Determination of total phenol and flavonoid levels and antioxidant activity of methanolic and ethanolic extract zingiber officinale rosc var. rubrum rhizome

Abstract

Extract of Zingiber officinale var. Rubrum for therapy has been widely investigated, including kidney disease, lung disease, and diarrhea. The solvent used for extraction determines the content of the bioactive compounds and the antioxidant level. This study aims to determine total phenols and flavonoids levels, as well as antioxidant activity of the ethanolic and methanolic extract of Zingiber officinale var. Rubrum rhizome. Total phenol level determined using a spectrophotometer at 765 nm, with gallic acid as a standard, while the total flavonoids at 431 nm with quercetin as standard. Antioxidant activity determined by DPPH assay. The strength of antioxidant activity is expressed in IC50 extract values. The results showed total phenol content of Zingiber officinale var rubrum ethanolic extract 155.78 mg GAE/g, while methanolic extract 132.54 mg GAE/g. Total flavonoid content of ethanol fraction 609.66 mg QE/g, methanolic extract 563.10 mg QE/g. Based on DPPH assay, antioxidant activity was robust with IC50 of ethanolic extract 44.06 μg/mL, and IC50 of methanol extract 30.11 μg/mL.