Advances in Antimicrobial Natural Products Derived from Marine Actinomycetes

Objective: This review describes the discovery during the last five years of novel compounds with significant antimicrobial activity from marine actinomycetes; descriptions include their origins, relevant structures and antimicrobial activities. These antimicrobial compounds belong to several structural classes including alkaloids, peptides, polyketides, macrolides, glycosides, phenols and others. They further express antimicrobial activity against Gram-positive, Gram-negative and fungal pathogens. Method: We additionally summarize the present knowledge of marine actinomycetes, as a potential source for producing antibiotics. Significantly, more than 15 kinds of structures, such as xinghaiamine A (12), and arenimycin (82), showed antimicrobial activity against multidrug resistant (MDR) pathogenic strains. Compounds such as mollemycin A (17, IC50 values of 10 - 50 nM) and glycosylated macrolactins (83 and 84, MIC values of 0.055 - 0.220 mu M) showed potent activity and may be considered as candidates with significant potential for antibiotic drug discovery. Three different types of compounds, lajollamycins (8-11), bahamaolides (95 and 96) and glycosylated benzoxazine (102 and 103) showed inhibitory activity against Candida albicans isocitrate lyase (ICL). Conclusion: As compiled in this review, antimicrobial natural products are frequently found in marine actinomycetes and are an important supply of molecules with great potential for biotechnological applications. Marine actinomycetes, therefore, attracted recent research interest. The opportunities and challenges for exploring marine actinomycetes-derived natural products need to be further elucidated.