Antioxidant properties from various Ginger species extracts and optimization studies of selected species

Abstract

This work reports a study on evaluation of antioxidant properties from the extract of various ginger species and optimization studies of extraction condition from the selected species. Ginger as one of the most popular tropical herbs in Malaysia has the potential source of natural antioxidant properties replacing over synthetic one, which may lead to side effects. Extraction was done on three ginger species (Zinger officinale, Zingiber spectabile, Zingiber zerumbet) to evaluate their antioxidant activity and total phenolic content. Z. officinale with acetonic extract poses the highest antioxidant activity and phenolic content, which is 79.00±0.0002%, 0.4063±0.0007 mgGAE/g compare to Z. spectabile (65.88±0.0003%,0.3571±0.023 mgGAE/g) and Z. zerumbet (61.52±0.0005%, 0.3257±0.0012 mgGAE/g) followed by methanolic extract, ethyl acetate extract and water. Hence, Z. officinale was chosen to be furthered for screening and optimization studies. Single factor experiment using one factor at a time (OFAT) method was applied to analyze the effect of extraction time (2 to 12 hours), extraction temperature (30 to 80oC) and solid to solvent ratio (1:10 to 1:50 g/mL). Then, the study was preceded with Response Surface Methodology (RSM) coupled with Central Composite Design (CCD) to optimize the extraction conditions on antioxidant activity of Z. officinale which the highest antioxidant activity of 85.49±0.0013 % was obtained at optimum condition of extraction time (8 hours), extraction temperature (60oC) and solid to solvent ratio (1:20 g/mL). Statistical analysis indicated that the extraction temperature seemed to be more significant (p<0.05) parameter affecting antioxidant activity and R2 value of 0.9617 expressed that the model developed was fit and significant in optimizing the extraction conditions of antioxidant properties from ginger species.