Optimized Extraction of Total Phenolic Compounds from 'Tubtim Siam' Pummelo Peel Using Ultrasonic Technique and Response Surface Methodology

Abstract

The objectives of this research are to optimize extraction condition for total phenolic compounds from 'Tubtim Siam' pummelo peel using ultrasonic assisted extraction and to determine antioxidant activities of the crude extracts. Variables used to study the optimal extraction conditions of total phenolic compounds include concentration of ethanol (10-50 %v/v), extraction time (15-45 min), and ratio of dried pummelo peel: ethanol solution (1:1, 1:2, 1:3). Furthermore, the optimal were determined using a response surface methodology (RSM) by Box Behnken design. The results showed that these three factors affected the yield of extracted total phenolic. Moreover, the statistical analysis provided indications that the data obtained from the experiment should be fitted to polynomial equation because of its high coefficient of determination with R-square = 0.9294. The highest yields of total phenolic compounds were obtained when the samples were dissolved in ethanol at 35%v/v, the extraction time was set at 30 min and the ratio of solid/ethanol was 1:2. Under these optimal conditions, the highest total phenolic compounds yield were 13.67 ± 0.52 mgGAE/gDW from experimental values and 13.66 mgGAE/gDW from predicted values and the scavenging activity of percentage of inhibition by DPPH assay was 32.58 %.