Comparison of Polyphenol Content and Antioxidant Activity in Leaves of Seven Avocado (Persea americana Mill.) Cultivars

Leaves of Persea americana Mill. are a potential source of bioactive compounds; however, current knowledge is limited by the lack of studies that simultaneously evaluate multiple cultivars and leaf developmental stages under comparable field conditions, as well as by inconsistent sampling criteria across studies. This study aimed to assess how leaf developmental stage and cultivar influence phenolic composition and antioxidant activity in avocado leaves grown under field conditions. Total polyphenols, total flavonoids, quercetin-3-O-galactoside, and chlorogenic acid were selected as representative compounds due to their relevance in plant defense and antioxidant capacity. These compounds, together with antioxidant activity, were quantified in young expanding (E1) and fully expanded (E6) leaves of seven avocado cultivars using spectrophotometric methods and HPLC-DAD, and analyzed through two-way ANOVA. Results showed that leaf developmental stage significantly influenced flavonoid content, chlorogenic acid, and antioxidant activity, which were consistently higher in E1 leaves. In contrast, total polyphenol content exhibited cultivar-dependent responses, increasing toward E6 only in specific genotypes, while quercetin-3-O-galactoside remained stable across developmental stages but varied among cultivars. Overall, the results indicate that phenolic metabolism in avocado leaves is regulated by both developmental stage and genotype in a compound-specific manner, with no consistent pattern associated with racial background. From a practical perspective, these findings provide a basis for selecting leaf material according to the intended application: young leaves for higher antioxidant capacity and flavonoid content, and specific cultivars at advanced stages for higher total polyphenol accumulation, supporting the functional valorization of avocado leaves as a source of bioactive compounds.