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In the course of screening with the mixed lymphocyte reaction, a new inhibitor of protein kinase C with immunosuppressive activity was isolated from the fermentation broth and mycelia of Streptomyces sp. AB 1869R-359. Although certain similarities exist, this strain is morphologically and physiologically distinct from other reported producers of staurosporine-related compounds. We have found that this strain produces relatively high levels of staurosporine and the new minor compound MLR-52, which possesses the indolo[2,3-a]carbazole chromophore of staurosporine, but differs in the substitution pattern of the sugar moiety. Their structures have been elucidated by mass and NMR spectra. MLR-52 has been shown to inhibit the enzymatic activity of protein kinase C and the murine mixed lymphocyte reaction.

The dunaimycins are a new complex of spiroketal 24-membered macrolides discovered in the fermentation broth of two actinomycetes. Based on taxonomic studies these two cultures, which were isolated from soil, were identified as Streptomyces diastatochromogenes strains AB 1691Q-321 and AB 1711J-452. The dunaimycins possess both immunosuppressive and antimicrobial activity.