Calotropin and corotoxigenin 3-O-glucopyranoside from the desert milkweed Asclepias subulata inhibit the Na+/K+-ATPase activity.

Na+/K+-ATPase is an essential transmembrane enzyme found in all mammalian cells with critical functions for cell ion homeostasis. The inhibition of this enzyme by several cardiotonic steroids (CTS) has been associated with the cytotoxic effect on cancer cell lines of phytochemicals such as ouabain and digitoxin. This study evaluated the inhibitory capacity of cardenolides calotropin and corotoxigenin 3-O-glucopyranoside (C3OG) from Asclepias subulata over the Na+/K+-ATPase activity in vitro and silico. The inhibitory assays showed that calotropin and C3OG decreased the Na+/K+-ATPase activity with IC50 values of 0.27 and 0.87 µM, respectively. Furthermore, the molecules presented an uncompetitive inhibition on Na+/K+-ATPase activity, with Ki values of 0.2 µM to calotropin and 0.5 µM to C3OG. Furthermore, the molecular modeling indicated that calotropin and C3OG might interact with the Thr797 and Gln111 residues, considered essential to the interaction with the Na+/K+-ATPase. Besides, these cardenolides can interact with amino acid residues such as Phe783, Leu125, and Ala323, to establish hydrophobic interactions on the binding site. Considering the results, these provide novel evidence about the mechanism of action of cardenolides from A. subulata, proposing that C3OG is a novel cardenolide that deserves further consideration for in vitro cellular antiproliferative assays and in vivo studies as an anticancer molecule.

Antiproliferative and Apoptotic Activities of the Medicinal Plant Ziziphus obtusifolia.

BACKGROUND: Ziziphus obtusifolia is a spiny shrub found in Northwest Mexico desert, with traditional medicinal use to treat several diseases including cancer. OBJECTIVE: The aims of the present study were to evaluate the antiproliferative and apoptotic activities of the aerial parts of this plant. MATERIALS AND METHODS: The methanol extract and its fractions were prepared using several solvents. The antiproliferative activity was evaluated by the (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium) (MTT) assay on HeLa, A549, RAW 264.7, M12.C3.F6, and L-929 cell lines, and the apoptotic activity using Annexin V and (5,50,6,60-tetra-chloro-1,10,3,30-tetra-ethylbenzimidazol-carbocyanine iodide) staining. The most active fraction was further separated by column chromatography. RESULTS: The most active fraction was hexane with an IC50 of 90.4 µg/mL against RAW 264.7, 94 µg/mL against M12.C3.F6, 165.5 µg/mL against HeLa and 187.7 µg/mL against A549 cell lines. In apoptotic activity assays the methanol extract and its n-hexane fraction were found to induce mitochondrial depolarization in HeLa cells (83 and 87% respectively), and both induced the externalization of the phosphatidylserine increasing the percentage of cells in early apoptosis from 1.4% in untreated control cells, to 1.9% and 3.5% for methanol extract and n-hexane fraction-treated cells, respectively, statistically different for the total percentage of apoptotic cells (P < 0.05). CONCLUSIONS: These results show that Z. obtusifolia has antiproliferative and apoptotic activities in vitro and confirms its use in traditional medicine. SUMMARY: The methanol extract and its fractions using several solvents were evaluated in the antiproliferative activity by the MTT assay on HeLa, A549, RAW 264.7, M12.C3.F6, and L-929 cell lines, and the apoptotic activity using Annexin V and (5,50,6,60-tetra-chloro-1,10,3,30-tetra-ethylbenzimidazol-carbocyanine iodide) staining. The most active fraction against cell lines was hexane. In apoptotic activity assays, the methanol extract and its n-hexane fraction were found to induce mitochondrial depolarization. This results we showed that Ziziphus obtusifolia has antiproliferative and apoptotic activities in vitro.Abbreviations Used: DMEM: Dulbecco's modified eagle's medium, DMSO: Dimethyl sulfoxide, MTT: (3-4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium), JC-1: (5,50,6,60-tetra-chloro-1,10,3,30-tetra-ethylbenzimidazol-carbocyanine iodide), FBS: Fetal bovine serum, CAPE: Caffeic acid phenethyl ester, PBS: Phosphate-buffered saline.