Phenopyrrolizins A and B, Two Novel Pyrrolizine Alkaloids from Marine-Derived Actinomycetes Micromonospora sp. HU138

Two previously undescribed pyrrolizine alkaloids, named phenopyrrolizins A and B (1 and 2), were obtained from the fermentation broth of marine-derived Micromonospora sp. HU138. Their structures were established by extensive spectroscopic analysis, including 1D and 2D NMR spectra as well as HRESIMS data. The structure of 1 was confirmed by single-crystal diffraction analysis and its racemization mechanism was proposed. The antifungal activity assay showed that 2 could inhibit the mycelial growth of Botrytis cinerea with the inhibitory rates of 18.9% and 35.9% at 20 μg/disc and 40 μg/disc, respectively.

Secondary Metabolites from Marine Micromonospora: Chemistry and Bioactivities

Marine Micromonospora was revealed to be a rather untapped and a rich source of chemically diverse and unique bioactive natural products. This review is aimed to make a comprehensive survey of secondary metabolites that were derived from marine Micromonospora including chemical diversity and biological activities. A total of 116 compounds from 41 marine Micromonospora species have been reported, covering the literatures from 1997 to 2019. These compounds contain several structural classes such as polyketides (PKS), nonribosomal peptides (NRPS), PKS-NRPS hybrids, terpenes and others, and they present cytotoxic, antibacterial, antiparasitic, chemopreventive or antioxidant activities.