Introduction of Adonis aestivalis as a new source of effective cytotoxic cardiac glycoside

Probing the interaction of lysozyme with cardiac glycoside digitoxin: experimental and in silico analyses

Digitoxin is a cardiac glycoside used to treat heart failure and heart arrhythmia. However, its therapeutic concentration range is very narrow. High doses of digitoxin are associated with severe side effects; therefore, it is necessary to develop the delivery system which can control the plasma levels of it. In this context, the binding of lysozyme, an important protein having many applications, with digitoxin has been studied to see the ability of the former as a carrier. The studies were carried out using both experimental and computational methods. The intrinsic fluorescence of lysozyme increased on the addition of digitoxin. Fluorescence results suggested that there was a strong interaction between lysozyme and digitoxin which was favored, mainly, by hydrophobic forces. Further, digitoxin affected the secondary structure of lysozyme slightly by causing the partial unfolding of lysozyme. The preferred binding site of digitoxin within lysozyme was the large cavity of the protein. Molecular docking studies also established the principal role of hydrophobic forces in the binding with a significant support of hydrogen bonding. Frontier molecular orbitals of free digitoxin and in complexation with lysozyme were also computed and discussed. The findings from molecular dynamics simulation studies elucidate that, when contrasted with the first and third conformations of the digitoxin-bound lysozyme complex, the second conformation promotes structural stability, reduces flexibility, and enhances the compactness and folding properties of lysozyme. The overall study shows that lysozyme could act as a potential carrier for digitoxin in pharmaceutical formulations.

Cytotoxic effect of carbohydrate derivatives of digitoxigenin involves modulation of plasma membrane Ca2+ -ATPase

Cardiac glycosides, such as digoxin and digitoxin, are compounds that interact with Na⁺ /K⁺ -ATPase to induce anti-neoplastic effects; however, these cardiac glycosides have narrow therapeutic index. Thus, semi-synthetic analogs of digitoxin with modifications in the sugar moiety has been shown to be an interesting approach to obtain more selective and more effective analogs than the parent natural product. Therefore, the aim of this study was to assess the cytotoxic potential of novel digitoxigenin derivatives, digitoxigenin-α-L-rhamno-pyranoside (1) and digitoxigenin-α-L-amiceto-pyranoside (2), in cervical carcinoma cells (HeLa) and human diploid lung fibroblasts (Wi-26-VA4). In addition, we studied the anticancer mechanisms of action of these compounds by comparing its cytotoxic effects with the potential to modulate the activity of three P-type ATPases; Na⁺ /K⁺ -ATPase, sarco/endoplasmic reticulum Ca²⁺ -ATPase (SERCA), and plasma membrane Ca²⁺ -ATPase (PMCA). Briefly, the results showed that compounds 1 and 2 were more cytotoxic and selectivity for HeLa tumor cells than the nontumor cells Wi-26-VA4. While the anticancer cytotoxicity in HeLa cells involves the modulation of Na⁺ /K⁺ -ATPase, PMCA and SERCA, the modulation of these P-type ATPases was completely absent in Wi-26-VA4 cells, which suggest the importance of their role in the cytotoxic effect of compounds 1 and 2 in HeLa cells. Furthermore, the compound 2 inhibited directly erythrocyte ghosts PMCA and both compounds were more cytotoxic than digitoxin in HeLa cells. These results provide a better understanding of the mode of action of the synthetic cardiac glycosides and highlights 1 and 2 as potential anticancer agents.

Two new terpenes from the aerial parts of Clematis chinensis Osbeck

Two new acyclic sesquiterpenoids (1-2) and fourteen known monocyclic monoterpenoids (3-16) were isolated from the aerial parts of Clematis chinensis Osbeck. All compounds were isolated from C. chinensis for the first time. The structures of all compounds were characterized by spectroscopic methods (1 D, 2 D NMR and HRESIMS). In-vitro cytotoxic activity against two human cancer cell lines (MGC-803 and Ishikawa) of all the compounds were evaluated by CCK-8 assay.

Cytotoxic and DNA-Damaging Effects of Aronia melanocarpa, Cornus mas, and Chaenomeles superba Leaf Extracts on the Human Colon Adenocarcinoma Cell Line Caco-2

Aronia melanocarpa, Cornus mas, and Chaenomeles superba leaf extracts contain large amounts of bioactive compounds-mainly polyphenols, which possess many health benefits including anti-cancer properties. Here, we investigate the biological effects of A. melanocarpa, C. mas, and C. superba leaf extracts on the human colon adenocarcinoma cell line Caco-2. The antiproliferative activity of the extracts was measured using the MTT assay. The most cytotoxic extract was C. mas (IC50 = 0.60%). The extracts caused morphological changes in the Caco-2 cells, including partial detachment of cells, necrotic cells, chromatin condensation, cytoplasmic vacuolization, cell nuclei lysis, and nucleus fragmentation. The DNA damage in the Caco-2 cells after exposure to the leaf extracts was measured using the alkaline comet assay. The extracts increased DNA damage in a concentration dependent manner. However, at lower non-cyto- and non-genotoxic (IC0) concentrations the extracts induced DNA repair in Caco-2 cells after exposure to hydrogen peroxide. In conclusion, the results of these studies suggest that A. melanocarpa, C. mas and C. superba leaf extracts can show anticancer activity. However, further research is required on the mechanisms of anti-cancer activity by these extracts, with the application of more advanced and wide-ranging techniques including in vivo experiments.

Digitoxin inhibits HeLa cell growth through the induction of G2/M cell cycle arrest and apoptosis in vitro and in vivo

Cervical cancer is the fourth most common gynecological malignancy affecting the health of women worldwide and the second most common cause of cancer‑related mortality among women in developing regions. Thus, the development of effective chemotherapeutic drugs for the treatment of cervical cancer has become an important issue in the medical field. The application of natural products for the prevention and treatment of various diseases, particularly cancer, has always attracted widespread attention. In the present study, a library of natural products composed of 78 single compounds was screened and it was found that digitoxin exhibited the highest cytotoxicity against HeLa cervical cancer cells with an IC50 value of 28 nM at 48 h. Furthermore, digitoxin exhibited extensive antitumor activities in a variety of malignant cell lines, including the lung cancer cell line, A549, the hepatoma cell line, MHCC97H, and the colon cancer cell line, HCT116. Mechanistically, digitoxin caused DNA double‑stranded breaks (DSBs), inhibited the cell cycle at the G2/M phase via the ataxia telangiectasia mutated serine/threonine kinase (ATM)/ATM and Rad3‑related serine/threonine kinase (ATR)‑checkpoint kinase (CHK1)/checkpoint kinase 2 (CHK2)‑Cdc25C pathway and ultimately triggered mitochondrial apoptosis, which was characterized by the disruption of Bax/Bcl‑2, the release of cytochrome c and the sequential activation of caspases and poly(ADP‑ribose) polymerase (PARP). In addition, the in vivo anticancer effect of digitoxin was confirmed in HeLa cell xenotransplantation models. On the whole, the findings of the present study demonstrate the efficacy of digitoxin against cervical cancer in vivo and elucidate its molecular mechanisms, including DSBs, cell cycle arrest and mitochondrial apoptosis. These results will contribute to the development of digitoxin as a chemotherapeutic agent in the treatment of cervical cancer.