Search Results (36)

Strophanthus sarmentosus is recognised for various ethnomedicinal applications, including treatment after snakebites. However, only limited scientific evidence exists on its antivenomous capabilities. This study investigates the efficacy of methanol and ethylacetate extracts from S. sarmentosus leaves and roots against Echis ocellatus venom. A non-toxic range for the extracts was determined in rats, and assays were performed to test their anti-hemorrhagic and anti-hemolytic activity as well as their influence on venom-induced blood clotting. In all of these experiments, the extracts demonstrated significant positive effects equal to or better than antivenom. Moreover, the extracts strongly inhibited and even abolished the digestion of the vasoactive neuropeptide bradykinin by snake venom metalloproteinases. Strophantus plants are known for their high content of cardiac glycosides, one of which is the commercially available ouabain, that by itself also considerably inhibited venom-induced bradykinin cleavage. Although ouabain is only present in low amounts in S. sarmentosus when compared to other cardenolides of similar structure, it can be hypothesized that members of this substance class may also have inhibitory properties against venom proteases. S. sarmentosus additionally contains bioactive substances such as flavonoids, terpenoids, tannins, saponins, and alkaloids, which contribute to its protective effects. The study provides scientific data to explain the success of the traditional use of S. sarmentosus plant extracts as a first aid against envenomation in rural Africa. Full article

Male contraception remains an unmet need. Na,K-ATPase α4 (NKA α4), a specific Na⁺/K⁺ transporter of the sperm flagellum, is an attractive target for male contraception. NKA α4 is critical for sperm motility and fertility, and its deletion in male mice causes complete infertility. Our previous structure–activity relationship (SAR) studies on a cardenolide scaffold identified a highly selective, safe NKAα4 inhibitor, but its complex, heavily hydroxylated structure posed challenges for modification and optimization. To address this, we employed a structural simplification strategy to synthesize novel steroidal and non-steroidal analogs and examined their effects on NKAα4 inhibition and sperm motility. Both series reduced sperm motility (up to ~50%), with IC₅₀ values in the picomolar range. Compounds 13 and 45 displayed specificities for NKAα4 over NKAα1, did not affect sperm viability, and showed no reversibility in vitro. Notably, 45, featuring a hexahydronaphthalene core and a benzyltriazole moiety at C5, exhibited potent, highly selective NKAα4 inhibition, reduced sperm motility in vitro and in vivo, and blocked fertilization in vitro. This highlights 45 as a promising lead for non-hormonal male contraception and indicates that the newly generated series of compounds possess the key characteristics needed for further development as potential non-hormonal male contraceptive agents. Full article

Acospectoside A (1) and acovenoside B (2), two cytotoxic cardenolides extracted from the venomous South African bush Acokanthera oppositifolia, are distinguished by their unique structural motifs of the l-acovenose moiety at C-3 and a 1β-O-acetylated cardenolide aglycone. Here, we report the synthesis of these cardiac glycosides featuring delicate introductions of the 1-O-acetyl group under acid-catalyzed conditions, 14β-OH by Mukaiyama hydration, and a C17-butenolide moiety by Stille coupling. Full article

Enzymes capable of processing a variety of compounds enable plants to adapt to diverse environmental conditions. PRISEs (progesterone-5β-reductase/iridoid synthase-like enzymes), examples of such substrate-promiscuous enzymes, are involved in iridoid and cardenolide pathways and demonstrate notable substrate promiscuity by reducing the activated C=C double bonds of plant-borne and exogenous 1,4-enones. In this study, we identified PRISE genes in Plantago media (PmdP5βR1) and Plantago lanceolata (PlP5βR1), and the corresponding enzymes were determined to share a sequence identity of 95%. Despite the high sequence identity, recombinant expressed PmdP5βR1 was 70 times more efficient than PlP5βR1 for converting progesterone. In order to investigate the underlying reasons for this significant discrepancy, we focused on specific residues located near the substrate-binding pocket and adjacent to the conserved phenylalanine “clamp”. This clamp describes two phenylalanines influencing substrate preferences by facilitating the binding of smaller substrates, such as 2-cyclohexen-1-one, while hindering larger ones, such as progesterone. Using structural analysis based on templates PDB ID: 5MLH and 6GSD from PRISE of Plantago major, along with in silico docking, we identified positions 156 and 346 as hot spots. In PlP5βR1 amino acid residues, A156 and F346 seem to be responsible for the diminished ability to reduce progesterone. Moreover, the double mutant PlP5βR_F156L_A346L, which contains the corresponding amino acids from PmdP5βR1, showed a 15-fold increase in progesterone 5β-reduction. Notably, this modification did not significantly alter the enzyme’s ability to convert other substrates, such as 8-oxogeranial, 2-cyclohexen-1-one, and methyl vinyl ketone. Hence, a rational enzyme design by reducing the number of hotspots selectively, specifically improved the substrate preference of PlP5βR1 for progesterone. Full article

