Evaluation of Phytochemical Variations Among the Different Genotypes of Black Turmeric (Curcuma caesia Roxb.)

Black turmeric (Curcuma caesia Roxb.) is widely used in traditional medicine due to its antifungal, antibacterial, anticancer, analgesic, anti-inflammatory, and anticonvulsant properties. Despite these properties, systematic phytochemical evaluation of different genotypes remains limited. This study investigated the biochemical diversity of 21 genotypes collected from different agro-climatic regions of India and cultivated under a randomized block design at two distinct environments- Bhavanisagar and Coimbatore, Tamil Nadu, India. Methanolic extracts of rhizomes were quantitatively assessed for total phenolics, flavonoids, proteins, alkaloids, and cardiac glycosides. The analysis revealed significant variation attributable to both genotypic differences and environmental conditions. At Bhavanisagar, genotype GCA-5 recorded the highest phenolic (3.81 mg GAE/g DW) and cardiac glycoside (183.38 mg SE/g) contents, whereas GMN-10 exhibited the maximum flavonoid concentration (38.29 mg QE/g). The highest protein content was observed in GAN-16 (165.86 mg/100 g DW), while GTE-18 showed the greatest alkaloid accumulation (227.34 mg AE/g). Notably, GTE-18 also ranked among the top performers across most traits at Coimbatore, indicating its strong stability across environments. Correlation analysis revealed a significant positive relationship between cardiac glycosides and phenols (r = 0.49**), proteins (r = 0.40**), and flavonoids (r = 0.34**), as well as between flavonoids and antioxidant capacity (r = 0.59**) and proteins (r = 0.22**), suggesting coordinated biosynthesis. These interrelationships highlight potential metabolic linkages and support the pharmacological synergy of secondary metabolites. Genotypes GCA-5, GTE-18, and GMN-10 demonstrated superior phytochemical accumulation and adaptability across environments, indicating their potential for pharmaceutical and nutraceutical applications.