Apoptotic activities of cardenolide glycosides from Asclepias subulata

Inhibition of the CYP Enzymatic System Responsible of Heterocyclic Amines Bioactivation by an Asclepias subulata Extract

Asclepias subulata plant extract has previously demonstrated antiproliferative activity and antimutagenicity against heterocyclic aromatic amines (HAAs) commonly found in cooked meat. The objective of this work was to evaluate the in vitro ability of an ethanolic extract from the medicinal plant Asclepias subulata extract (ASE), non-heated and heated (180 °C), to inhibit the activity of CYP1A1 and CYP1A2, which are largely responsible for HAAs bioactivation. Ethoxyresorufin and methoxyresorufin O-dealkylation assays were performed in rat liver microsomes exposed to ASE (0.002-960 µg/mL). ASE exerted an inhibitory effect in a dose-dependent manner. The half inhibitory concentration (IC₅₀) for unheated ASE was 353.6 µg/mL and 75.9 µg/mL for heated ASE in EROD assay. An IC₄₀ value of 288.4 ± 5.8 µg/mL was calculated for non-heated ASE in MROD assay. However, after heat treatment, the IC₅₀ value was 232.1 ± 7.4 µg/mL. Molecular docking of corotoxigenin-3-O-glucopyranoside, one of the main components of ASE, with CYP1A1/2 structure, was performed. Results show that the interaction of corotoxigenin-3-O-glucopyranoside with CYP1A1/2s' α-helices, which are related with the active site and the heme cofactor, may explain the plant extract's inhibitory properties. Results showed that ASE inhibits CYP1A enzymatic subfamily and may potentially act as a chemopreventive agent by inhibiting bioactivation of promutagenic dietary HAAs.

An updated pharmacological insight into calotropin as a potential therapeutic agent in cancer

Calotropin is a pharmacologically active compound isolated from milkweed plants like Calotropis procera, Calotropis gigantea, and Asclepias currasavica that belong to the Asclepiadaceae family. All of these plants are recognised as medical traditional plants used in Asian countries. Calotropin is identified as a highly potent cardenolide that has a similar chemical structure to cardiac glycosides (such as digoxin and digitoxin). During the last few years, cytotoxic and antitumor effects of cardenolides glycosides have been reported more frequently. Among cardenolides, calotropin is identified as the most promising agent. In this updated and comprehensive review, we aimed to analyze and discuss the specific mechanisms and molecular targets of calotropin in cancer treatment to open new perspectives for the adjuvant treatment of different types of cancer. The effects of calotropin on cancer have been extensively studied in preclinical pharmacological studies in vitro using cancer cell lines and in vivo in experimental animal models that have targeted antitumor mechanisms and anticancer signaling pathways. The analyzed information from the specialized literature was obtained from scientific databases until December 2022, mainly from PubMed/MedLine, Google Scholar, Scopus, Web of Science, and Science Direct databases using specific MeSH search terms. The results of our analysis demonstrate that calotropin can be a potential chemotherapeutic/chemopreventive adjunctive agent in cancer pharmacotherapeutic management.

Antiproliferative activity of standardized herbal phytopreparation from Asclepias subulata

Background: Several studies have shown that active compounds of Asclepias subulata (cardenolides) have antiproliferative effect on human cancer cells. Cardenolides isolated from A. subulata can be used as active chemical markers to elaborate phytopharmaceutical preparations. The aim of this work was to evaluate the antiproliferative effect of a standardized extract of the aerial parts, based on Asclepias subulata cardenolides. Methods: Four standardized extracts were prepared by HPLC-DAD depending on the concentration of calotropin and the antiproliferative activity was measured for the MTT assay, on the A549, MCF-7, HeLa, PC3 and ARPE cell lines. The concentrations of calotropin used for the standardization of the extracts were 10, 7.6, 5 and 1 mg/dL. Results: Standardization of the A. subulata extract based on calotropin at 7.6 mg/g dry weight was achieved and the antiproliferative activity was evaluated over A549, HeLa and MCF-7 cell lines, obtaining proliferation percentages of 3.8 to 13.4%. Conclusions: The standardized extracts of A. subulata at different concentrations of calotropin showed antiproliferative activity against all the cell lines evaluated. The greatest effect was observed against the HeLa cell line.

