolosesquiterpenes, xiamycin B (1b), indosespene (2), and sespenine (3), along with the known xiamycin A (1a) were isolated from the culture broth of Streptomyces sp. HKI0595, a bacterial endophyte of the widespread mangrove tree Kandelia candel. Agar diffusion assays revealed moderate to strong antimicrobial activities against several bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis, while no cytotoxicity against human tumor cell lines was observed. Together with the previously reported oridamycin, the endophyte metabolites represent the first indolosesquiterpenes isolated from prokaryotes.

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In‐built diversification: Four ansa macrolides, divergolides A–D (1–4), with intriguing structures were isolated from a bacterial endophyte of the mangrove tree Bruguiera gymnorrhiza. These compounds are generated by a common biogenesis from a linear precursor that undergoes various reactions to give the multicyclic structures. This remarkable plasticity results in metabolites with different antibacterial and cytotoxic properties.

Investigation of the fungal strain Monodictys putredinis isolated from the inner tissue of a marine green alga led to the isolation of four new monomeric xanthones and a benzophenone. All structures were elucidated by extensive spectroscopic measurements. The relative configuration of compound 1 was determined by X-ray crystal structure analysis, while for 2 and 3 configurations were confirmed by NOE experiments. Absolute configurations for compounds 1-3 were deduced by comparing experimental circular dichroism spectroscopic data with those calculated employing quantum-chemical time-dependent density functional theory (TDDFT). The compounds were examined for their cancer chemopreventive potential. Xanthone 2 was shown to inhibit cytochrome P450 1A activity with an IC50 value of 3.0 microM. Compounds 2 and 3 displayed moderate activity as inducers of NAD(P)H:quinone reductase (QR) in cultured mouse Hepa 1c1c7 cells, with CD values (concentration required to double the specific activity of QR) of 12.0 and 12.8 microM, respectively. Compound 3 showed weak inhibition of aromatase activity.