Effect of Drying Methods on the Colour Parameter, Rehydration Capacity and Antioxidant Activity of Clinacan thus nutansLeaves

Proper drying method for natural product is crucial as it determines the physicochemicalproperties and antioxidant activity of the final product. In this work, drying methods wereexamined concerning their effect on the colour parameter, rehydration capacity and theantioxidant activity ofClinacanthus nutansleaves. The colourparameter and rehydrationcapacity were used as physical indicators of the quality of driedC. nutansleaves that wereobtained. Three drying conditions were investigated, namely vacuum oven, oven (40-80C), andair drying. It was found that vacuum oven drying ofC. nutansleaves at 60C resulted in theslightest colour change when compared to fresh sample. Vacuum oven drying method offerslower drying temperature that would be favourable to minimize degradation of thermallyunstable 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 anindication that fewer damages occurred to the cellular structure of the product during drying. Theextraction ofC. nutansleaves 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 resultsrevealed that different drying methods significantly influenced (p < 0.05) colour parameters,rehydration capacity and antioxidant content ofC. nutansleaves. The study also indicated thatthe colour parameter and rehydration capacity of samples did not represent the bioactivecompound content ofC. nutans.