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 K_i 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 activity of standardized herbal phytopreparation from Asclepias subulata

Background: Several studies have shown that active compounds of Asclepias subulata (cardenolides) have antiproliferative effect on human cancer cells. Cardenolides isolated from A. subulata can be used as active chemical markers to elaborate phytopharmaceutical preparations. To evaluate the antiproliferative effect of a standardized extract of the aerial parts, based on Asclepias subulata cardenolides. Methods: Four standardized extracts were prepared by HPLC-DAD depending on the concentration of calotropin and the antiproliferative activity was measured for the MTT assay, on the A549, MCF-7, HeLa, PC3 and ARPE cell lines. The concentrations of calotropin used for the standardization of the extracts were 10, 7.6, 5 and 1 mg/dL. Results: Standardization of the A. subulata extract based on calotropin at 7.6 mg/g dry weight was achieved and the antiproliferative activity was evaluated over A549, HeLa and MCF-7 cell lines, obtaining proliferation percentages of 3.8 to 13.4%. Conclusions: The standardized extracts of A. subulata at different concentrations of calotropin showed antiproliferative activity against all the cell lines evaluated. The greatest effect was observed against the HeLa cell line.

Calotropis gigantea stem bark extract induced apoptosis related to ROS and ATP production in colon cancer cells

Conventional chemotherapeutic agents for colorectal cancer (CRC) cause systemic side effects and eventually become less efficacious owing to the development of drug resistance in cancer cells. Therefore, new therapeutic regimens have focused on the use of natural products. The anticancer activity of several parts of Calotropis gigantea has been reported; however, the effects of its stem bark extract on inhibition of cancer cell proliferation have not yet been examined. In this study, the anticancer activity of C. gigantea stem bark extract, both alone and in combination with 5-fluorouracil (5-FU), was evaluated. A crude ethanolic extract was prepared from dry, powdered C. gigantea barks using 95% ethanol. This was then partitioned to obtain dichloromethane (CGDCM), ethyl acetate, and water fractions. Quantitative analysis of the constituent secondary metabolites and calotropin was performed. These fractions exhibited cytotoxicity in HCT116 and HT-29 cells, with CGDCM showing the highest potency in both the cell lines. A combination of CGDCM and 5-FU significantly enhanced the cytotoxic effect. Moreover, the resistance of normal fibroblast, HFF-1, cells to this combination demonstrated its safety in normal cells. The combination significantly enhanced apoptosis through the mitochondria-dependent pathway. Additionally, the combination reduced adenosine triphosphate production and increased the production of reactive oxygen species, demonstrating the mechanisms involved in the induction of apoptosis. Our results suggest that CGDCM is a promising anti-cancer agent and may enhance apoptosis induction by 5-FU in the treatment of CRC, while minimizing toxicity toward healthy cells.

LC-DAD-ESI-MS/MS analysis and cytotoxic and antiproliferative effects of chlorogenic acid derivative rich extract from Nerium oleander L. pink flowers

Nerium oleander L. is a widely used medicinal plant for pharmaceutical purposes. In this work, an extract of the pink flowers of this plant (FE) was characterized in terms of phenolic composition by LC-DAD-ESI-MS/MS and bioactivity, namely, antioxidant and antiproliferative effects. A total of 20 compounds from different classes, including derivatives of phenolic acids and flavonoid glycosylated derivatives, were identified in FE. Chlorogenic acid was the dominant phenolic compound in the extract (62.28 ± 1.74 μg mg^-1 of dry extract). The antioxidant activity was assessed by ORAC assay, and FE showed an ability to reduce peroxyl radicals (ORAC value of 791.26 μmol TEAC per g DE). Additionally, the FE inhibited the proliferation of a colorectal cancer cell line (HT29 cells, EC₅₀ = 11.72 ± 0.02 μg mL^-1) and showed no cytotoxicity to confluent Caco-2 cells, a model of human intestinal epithelium. These results provide new information about the phenolic composition of Nerium oleander pink flowers and the bioactivity of the extracts.

Cucurbitacin IIb from Ibervillea sonorae Induces Apoptosis and Cell Cycle Arrest via STAT3 Inhibition

Background:

Cucurbitacin IIb (CIIb) from Ibervillea sonorae has a high capacity to suppress cancer cell proliferation and induce apoptosis. This study investigated the molecular mechanisms related to the antiproliferative and apoptosis induction capacity of CIIb in HeLa cells.

Materials and Methods:

The cell viability and anti-proliferative effect of CIIb were evaluated by using the trypan blue exclusion assay. The effect of CIIb on the mitochondrial membrane potential was determined by flow cytometry using JC-1. The activity of caspase-3 and caspase-9 was evaluated by flow cytometry using commercial kits. The effect of CIIb on the cell cycle was investigated using Fluorescence-Activated Cell Sorting (FACS) analysis. Western blot analysis was used to evaluate both the inhibitory effect of CIIb on the STAT3 signaling pathway and cyclin –B1, and DNA damage by the comet assay.

