Subcritical water extraction for selective recovery of phenolic bioactives from kanuka leaves

Kanuka is a good source of functional ingredients like phenolic compounds. This study investigated the selective recovery of antioxidant compounds from kanuka leaves using subcritical water extraction (SWE) at different extraction temperatures (150-210) degrees C, time (0-40)min, and solid-to-solvent ratio, SSR (15-35) g/L. The maximum total phenolic and flavonoid content in the kanuka leaf extracts were (167.93 +/- 2) mg GAE/g dw and (405.4 +/- 8.47) mg QE/g dw, respectively. These amounts were obtained using SWE at 170 degrees C for 20 min with SSR of 15 the extracts also showed the highest antioxidant activity. Eight compounds were identified, including gallic acid, quercetin, and catechin as major compounds. In comparison with conventional ethanol extraction, SWE proved to be a more effective alternative for extraction of bioactive compounds. The results indicate the potential of SWE for the production of high-quality plant extracts from kanuka leaves. (C) 2019 Elsevier B.V. All rights reserved.