Among the post-harvest processing of medicinal plants, drying is an important and influential process. Given the
numerous applications of medicinal plants, especially Kelussia odoratissima, in the food and pharmaceutical
industries, the aim of this study was to compare the effects of the ultrasound-infrared radiation-vacuum method
with conventional drying methods on the drying time, the total phenolic content (TPC), total flavonoid content
(TFC) and antioxidant activity of K. odoratissima. ANOVA result showed that the effects of drying methods,
drying temperature and their interaction effect on phenolic, flavonoid and antioxidant content were significant
at 1% probability level. In the ultrasound-IR-vacuum method, by increasing temperature from 40 °C to 80 °C, the
TFC increased by 35%. The highest antioxidant capacity was obtained for dry shade treatment, followed by dry
sun treatment and three temperatures, i.e., 40 °C, 60 °C and 80 °C, in the combined method. The proposed optimal
temperatures for the hot air, IR, and ultrasonic drying, were 63 °C, 66 °C and 71 °C, respectivel
