Isolation, biosynthesis, and biological activity of rubromycins derived from actinomycetes

Natural occurring aromatic polyketides from actinomycetes indicate a structurally and functionally diverse family of polycyclic polyphenols. Some of them are consequently suggested as lead structures for drug development. Among them, rubromycins are derived from a single C26 polyketide chain and exhibit an unusual bisbenzannulated [5,6]-spiroketal system that connects a highly oxygenated naphthazarin motif to an isocoumarin unit. This type of biosynthetically elusive polycyclic polyketides has shown promising pharmacological activities, including antimicrobial, anticancer, and enzyme inhibition activity. The unique structures, intriguing biosynthesis, and marked bioactivities of rubromycins have drawn considerable attention from several chemists and biologists. This review covers the isolation, characterization, biosynthesis, and biological studies of these structurally diverse and complex rubromycins.