Retention of phytochemical properties and antioxidant potential of Conyza canadensis (L.) under different drying methods

The retention of natural antioxidant potential of medicinal plants has been a key focus in phytopharmacology. However, the antioxidant potential of Conyza canadensis (L.), particularly the influence of different drying methods on phytochemical retention and activity, remains insufficiently understood. Therefore, this study was conducted during the year 2023-24 at Islamic University of Science and Technology, Kashmir and Sher-e-Kashmir university of Agricultural Sciences and Technology of Kashmir, India to evaluate the impact of different drying methods viz., sun-drying (SD), shade-drying (SHD), cabinet-drying (CD), and vacuum-drying (VD) on the drying kinetics, physical quality, phytochemical composition, and antioxidant activity of C. canadensis (L.) leaves collected from Kashmir, India. Drying kinetics were modelled, and the final powders were analysed for moisture content, water activity (aw), and colour. Methanolic extracts were assessed for Total Phenolic Content (TPC), Total Flavonoid Content (TFC), and antioxidant activity (DPPH, ABTS, FRAP). The results demonstrated a significant (p ≤ 0.05) influence of the drying technique. Vacuum drying was the fastest method to reach safe moisture levels ( less than 10%) and best preserved the colour of the leaves. Vacuum-dried leaves exhibited the highest TPC (85.23 mg GAE/g) and TFC (42.15mg QE/g), correlating with superior antioxidant capacity (DPPH: 76.70%; ABTS: 5.29 mg TE/g; FRAP: 0.66 mg FSE/g). Sun-drying resulted in the greatest degradation of phytochemicals and antioxidant activity. These findings provide a comprehensive optimisation strategy for processing C. canadensis, positioning it as a viable source of natural antioxidants for food and pharmaceutical industries.