Amethysione and amethysamide, new metabolites from Streptosporangium amethystogenes BCC 27081

Cyclic enaminones and a 4-quinazolinone from an unidentified actinomycete of the family Micromonosporaceae

Four novel cyclic enaminones, designated RD4123A-D (1-4), and a new 4-quinazolinone metabolite, RD4123E (5), were isolated from the culture extract of an unidentified actinomycete strain RD004123, which belongs to the family Micromonosporaceae. Structures of 1-5 were determined by spectroscopic analyses using NMR, MS, and electronic circular dichroism (ECD), combined with quantum chemical calculations of ECD and NMR chemical shifts and biosynthetic consideration. Compounds 1-5 showed weak to modest cytotoxicity against murine leukemia P388 cells, while being inactive against bacteria and fungi.

The secondary metabolites of rare actinomycetes: chemistry and bioactivity

Actinomycetes are outstanding and fascinating sources of potent bioactive compounds, particularly antibiotics. In recent years, rare actinomycetes have had an increasingly important position in the discovery of antibacterial compounds, especially Micromonospora, Actinomadura and Amycolatopsis. Focusing on the period from 2008 to 2018, we herein summarize the structures and bioactivities of secondary metabolites from rare actinomycetes, involving 21 genera.