Fourteen isomalabaricane triterpenes were isolated from the marine sponge Rhabdastrella globostellata. In addition to the known compounds globostellatic acids A (1) and D (4) and stelliferin riboside (13), 11 of the compounds were new natural products, which included globostelletin (3), eight new globostellatic acid congeners, F to M (2, 5-11), and two new stelliferin ribosides (12 and 14). The isolated compounds were tested against three different cancer cell lines, L5178Y (mouse lymphoma), HeLa (human cervix carcinoma), and PC-12 (rat pheochromocytoma). The isomalabaricane derivatives were found to be selectively active toward the mouse lymphoma cell line L5178Y. The structures were determined by 1D and 2D NMR data and by comparison with spectroscopic data of known related compounds.

Marine sponges are known as a rich source for novel bioactive compounds with valuable pharmacological potential. One of the most predominant sponge genera is Hyrtios, reported to have various species such as Hyrtios erectus, Hyrtios reticulatus, Hyrtios gumminae, Hyrtios communis, and Hyrtios tubulatus and a number of undescribed species. Members of the genus Hyrtios are a rich source of natural products with diverse and valuable biological activities, represented by different chemical classes including alkaloids, sesterterpenes and sesquiterpenes. This review covers the literature until June 2016, providing a complete survey of all compounds isolated from the genus Hyrtios with their corresponding biological activities whenever applicable.

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A new cyclic hexapeptide, nocardiotide A (1), together with three known compounds—tryptophan (2), kynurenic acid (3), and 4-amino-3-methoxy benzoic acid (4)—were isolated and identified from the broth culture of Nocardiopsis sp. UR67 strain associated with the marine sponge Callyspongia sp. from the Red Sea. The structure elucidation of the isolated compounds were determined based on detailed spectroscopic data including 1D and 2D nuclear magnetic resonance (NMR) experimental analyses in combination with high resolution electrospray ionization mass spectrometry (HR-ESI-MS), while the absolute stereochemistry of all amino acids components of nocardiotide A (1) was deduced using Marfey’s method. Additionally, ten known metabolites were dereplicated using HR-ESI-MS analysis. Nocardiotide A (1) displayed significant cytotoxic effects towards the murine CT26 colon carcinoma, human HeLa cervix carcinoma, and human MM.1S multiple myeloma cell lines. The results obtained revealed sponge-associated Nocardiopsis as a substantial source of lead natural products with pronounced pharmacological activities.

Actinomycetes are a relevant source of novel bioactive compounds. One of the pharmaceutically and biotechnologically important genera that attract natural products research is the genus Nocardiopsis, mainly for its ability to produce a wide variety of secondary metabolites accounting for its wide range of biological activities. This review covers the literature from January 2015 until February 2018 making a complete survey of all the compounds that were isolated from the genus Nocardiopsis, their biological activities, and natural sources, whenever applicable.