Results:

CIIb triggers disruption of the mitochondrial membrane potential (Δψm) and consequently activated the caspases -3 and -9, as a result of the activation of the intrinsic pathway of the apoptosis. Likewise, the CIIbinduced cell cycle was arrested in S and G2/M after 24h of treatment. CIIb also reduced the expression of STAT3 and cyclin –B1. Finally, CIIb produced an antiproliferative effect at 48 and 72 h, inducing DNA damage.

Conclusion:

These results demonstrate CIIb-induced apoptosis and cell cycle arrest in HeLa through the inhibition of STAT3.

Caspase-Dependent Apoptosis in Prostate Cancer Cells and Zebrafish by Corchorusoside C from Streptocaulon juventas

Corchorusoside C (1), isolated from Streptocaulon juventas collected in Vietnam, was found to be nontoxic in a zebrafish ( Danio rerio) model and to induce cytotoxicity in several cancer cell lines with notable selective activity against prostate DU-145 cancer cells (IC₅₀ 0.08 μM). Moreover, corchorusoside C induced DU-145 cell shrinkage and cell detachment. In CCD-112CoN colon normal cells, 1 showed significantly reduced cytotoxic activity (IC₅₀ 2.3 μM). A preliminary mechanistic study indicated that 1 inhibits activity and protein expression of NF-κB (p50 and p65), IKK (α and β), and ICAM-1 in DU-145 cells. ROS concentrations increased at 5 h post-treatment, and MTP decreased in a dose-dependent manner. Moreover, decreased protein expression of Bcl-2 and increased expression of PARP-1 was observed. Furthermore, corchorusoside C increased both the activity and protein levels of caspases 3 and 7. Additionally, 1 induced sub-G1 population increase of DU-145 cells and modulated caspases in zebrafish with nondifferential morphological effects. Therefore, corchorusoside C (1) induces apoptosis in DU-145 cells and targets the same pathways both in vitro and in vivo in zebrafish. Thus, the use of zebrafish assays seems worthy of wider application than is currently employed for the evaluation of potential anticancer agents of natural origin.

Chemical composition and cytotoxic screening of Musa cavendish green peels extract: Antiproliferative activity by activation of different cellular death types

Musa cavendish, commonly known as banana, is a fruit with nutritional and therapeutic properties. We investigated the chemical composition and in vitro cytotoxic effect of M. cavendish green peel extract (MHE) on cancer cells for the first time. The compounds characterization was performed by HPLC-UV/Vis and FIA-ESI-IT-MSⁿ. We investigated in vitro cytotoxic effect of Musa cavendish green peels extract (MHE) in HepG2, A-375, MCF-7 and Caco-2 cancer cells. We evaluated the effect of MHE on proliferation of different cell lines through apoptosis, necrosis, mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) content determination. We identified 12 compounds from different classes in the extract, including derivatives of phenolic acids, aglycone flavonoids, glycoside flavonoids and catecholamines. Our results indicate that MHE exerts, after 48 h treatment, an accentuated antiproliferative effect from the dose of 100 μg/mL in all cell lines tested. In HepG2 cells, these effects were related to the induction of cell death, both necrotic and apoptotic, and remarkable changes in cell morphology. Depolarization of MMP and high ROS content were also observed in the cells in a dose-dependent manner. Our results show that MHE may be used as a source of new drugs with anticancer activity.

Cardiac Glycosides in Human Physiology and Disease: Update for Entomologists

Cardiac glycosides, cardenolides and bufadienolides, are elaborated by several plant or animal species to prevent grazing or predation. Entomologists have characterized several insect species that have evolved the ability to sequester these glycosides in their tissues to reduce their palatability and, thus, reduce predation. Cardiac glycosides are known to interact with the sodium- and potassium-activated adenosine triphosphatase, or sodium pump, through a specific receptor-binding site. Over the last couple of decades, and since entomologic studies, it has become clear that mammals synthesize endogenous cardenolides that closely resemble or are identical to compounds of plant origin and those sequestered by insects. The most important of these are ouabain-like compounds. These compounds are essential for the regulation of normal ionic physiology in mammals. Importantly, at physiologic picomolar or nanomolar concentrations, endogenous ouabain, a cardenolide, stimulates the sodium pump, activates second messengers, and may even function as a growth factor. This is in contrast to the pharmacologic or toxic micromolar or milimolar concentrations achieved after consumption of exogenous cardenolides (by consuming medications, plants, or insects), which inhibit the pump and result in either a desired medical outcome, or the toxic consequence of sodium pump inhibition.