A novel streptonigrin type alkaloid from the Streptomyces flocculus CGMCC 4.1223 mutant Delta stnA/Q2

Streptonigrin (STN) is a highly functionalized aminoquinone alkaloid with broad and potent antitumor activities. Previously, the biosynthetic gene cluster of STN was identified in Streptomyces flocculus CGMCC 4.1223, revealing an alpha/beta-hydrolase (StnA) and a methyltransferase (StnQ2). In this work, a double mutant Delta stnA/Q2 was constructed by genetic manipulation and produced a novel derivative of STN, named as streptonigramide. Structure of streptonigramide was established by spectroscopic analyses. Its biosynthetic pathway has been proposed as well.