Phenolic Profile, Antioxidant and Anti-Proliferative Activities of Methanolic Extracts from Asclepias linaria Cav. Leaves.

Asclepias linaria Cav. (Apocynaceae) is a shrubby plant endemic of Mexico which has been used in traditional medicine. However, the bioactive potential of this plant remains unexplored. In this study, the phenolic composition, antioxidant, and cytotoxic activities of A. linaria leaves were determined. In order to estimate the phenolic composition of the leaves, the total phenolic, flavonoid, and condensed tannins contents were determined. Furthermore, the antioxidant activity was measured by the scavenging activity of the 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) and 2,2'-azino-bis[3-ethylbenzothiazoline-6-sulphonic acid] (ABTS^•+) radicals and the total antioxidant capacity. The phenolic compounds identified in the A. linaria leaves by ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS) include phenolic acids, such as p-coumaric and ferulic acid, as well as flavonoids, such as rutin and quercetin. The leaves' extracts of A. linaria showed a high scavenging activity of DPPH^• and ABTS^•+ radicals (IC₅₀ 0.12 ± 0.001 and 0.51 ± 0.003 µg/mL, respectively), high total antioxidant capacity values (99.77 ± 4.32 mg of ascorbic acid equivalents/g of dry tissue), and had a cytotoxic effect against K562 and HL60 hematologic neoplasia cells lines, but no toxicity towards the normal mononuclear cell line was observed. These results highlight the potential of A. linaria and could be considered as a possible alternative source of anticancer compounds.