The new streptoglutarimides A−J (1−10) and the known streptovitacin A (11) were isolated from a marinederived actinomycete, Streptomyces sp. ZZ741. Structures of the isolated compounds were elucidated based on their HRESIMS data, extensive NMR spectroscopic analyses, ECD calculations, Mosher′s method, and a single-crystal X-ray diffraction experiment. Streptoglutarimide H (8) and streptovitacin A (11) showed potent antiproliferative activity against human glioma U87MG and U251 cells with IC 50 values of 1.5−3.8 μM for 8 and 0.05−0.22 μM for 11. All isolated compounds exhibited antimicrobial activity with MIC values of 9−11 μg/mL against methicillin-resistant Staphylococcus aureus, 8−12 μg/mL against Escherichia coli, and 8−20 μg/mL against Candida albicans.

The new alkaloids marinacarbolines E–Q (1–10, 12–14), caerulomycin N (15), and actinoallonaphthyridine A (16), together with the known marinacarboline C (11) and cyanogramide (17), were isolated from the actinomycete Actinoalloteichus sp. ZZ1866. The structures of the isolated compounds were elucidated based on their HRESIMS data, extensive NMR spectroscopic analyses, Mosher’s method, ECD calculations, single-crystal X-ray diffraction analysis, and chemical degradation studies. Marinacarbolines E–L (1–8) share an indole-pyridone-imidazole tetracyclic skeleton, which is the first example of this kind of skeleton. Caerulomycin N (15) and cyanogramide (17) exhibited cytotoxic activity against both human glioma U251 and U87MG cells with IC50 values of 2.0–7.2 μM. Marinacarbolines E (1), G (3), I (5), and M (9) showed cytotoxic activity against U87MG cells with IC50 values of 2.3–8.9 μM.

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