Avocado leaves: Influence of drying process, thermal incubation, and storage conditions on preservation of polyphenolic compounds and antioxidant activity

Total phenolic content and antioxidant activity of hydroalcoholic extract of avocado leaves (Persea americana (PA)) were determined by α,α-diphenyl-β-picrylhydrazyl, ^∙NO, O₂^∙–, and ^∙OH radical capture and reducing power test. Liquid chromatography coupled to mass spectrometry/electron spray ionization was used to identify 19 types of polyphenols, as flavan-3-ols and flavonol glycosides, in PA. Stability assays were performed to optimize conditions for preserving antioxidant activity and polyphenols during drying, thermal incubation, and storage of the extract. Extracts, obtained from leaves dried at 70°C or higher, showed lower values for total phenolic content and antioxidant activity. Compared with the values of leaves dried at 60°C or lower, these differences were statistically significant (p ≤ 0.05). Incubating PA in solution, at 40°C–100°C for up to 8 h, did not produce significant changes in total phenolic content or antioxidant activity. No statistically significant changes in the total phenolic content or antioxidant activity (p ≤ 0.05) occurred after storage at 4°C and 25°C for up to 10 months. PA was shown to possess diverse polyphenolic compounds with robust antioxidant activity. Precise control of drying temperature was an important parameter for maintaining high levels of phenolic compounds and antioxidant activity of PA.