Effects of Different Drying Methods on Bioactive Compound Yield and Antioxidant Capacity of Phyllanthus amarus

Phyllanthus amarus (P. amarus) has been used as a herbal medicine, particularly for liver support, in many countries and its extracts have been shown to possess potent antioxidant and anticancer properties in vitro. The preparation of dried sample is crucial for further extraction and isolation of phytochemicals. In this study, the effects of six different drying methods (hot air, low-temperature air, infrared, microwave, sun, and vacuum drying) on the phytochemical yield and antioxidant capacity were determined to identify the optimal drying method for P. amarus. The results showed that different drying methods, as well as different drying conditions within each method, significantly affected phytochemical yield and antioxidant capacity of P. amarus extracts. Infrared drying at 30°C was the best method for both retention of bioactive compound yield and antioxidant capacity of P. amarus extract, with 12 compounds were identified. In contrast, low-temperature-air drying at 25°C not only required the longest drying time but also significantly reduced the levels of bioactive compounds and antioxidant capacity of P. amarus. Therefore, infrared drying at 30°C is suggested for drying P. amarus for subsequent assessment of bioactivity.