Two new 22-membered macrolides from Streptomyces sp. HU210

Two new 22-membered macrolide metabolites, phthoramycins B (1) and C (2), were isolated from the fermentation broth of Streptomyces sp. HU210. Their structures were elucidated based on extensive spectroscopic techniques including 1D, 2D NMR and HRESIMS data. Compounds 1 and 2 showed moderate cytotoxic activity against human leukemia cell line K562 and lung carcinoma cell line A549.