Secondary Metabolites, Pharmacognostic and Therapeutic Activities of the Rhizome Extract of Curcuma longa Grown in South-West, Nigeria

Abstract

Curcuma longa is an important plant with diverse medicinal properties. The aim of this study was to determine the chemical constituents and phenolic contents, ascorbic acid content, antioxidant, anti-arthritic and antibacterial potential of the rhizome extract of C. longa grown in South-West, Nigeria. GC-MS, UVVisible Spectrophotometer, other established biochemical methods were used to investigate the rhizome extract. The GC-MS analysis revealed the presence of sixty (60) therapeutically active phytochemicals. The most abundant components were: nopol (23.0%), megastigma-3,7(E),9-triene (9.0%), curlone (7.0%) and (4E)-2-methyl-4-octenal (5.9%). The percentage of α-curcume, α-zingiberene and βsesquiphellandrene were 0.9, 1.6 and 1.9%, respectively. The polyphenol, flavonoid and ascorbic acid values were 3,270.30 ±0.00 µgmg-1 GAE, 51.79±0.00 µgmg-1 QE and 51.48±0.03 µgmg-1 AAE, respectively. The rhizome extract of C. longa contained some phenolic compounds such as o-guaiacol (1.5%), p-vinylguaiacol (2.0%) and ferulic acid methyl ester (1.5%). The rhizome extract showed very low IC50 and therefore high AAI with Galvinoxyl (25.0 µgml-1 and 1.68) and DPPH (5.0 µgml-1 and 8.0). The total antioxidant capacity value was 1,173.08±0.00 µgmg-1 AAE. The rhizome extract also gave high anti-arthritic protein denaturation value between 86.82-69.32%. The extract was active against all the tested bacteria isolates showing high zones of inhibition (10.0-24.0 mm). The studies provide important information for efficient and effective uses of rhizome of C. longa for nutritional and therapeutic purposes.