Abstract: Four quinone natural products,endocrocin (1),laccaic acid D (2) and sarubicins A and B (3 and 4),were isolated from the soil-derived actinomycete Streptomyces sp. KIB-H91.Their structures were elucidated on the basis of spectroscopic evidence and comparison with literature reports.Among them,the 13C NMR and HMBC data of compound 4 was reported for the first time in this paper.Sarubicins A and B were the main antimicrobial components with MIC values of 25 μg/mL for 3 against Escherichia coli ATCC 8099 and of 12.5 μg/mL for 4 against Bacillus subtilis ATCC 6633.

Key words: Streptomyces, secondary metabolites, antibiotics, quinones