In the course of our chemical and biological screening program for yet unidentified microbial metabolites, we selected plants of Traditional Chinese Medicine (TCM) as habitats for talented Streptomycetes producer strains for the first time. Liquid pure cultures of strain Streptomyces sp. GS DV232 were found to contain 4-methyl-2-quinazolinamine (1), a potent alkaloid yet unknown from nature. In this study, we investigated the chemical and crystal structure of 1, as well as its antiproliferative bioactivity, and addressed the unusual biosynthesis using feeding experiments.