Phytochemical, proximate analysis and antioxidant activity of the rhizome of Alpinia nigra (Gaertn.) B.L. Burtt (Zingiberaceae) in Tamulpur district, Assam

Abstract

The present research examines the chemical composition, proximate characteristics and antioxidant analysis of Alpinia nigra’s rhizome extract. Results of GC-MS analysis revealed a total of 22 volatile compounds of which Tris (tert-butyldimethylsilyloxy) arsane (2.89 %), 2-ethylthiolane, S, S-dioxide (3.47 %), Ambrial (6.68 %) and Silicic acid, diethyl bis (trimethylsilyl) ester (4.59 %) were the major compounds. The rhizome was found to have variable quantities of proximate compositions such as moisture content (55.5 %), ash content (4.72 %), crude fat (52 %), crude fibre (41.25 %), crude protein (28.95 µg/g), carbohydrate (46.27 %) and dry matter (33.4 %). The crude extraction of the rhizome was done by Soxhlet apparatus. The phytochemical screening showed the presence of alkaloid, tannin, terpenoid, glycoside, steroid, carbohydrate and a considerable amount of phenol and flavonoid. Phenolic and flavonoid content in the extracts was determined by the Folin-Ciocalteu and aluminium chloride assays as gallic acid equivalent and quercetin equivalent respectively. To evaluate the antioxidant activity of rhizome extract, phosphomolybdenum assay, ferric-reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picryl-hydrazil (DPPH) were used. The findings indicate that the rhizome extract is rich in phenol and flavonoid content and would serve as a promising source of natural antioxidants in the food, cosmetics and pharmaceutical industries.