Quantification of cardenolide glycosides and antiproliferative activity from a crop of the medicinal plant Asclepias subulata

The development of phytopharmaceuticals for the treatment of diseases such as cancer is a necessity, and its development requires to establish the conditions of commercial cultivation of the plant. Asclepias subulata has exhibited potent antiproliferative activity due to its cardenolide glycoside content. This work aimed to determine the cardenolide profile and antiproliferative activity of ethanolic extracts of A. subulata obtained from an experimental crop under different water stress treatments. Asclepias subulata was germinated in a shade house and was transplanted to the field in spring under different conditions: drought (D), drought with hydrogel (DG), drought with double row (DD), irrigation (I), irrigation with hydrogel (IG), and irrigation with double row (ID). For 12 months, biomass, concentration of calotropin and corotoxigenin 3-O-glucopyranoside, and antiproliferative activity were evaluated. The results showed the lower biomass for D treatments (283 g plant^-1) while the I treatments showed the highest biomass (831 g plant^-1). In general, the concentration of cardenolides was higher under drought treatments: for corotoxigenin 3-O-glucopyranoside, it was 530 μg g^-1 while for calotropin, it was 204 μg g^-1 dry weight. The ethanolic extracts showed strong antiproliferative activity and selectivity in the A549 cell line (human alveolar carcinoma). The D treatment showed an IC₅₀ <2 μg mL^-1 while in ARPE-19 (retinal pigment epithelia cell line), it was IC₅₀ (the half maximal inhibitory concentration)> 200 μg mL^-1. Based on findings in the present work, it can be concluded that A. subulata can be cultivated with a high production of the active compounds. This work represents an important advance in the studies for the potential development of a phytopharmaceutical based on A. subulata.