Quantitative structure-activity relationships of cardiotonic agents

Chemistry and the Potential Antiviral, Anticancer, and Anti-Inflammatory Activities of Cardiotonic Steroids Derived from Toads

Cardiotonic steroids (CTS) were first documented by ancient Egyptians more than 3000 years ago. Cardiotonic steroids are a group of steroid hormones that circulate in the blood of amphibians and toads and can also be extracted from natural products such as plants, herbs, and marines. It is well known that cardiotonic steroids reveal effects against congestive heart failure and atrial fibrillation; therefore, the term "cardiotonic" has been coined. Cardiotonic steroids are divided into two distinct groups: cardenolides (plant-derived) and bufadienolides (mainly of animal origin). Cardenolides have an unsaturated five-membered lactone ring attached to the steroid nucleus at position 17; bufadienolides have a doubly unsaturated six-membered lactone ring. Cancer is a leading cause of mortality in humans all over the world. In 2040, the global cancer load is expected to be 28.4 million cases, which would be a 47% increase from 2020. Moreover, viruses and inflammations also have a very nebative impact on human health and lead to mortality. In the current review, we focus on the chemistry, antiviral and anti-cancer activities of cardiotonic steroids from the naturally derived (toads) venom to combat these chronic devastating health problems. The databases of different research engines (Google Scholar, PubMed, Science Direct, and Sci-Finder) were screened using different combinations of the following terms: “cardiotonic steroids”, “anti-inflammatory”, “antiviral”, “anticancer”, “toad venom”, “bufadienolides”, and “poison chemical composition”. Various cardiotonic steroids were isolated from diverse toad species and exhibited superior anti-inflammatory, anticancer, and antiviral activities in in vivo and in vitro models such as marinobufagenin, gammabufotalin, resibufogenin, and bufalin. These steroids are especially difficult to identify. However, several compounds and their bioactivities were identified by using different molecular and biotechnological techniques. Biotechnology is a new tool to fully or partially generate upscaled quantities of natural products, which are otherwise only available at trace amounts in organisms.

Antiproliferative activity of cardenolides on cell line A549: structure-activity relationship analysis

Since the beginning, natural products have represented an important source of bioactive molecules for cancer treatment. Among them, cardenolides attract the attention of different research groups due to their cardiotonic and antitumor activity. The observed biological activity is closely related to their Na+/K+-ATPase inhibition potency. Currently, the discovery of new compounds against cancer is an urgent need in modern pharmaceutical research. Thus, the aim of this work is to determine the physicochemical properties and substituent effects that module the antiproliferative activity of cardenolides on the human lung cancer cell line A549. We build and curate a library with results obtained from literature; molecular descriptors were calculated in PaDEL software, and SAR/QSAR analysis was performed. The SAR results showed that cardenolides were sensitive to modifications in C and D steroidal ring and required substituent groups with the function of hydrogen bond acceptor at the C3 position. QSAR models to doubly linked-type cardenolides indicated that properties as lipoaffinity and atoms with the capacity to be hydrogen bond acceptors are involved in the increment of antiproliferative activity on A549 cell line. In contrast, the presence and position of very electro-negative atoms on the molecule decreased the antiproliferative effect on A549 cells. These results suggest that the antiproliferative capacity of cardenolides on the cell line A549 is strongly related to substituent groups on the C3 position, which must not be carbohydrate. Additionally, the steroidal rings C and D must remain without modifications.

Ethnobotany as a pharmacological research tool and recent developments in CNS-active natural products from ethnobotanical sources

The science of ethnobotany is reviewed in light of its multi-disciplinary contributions to natural product research for the development of pharmaceuticals and pharmacological tools. Some of the issues reviewed involve ethical and cultural perspectives of healthcare and medicinal plants. While these are not usually part of the discussion of pharmacology, cultural concerns potentially provide both challenges and insight for field and laboratory researchers. Plant evolutionary issues are also considered as they relate to development of plant chemistry and accessing this through ethnobotanical methods. The discussion includes presentation of a range of CNS-active medicinal plants that have been recently examined in the field, laboratory and/or clinic. Each of these plants is used to illustrate one or more aspects about the valuable roles of ethnobotany in pharmacological research. We conclude with consideration of mutually beneficial future collaborations between field ethnobotanists and pharmacologists.

