Determining Antioxidant Activity of Cannabis Leaves Extracts from Different Varieties—Unveiling Nature’s Treasure Trove

Cannabis leaves contain a diverse range of antioxidants, including cannabinoids, flavonoids, and phenolic compounds, which offer significant health benefits. Utilising cannabis leaves as a source of antioxidants presents a cost-effective approach because they are typically discarded during the cultivation of cannabis plants for their seeds or fibres. Therefore, this presented study aimed to assess the antioxidant activity of the leaves of selected hemp cultivars, such as Białobrzeska, Tygra, and Henola, based on the results obtained with the 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid, ferric reducing antioxidant power, cupric reducing antioxidant capacity, and 2,2-Diphenyl-1-picrylhydrazyl assays. The cannabinoid profile was analysed for the antioxidant activity to the contents of cannabidiol (CBD), cannabigerol (CBG), Δ⁹-tetrahydrocannabinol (Δ⁹-THC), and cannabichromene (CBC), determined based on chromatographic assays. The following variables were tested: the impact of various extractants (methanol, ethanol, and isopropanol), and their mixtures (50:50, v/v, as well as extraction methods (maceration and ultra-sound-assisted extraction) significant in obtaining hemp extracts characterised by different cannabinoid profiles. The results revealed that the selection of extractant and extraction conditions significantly influenced the active compounds’ extraction efficiency and antioxidant activity. Among the tested conditions, ultrasound-assisted extraction using methanol yielded the highest cannabinoid profile: CBD = 184.51 ± 5.61; CBG = 6.10 ± 0.21; Δ9-THC = 0.51 ± 0.01; and CBC = 0.71 ± 0.01 μg/g antioxidant potential in Białobrzeska leaf extracts.