SNF4435C and D, novel immunosuppressants produced by a strain of Streptomyces spectabilis. I. Taxonomy, fermentation, isolation and biological activities.

SNF4435C and D, novel nitrophenyl pyrones, have been isolated from the culture broth of an actinomycete strain SNF4435. The strain was identified as Streptomyces spectabilis from its morphological and cultural characteristics. SNF4435C and D showed a potent immunosuppressive activity in vitro and selectively suppressed B-cell proliferation induced by LPS versus T-cell proliferation induced by Con A.