Comparison of ohmic heating‐ and microwave‐assisted extraction techniques for avocado leaves valorization: Optimization and impact on the phenolic compounds and bioactivities

Abstract

Avocado tree pruning activities generate a substantial amount of residual biomass, which includes different parts of the plant, such as leaves, twigs, branches, and small fruits. This study aimed to investigate the impact of different green extraction methods of microwave‐assisted extraction (MAE) and ohmic heating‐assisted extraction (OHAE) for the phenolic extraction of avocado leaves based on a statistical approach, central composite design (CCD), and response surface methodology (RSM). Water was preferred using as an environmentally and health‐friendly solvent for both methods. The phenolic composition, antioxidant activity, and antidiabetic potential of the extracts were identified and comparatively assessed. The developed models exhibited a high degree of reliability with optimal conditions for OHAE and MAE, which were determined as 9.38 V/cm voltage gradient, 6 min extraction time, at 60°C, 5 min, and 1 g dried leaf/100 mL water. Epicatechin was identified as the primary phenolic compound in OHAE extracts, while chlorogenic acid was the dominant compound in MAE extracts. The extracts obtained from OHAE and MAE were tested for their ability to inhibit α‐glucosidase activity, with IC50 (mg/mL) values of 0.85 and 1.14, respectively. The DPPH radicals scavenging activity (IC50 mg/L) of OHAE and MAE were detected as 2.96 and 3.41, respectively. In conclusion, both methods yielded extracts rich in polyphenols that displayed high antioxidant activity, but OHAE was found to be superior to MAE in terms of TPC, DPPH, and antidiabetic activities. The results of this study have the potential to make significant contributions toward promoting the principles of a circular economy by facilitating the valorization of the avocado pruning waste.

Hass Avokado Yapraği: Mi̇krodalga Destekli̇ Ekstraksi̇yon Parametreleri̇, Fenoli̇k Bi̇leşi̇kler, Anti̇oksi̇dan Ve Anti̇di̇yabeti̇k Akti̇vi̇teleri̇n Opti̇mi̇zasyonu

“…Extraction of avocado leaves MAE, which is a modern extraction technique and the principle of MAE is based on the polarization of polar water molecules in food by the electric field whereas this vibration of molecules occurs heat which then increases extraction efficiency and decreases extraction time (Gumustepe et al, 2023). In this study, water, a solvent that is environmentally friendly and safe for human health was utilized to extract phenolic compounds.…”