Identification and characterization of novel sodium/potassium-ATPase inhibitors by virtual screening of a compound database

The medicinal value of cardiac glycoside inhibitors for the treatment of congestive heart failure symptoms stems from their ability to specifically inhibit the ion transport activity of the transmembrane enzyme sodium/potassium-ATPase (Na/K-ATPase) in myocardial cells. In this study, we used the inhibitory potencies of 39 cardiac glycoside analogues for the development of a quantitative structure-activity relationship (QSAR) model for Na/K-ATPase inhibition. In conjunction with a substructure and similarity search, the QSAR model was used to select ten potential inhibitors from a commercial compound database. The inhibitory potencies of these compounds were measured and four were found to be more active than the commonly used inhibitor ouabain. The results of the bioassays were incorporated into a second QSAR model, whose physical interpretation suggested that the nature of substituents in positions 10, 12, and 17 at the cyclopentanoperhydrophenanthrene core of the inhibitors was critical for enzyme inhibition. All descriptors of the QSAR models were conformation-independent, making the search protocol a suitable tool for the rapid virtual screening of large compound databases for novel inhibitors.

Increased ATP content/production in the hypothalamus may be a signal for energy-sensing of satiety: studies of the anorectic mechanism of a plant steroidal glycoside

A steroidal glycoside with anorectic activity in animals, termed P57AS3 (P57), was isolated from Hoodia gordonii and found to have homologies to the steroidal core of cardiac glycosides. Intracerebroventricular (i.c.v.) injections of the purified P57AS3 demonstrated that the compound has a likely central (CNS) mechanism of action. There is no evidence of P57AS3 binding to or altering activity of known receptors or proteins, including Na/K-ATPase, the putative target of cardiac glycosides. The studies demonstrated that the compound increases the content of ATP by 50-150% in hypothalamic neurons. In addition, third ventricle (i.c.v.) administration of P57, which reduces subsequent 24-h food intake by 40-60%, also increases ATP content in hypothalamic slice punches removed at 24 h following the i.c.v. injections. In related studies, in pair fed rats fed a low calorie diet for 4 days, the content of ATP in the hypothalami of control i.c.v. injected animals fell by 30-50%, which was blocked by i.c.v. injections of P57AS3. With growing evidence of metabolic or nutrient-sensing by the hypothalamus, ATP may be a common currency of energy sensing, which in turn may trigger the appropriate neural, endocrine and appetitive responses as similar to other fundamental hypothalamic homeostatic centers for temperature and osmolarity.

A quantitative structure-activity relationship study on a series of Na+, K+-ATPase inhibitors

A quantitative structure-activity relationship (QSAR) study has been made on a new series of digitalis-like Na+,K+-ATPase inhibitors in which the guanylhydrazone group has been replaced by an aminoalkyloxime group. The correlations obtained have shown that the oxime moiety, primary amine group, overall size, and polarizability of the new type of substituents are higly beneficial to the Na+,K+-ATPase inhibition potency of the compounds and that their effect can be quantitatively assessed. The study also showed that the inotropic activity of the compounds is very well correlated with their Na+,K+-ATPase inhibition potency.

Quantitative structure-activity relationships of antianginal drugs

Quantitative structure-activity relationships (QSARs) of various classes of antianginal drugs, e.g. nitrates, beta-adrenergic blocking agents (beta-blockers), and calcium channel blockers (calcium antagonists), have been reviewed. This review gives an overall picture of the mode of action of each class of drugs and points out the specific physicochemical and structural properties that govern their activity. It is observed that in almost all kinds of antianginal drugs the lipophilic factor plays an important role and the next important factor seems to be the steric ones. The electronic factors are found to be occasionally important. In the case of beta-blockers, the most common factor that appeared to govern the activity remained the lipophilicity. In nitrates, too, the activity is observed to primarily depend upon the lipophilicity. In calcium channel blockers, however, the dominant effect is seen to be of steric factors. The steric roles may be essential in drug-receptor interactions, which seem to involve both hydrophobic, and to a lesser extent, electronic interactions.