The Effect of Different Solvents on the Physicochemical Characteristics, Phenolic Content and Antioxidant Activity of Galak Tua (Stemona curtisii) Leaves

Stemona curtisii or locally known as Galak Tua, is a herbaceous plant from family Stemonaceae used in traditional treatments. This study aims to determine the effect of extraction using different solvents on the physicochemical properties, phenolic content and antioxidant activities of S. curtisii leaves. In the present study, different types (methanol, ethanol and acetone) with various concentrations (50%, 80% and 100%) of solvent were used to extract phenolic compound from leaf sample. To determine physicochemical property, colour analysis of leaf extract S. curtisii showed that the 50% ethanol extract from S. curtisii leaves had the significantly highest value (p<0.05) for colour difference as compared to other extracts. For pH values, extract S. curtisii using three various types and concentrations of solvents as well as the control were acidic in the range of 4.12 to 5.26. The pH value of S. curtisii leaves that extracted by 80% ethanol was significantly higher (p<0.05) than other extraction solvents. The results also proved that the 80% methanol extract had the significantly highest (p<0.05) phenolic content (78.3 +/- 2.3 g GAE/kg) than the others. Besides, extraction using 80% methanol and 80% ethanol showed the significantly highest (p<0.05) antioxidant activities towards DPPH which is 84.05 +/- 0.29%. For ABTS test, S. curtisii leaves extracted with 80% methanol had the highest ABTS values (74.44 +/- 0.12%) compared other solvents. For FRAP test, only the 80% methanol extract exhibited significantly the highest (p<0.05) antioxidant activity (13.4 +/- 0.62%). Thus, 80% methanol was the most appropriate solvent for extraction of S. curtisii leaves as the resulting extract had higher phenolic content and antioxidant activities than others.