Analysis of rhizome colour content, bioactive compound profiling and ex-situ conservation of turmeric genotypes (Curcuma longa L.) from sub-Himalayan terai region of India

Abstract Turmeric (Curcuma longa L.), the golden spice of India, offers a myriad of health benefits primarily due to the presence of polyphenolic curcuminoid pigments. It is believed that the dark orange colour of turmeric rhizome has wide-spread health benefits; but no reliable evidential proof for this is available till date. It is crucial to discern the association of rhizome colour with health benefits. It is also of prime importance to investigate whether the curcuminoids present in the rhizomes are the sole bioactive compounds contributing to its medicinal properties. In the present study, forty five turmeric genotypes were collected from the sub-Himalayan terai region of India which differed in their rhizome colour. Here, the Turmeric Redness Index (TRI) in terms of rhizome colour content (a*/b*) of the genotypes revealed strong correlation with curcuminoid content (+0.93), total phenol content (+0.76), total flavonoids content (+0.82), iron content (+0.55) and antioxidant activity (–0.90 and –0.92 for DPPH and ABTS assays and +0.82 and +0.95 for TAC and CUPRAC assays, respectively, with p