Antioxidant Capacity of Hemp (Cannabis sativa L.) Leaves and Inflorescences

Plant-derived materials previously regarded as low-value by-products are increasingly investigated as sources of bioactive compounds, yet hemp (Cannabis sativa L.) leaves remain underutilized despite their rich phytochemical profile. This study aimed to evaluate and compare the in vitro antioxidant capacity and total phenolic content of methanolic extracts obtained from the leaves and inflorescences of four hemp cultivars (Finola, Futura 75, Dioica, and Kompolti). Antioxidant capacity (AC) was assessed using ABTS, DPPH, and FRAP assays, while total phenolic content was determined spectrophotometrically. Inflorescences exhibited significantly higher total phenolic content than leaves, with the highest values observed in the Finola cultivar. In contrast, leaf extracts showed greater radical-scavenging capacity in the ABTS and DPPH assays, whereas inflorescences demonstrated higher ferric ion–reducing power in the FRAP assay. Both cultivar and plant part had a significant effect on all evaluated parameters. Overall, hemp leaves and inflorescences displayed distinct and complementary antioxidant profiles in vitro, with Kompolti and Finola leaves characterized by strong radical-scavenging activity and Finola inflorescences showing the highest reducing capacity. These findings provide a comparative characterization of hemp morphological parts with respect to phenolic content and antioxidant behavior, highlighting the potential value of leaves as a source of bioactive compounds.