Tryptanthrin-Based Heterocyclic Scaffolds: Synthesis, Biological Evaluation and Medicinal Chemistry Perspectives

Abstract

Tryptanthrin, chemically identified as indolo[2,1-b]quinazoline-6,12-dione, is a naturally occurring indoloquinazoline alkaloid that has attracted considerable attention because of its structural simplicity, synthetic accessibility and diverse biological activities. The present review provides a concise overview of the chemistry and pharmacological significance of tryptanthrin and its derivatives. Its natural occurrence in medicinal plants and its structural features, including a rigid fused aromatic system and two reactive carbonyl functionalities, make it an attractive scaffold for medicinal chemistry. Various synthetic strategies reported for construction and functionalization of the tryptanthrin nucleus are discussed, ranging from conventional condensation reactions to catalytic, microwave-assisted, photochemical, electrochemical, green, biocatalytic and multicomponent approaches. Particular emphasis is given to structural modification at different positions of the scaffold and the resulting structure–activity relationships. Tryptanthrin and its derivatives exhibit antimicrobial, antifungal, antitubercular, anti-inflammatory, antiprotozoal and anticancer activities. Their anticancer effects have been associated with apoptosis induction, cell-cycle regulation, enzyme inhibition and modulation of important signalling pathways. Recent developments involving spiro derivatives, asymmetric synthesis and metal complexes further demonstrate the versatility of this scaffold. The review also highlights limitations related to solubility, selectivity, pharmacokinetics and in-vivo validation, and identifies future opportunities for developing improved tryptanthrin-based therapeutic agents.