Four metabolites (1–4), including a new macrolide, O-demethylated-zeaenol (2), and three known compounds, zeaenol (1), adenosine (3), and ergosta-5,7,22-trien-3b-ol (4) were isolated and purified from Curvularia crepinii QTYC-1, a fungus residing in the gut of Pantala flavescens. The structures of isolated compounds were identified on the basis of extensive spectroscopic analysis and by comparison of the corresponding data with those reported in the literature previously. The new compound 2 showed good phytotoxic activity against Echinochloa crusgalli with an IC₅₀ value of less than 5 µg/mL, which was comparable to that of positive 2,4-dichlorophenoxyacetic acid (2,4-D). Compound 1 exhibited moderate herbicidal activity against E. crusgalli with an IC₅₀ value of 28.8 μg/mL. Furthermore, the new metabolite 2 was found to possess moderate antifungal activity against Valsa mali at the concentration of 100 µg/mL, with the inhibition rate of 50%. These results suggest that the new macrolide 2 and the known compound 1 have potential to be used as biocontrol agents in agriculture.

Actinomycete bacteria derived from marine environments are a good source of natural products with diverse biological activities such as cytotoxicity, antiviral, and antimicrobial actions. This review summarizes 191 angucyclines and angucyclinones derived from marine actinomycetes reported in the literature from 2014 to 2023 and introduced the latest developments in actinomycete-silenced biosynthetic gene cluster activation, including heterologous recombination and in situ activation. The key role of redox post-modifications in the biosynthetic process of atypical angucyclines. This review provides insights into the discovery and biosynthesis of valuable angucyclines and angucyclinones from marine-associated actinomycetes and potential lead compounds for the research and development of new drugs.

Six angucyclines including three unreported compounds (1–3) were isolated from Streptomyces sp. XS-16 by overexpressing the native global regulator of SCrp (cyclic AMP receptor). The structures were characterized based on nuclear magnetic resonance (NMR) and spectrometry analysis and assisted by electronic circular dichroism (ECD) calculations. All compounds were tested for their antitumor and antimicrobial activities, and compound 1 showed different inhibitory activities against various tumor cell lines with IC₅₀ values ranging from 0.32 to 5.33 μM.

Heterologous expression has emerged as an effective strategy in activating Streptomyces cryptic gene clusters or improving yield. Eight compounds were successfully obtained by heterologous expression of the type II PKS gene cluster spi derived from marine Streptomyces sp. HDN155000 in the chassis host Streptomyces albus J1074. The structures with absolute configurations were elucidated using extensive MS and NMR spectroscopic methods, as well as theoretical NMR calculations and electronic circular dichroism (ECD) calculations. Interestingly, compound WS009 Z (2) contains a rare thiomethyl group, angumycinone T (4) has a novel oxo-bridge formed between C12a and C4, and angumycinone X (3) showed cytotoxicity toward K562 and NCI-H446/EP cell lines.