Phytochemical production and antioxidant activity improvement of <i>Rhinacanthus nasutus</i> (L.) Kurz calli by <i>in vitro</i> polyploidization

Results showed that the callus survival rate decreased with increasing colchicine concentration and exposure time. The highest percentage of induced tetraploid (66.67%) and mixoploid (66.67%) calli were obtained at 0.05% and 0.2% colchicine with exposure times of 48 and 24 h, respectively. Tetraploid calli showed the highest TPC (81.28 mg GAE/g extract), TFC (35.33 mg QE/g extract), and antioxidant activity compared to diploid and mixoploid calli. Additionally, tetraploid calli demonstrated an approximately twofold greater increase in TPC and TFC compared to diploid calli. The analysis of polyploid callus samples revealed that tetraploid calli exhibited the highest antioxidant activity, whereas diploid calli demonstrated the lowest antioxidant activity across all applied assays. Therefore, inducing a tetraploid of <i>R. nasutus</i> calli plays a critical role in modifying phytochemical content and antioxidant activity.