Molecular and Chemical Diagnosis of Curcumin Compound and Study its Antioxidant Activity in Two Varieties of Curcuma longa L. Plants

In this work, the Curcumin synthase 1 (CURS1) gene from Curcuma longa L., which plays an important role in the biosynthesis of the curcumin compound, was chosen. The objectives were to identify the genetic variations of CURS1 in two turmeric plant varieties (NDH-98 and GNT-2) and their relationship with curcumin content. Using DNA sequencing technology, the results were analyzed, and the three-dimensional structure of the CURS1 protein was modeled in silico. The primer employed in this investigation amplified 900 bp fragments of the CURS1 gene. A single nucleotide polymorphism (SNP) was identified in the first exon (g.850 C>G), which resulted in a change in the three-dimensional structure of the protein due to the substitution of the amino acid threonine with arginine. Haplotype and nucleotide diversity values were 1.00 and 0.00169, respectively. This investigation involved a relative measurement of the putative CURS1 gene using DNA sequencing from the roots of GNT-2, compared to NDH-98, and an HPLC-assisted curcumin measurement for the two varieties. The amount of curcumin in the rhizomes of GNT-2 was 784.0 µg g-1, while in NDH-98, it was 712.1 µg g-1. The DPPH assay, which evaluates the free radical scavenging capacity of extracts, revealed that the methanolic fraction of Curcuma longa (NDH-98 and GNT-2) demonstrated a significant capacity to inhibit free radicals, with an IC50 value exceeding 125% of the total extract's capacity. Consequently, the methanolic extracts of NDH-98 and GNT-2 exhibited significant effects in the DPPH assay for scavenging free radicals, and regulating vitamin D levels.