The concomitant exploitation of two of the green chemistry tools viz., sonication and biocatalysis is reported here for the synthesis of natural alkaloid, tryptanthrin (indolo[2, 1-b]quinazoline-6,12-dione). High intensity ultrasound was applied to facilitate the release of enzymes by disruption of cells of baker's yeast (Saccharomyces cerevisae) as a biocatalyst. The coupled system is an excellent instance to enhance the rate of biocatalyzed reaction and proved to be green alternative to existing methodologies for the synthesis of tryptanthrins. The present method is bestowed with merits such as mild and clean reaction conditions, operational simplicity, tolerance for a wide variety of substituents, green aspects through the avoidance of toxic metal catalysts and affords highly selective conversion with no byproducts.