PHENOLIC COMPOUNDS AND ANTIOXIDANT ACTIVITIES OF MACERATED ALPINIA GALANGA STEMS AND LEAVES

Abstract

Alpinia galanga (A. galanga) is a popular culinary ingredient as well as medicinal herb commonly found in Southeast Asia. Compared to the rhizome of A. galanga, the leaves and stems are always being discarded as waste. In this research, active compounds from the stem and leaves of this plant were extracted using maceration technique with ethanol as solvent at a liquid-solid ratio of 20 ml/g. The influence of maceration time and maceration temperature on total phenolic content (TPC) and antioxidant activities of extract were studied using Folin-Ciocalteu assay and DPPH radical scavenging assay, respectively. The maceration time was from 1 to 5 hr and the maceration temperature was examined from 40 ºC to 70 ºC. Crude extract yield for stems and leaves obtained for all parameters of the maceration process was ˃11%. The highest TPC for leaves was obtained at 1 hr (0.038± 0.02 mg GAE/mg DW) and stems at 4 hr (0.024 ± 0.01 mg GAE/mg DW). Similar trend was also observed for antioxidant activity where the highest antioxidant activity obtained for leaves was at 1 hr (IC50=0.136 ± 0.01 mg/ml) and for stems was at 4 hr (IC50=0.320 ± 0.07 mg/ml). Maceration time however, has no significant influence on TPC (p>0.09) and antioxidant activity (p>0.16) of A. galanga. In terms of temperature, the highest TPC was recorded at 70 ºC for both leaves (0.034 ± 0.003 mg GAE/mg DW) and stems (0.019 ± 0.005 mg GAE/mg DW), while the highest antioxidant activity was from sample extracted at 40 ºC for both leaves (IC50 = 0.076 ± 0.05 mg/ml) and stems (IC50 = 0.454 ± 0.16 mg/ml). The best maceration conditions, considering from the antioxidant activity, for both leaves and stems of A. galanga were concluded at 1 hr and 40 ºC in the viewpoint of both extract quality, energy and cost efficiency.