Effects of drying temperatures and residual moisture content on marker compounds, total phenolics and antioxidant capacity of Orthosiphon stamineus benth (Misai Kucing) leaves

Abstract

Experiments were conducted to determine effect on total phenolic, biomarker compounds and antioxidant capacity. Different temperature treatment (40, 50 and 70°C) and drying stage for different moisture content (initial, mid and final) were used in order to analyze the effect on misai kucing active constituents. Analyses were conducted on fresh, half-dried and dried leaves. The total phenolic compounds and antioxidant activity were evaluated by using the Folin-Ciocalteu method and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity assay and analyzed by using UV/VIS Spectrophotometer. Rosmarinic and sinensetin acid were determined using High Performance Liquid Chromatography (HPLC). The results of showed significant differences on concentration of total phenolic compounds, rosmarinic and sinensetin acid and free radical scavenging activity when leaves were treated at different temperatures and moisture content. It is observed that the temperature treatment at 40 °C and maximum drying resulted in higher concentration of total phenolic, biomarker compounds and antioxidant capacity. It is also found that concentration of sinensetin acid increased when high temperature used.