Antioxidant and cytotoxic potential of n-butanol fraction of Amaranthus viridis

Amaranthus viridis (F. Amaranthaceae), usually known as slender amaranth. It is a multifunctional vegetable that grows in tropical and subtropical areas, sustaining stressful conditions, especially drought, producing a wide array of secondary metabolites: phenolics, terpenes, carotenoids and others, which are responsible for various therapeutic effects. Aerial parts were defatted with hexane, then the defatted residue was extracted in the Soxhlet using 80 % aqueous ethanol. Ethanolic extract was sequentially and repeatedly partitioned with solvents of different polarities: chloroform, ethyl acetate and n-butanol. Then, the n-butanol fraction was hydrolyzed using reflex with 10 % aqueous HCl for 6 hrs. The unhydrolyzed and hydrolyzed n-butanol fractions were subjected to TLC and HPLC. The HPLC analysis was performed using three different eluents; eluent one composed of solvents A ( distilled water with 0.1 % glacial acetic acid) and solvent B ( acetonitrile with 0.1 % glacial acetic acid), eluent two, composed of solvent A (methanol: water: formic acid (10 : 88: 2 v/v)) and solvent B ( methanol: water: formic acid (90: 8: 2 v/v)) and eluent three, consisting of methanol and 0.40 % phosphoric acid (49:51, V/V). According to TLC and HPLC results, the intact n-butanol fraction was evaluated for its antioxidant and cytotoxic effects using DPPH and MTT assays. The study revealed the presence of rutin, hyperoside, quercitrin, apigenin and naringenin only before hydrolysis. While gallic, ferulic, syringic, kaempferol, p. p-coumaric, vanillic, salicylic, protocatechuic acid, myricetin, isorhamnetin, luteolin, vanillin, caffeic acid, chlorogenic acid and quercetin were detected in both unhydrolyzed and hydrolyzed n-butanol fractions. In the DPPH assay, the intact n-butanol fraction showed slightly higher antioxidant activity than the ascorbic acid standard and a mild cytotoxic effect on the HRT-18 cell line with an IC50 equal to 302 µg/mL. In conclusion, prolonged hydrolysis time adversely affects the phenolic compound levels and a mild cytotoxic effect calls for further tests to confirm the anticancer potential.