Keywords: Clinacanthus nutans; Sabah snake grass; Belalai Gajah; drying method; colour; rehydration; antioxidant

Abstract

Proper drying method for natural product is crucial as it determines the physicochemical properties and antioxidant activity of the final product. In this work, drying methods were examined concerning their effect on the colour parameter, rehydration capacity and the antioxidant activity of Clinacanthus nutans leaves. The colour parameter and rehydration capacity were used as physical indicators of the quality of dried C. nutans leaves that were obtained. Three drying conditions were investigated, namely vacuum oven, oven (40-80°C), and air drying. It was found that vacuum oven drying of C. nutans leaves at 60°C resulted in the slightest colour change when compared to fresh sample. Vacuum oven drying method offers lower drying temperature that would be favourable to minimize degradation of thermally unstable bioactive compounds. Meanwhile, the highest rehydration ratio was obtained by oven-dried samples at 80°C followed by vacuum oven drying. Higher rehydration capacity is an indication that fewer damages occurred to the cellular structure of the product during drying. The extraction of C. nutans leaves were performed using supercritical fluid extraction in which air-dried sample obtained the highest antioxidant activity at 41.00 ± 3.07 mg TE/g. The results revealed that different drying methods significantly influenced (p < 0.05) colour parameters, rehydration capacity and antioxidant content of C. nutans leaves. The study also indicated that the colour parameter and rehydration capacity of samples did not represent the bioactive compound content of C. nutans.