ATP-binding cassette (ABC) transporters, particularly those of subfamily B, are involved in cell detoxification, multidrug resistance, drug treatment pharmacodynamics, and also ecological adaptation. In this regard, ABCB transporters may play a decisive role in the co-evolution between plants and herbivores. Cardenolides, toxic steroid glycosides, are secondary plant metabolites that defend plants against herbivores by targeting their sodium–potassium ATPase. Despite their toxicity, several herbivorous insects such as the large milkweed bug (Oncopeltus fasciatus) have evolved adaptations to tolerate cardenolides and sequester them for their own defense. We investigate the role of two ABCB transporters of O. fasciatus for the paracellular transport of cardenolides by docking simulations and ATPase assays. Cardenolide binding of OfABCB1 and OfABCB2 is predicted by docking simulations and calculated binding energies are compared with substrate specificities determined in ATPase assays. Both tested ABCB transporters showed activity upon exposure to cardenolides and Km values that agreed well with the predictions of our docking simulations. We conclude that docking simulations can help identify transporter binding regions and predict substrate specificity, as well as provide deeper insights into the structural basis of ABC transporter function. Full article

Thevetia thevetioides is a species within the Apocynaceae family known for containing cardenolide-glycosides, commonly referred to as cardiac glycosides, which are characteristic of this genus. The seeds of the Thevetia species are frequently used as a model source for studying cardiac steroids, as these glycosides can be more readily extracted from the oil-rich seeds than from the plant’s green tissues. In this work, the cardenolide profile of ripe and immature seeds was determined and compared to establish the main differences. Ripe seeds contain six related cardenolides and triosides, with thevetin B being the predominant component. In contrast, immature seeds exhibit a total of thirteen cardiac glycosides, including monoglycosides such as neriifolin and peruvosides A, B, and C, as well as diglycosides like thevebiosides A, B, and C. Some of these compounds have previously been identified as degradation products of more complex cardiac glycosides; however, their presence in immature seeds, as described in this study, suggests that they may serve as biosynthetic precursors to the triosides observed in mature seeds. The glycoside patterns observed via HPTLC are associated with specific chemical structures characteristic of this genus, typically featuring thevetose or acetyl-thevetose at the first position, followed by glucose or gentibiose in di- or trisaccharides, independent of the trioside aglycones identified: digitoxigenin, cannogenin, or yccotligenin. Ripe seeds predominantly contain triosides, including thevetin B, C, and A, the latter of which has not been previously reported. Full article

The genus Strophantus belongs to the Apocynaceae family of flowering plants which grows primarily in tropical Africa. The plants are widely used in traditional herbal medicine. S. sarmentosus, in particular, is used for the treatment of, e.g., joint pain and rheumatoid arthritis, wound infections, head lice, diarrhea, snake bite, and eye conditions. Despite its widespread use, dedicated research characterizing its bioactive plant components is scarce. Investigations have focused mainly on its cardenolides because of their cardioactivity and historical use as cardiotonic. There are also studies concerning the antibacterial, antioxidant, and anti-inflammatory activity of plant extracts. This review summarizes the present knowledge surrounding the biochemical and analytical research on Strophantus, in general, and S. sarmentosus, in particular, and describes the current state of the field based on the available scientific literature. Full article

Plants in the genus Erysimum produce both glucosinolates and cardenolides as a defense mechanism against herbivory. Two natural isolates of Erysimum cheiranthoides (wormseed wallflower) differed in their glucosinolate content, cardenolide content, and their resistance to Myzus persicae (green peach aphid), a broad generalist herbivore. Both classes of defensive metabolites were produced constitutively and were not further induced by aphid feeding. To investigate the relative importance of glucosinolates and cardenolides in E. cheiranthoides defense, we generated an improved genome assembly, genetic map, and segregating F2 population. The genotypic and phenotypic analysis of the F2 plants identified quantitative trait loci, which affected glucosinolates and cardenolides, but not the aphid resistance. The abundance of most glucosinolates and cardenolides was positively correlated in the F2 population, indicating that similar processes regulate their biosynthesis and accumulation. Aphid reproduction was positively correlated with glucosinolate content. Although the overall cardenolide content had little effect on aphid growth and survival, there was a negative correlation between aphid reproduction and helveticoside abundance. However, this variation in defensive metabolites could not explain the differences in aphid growth on the two parental lines, suggesting that processes other than the abundance of glucosinolates and cardenolides have a predominant effect on aphid resistance in E. cheiranthoides. Full article

The enzymatic acetylation in the organic solvents of a number of the important bioactive cardiac glycosides was investigated. With the bufanolide proscillaridin A and the cardenolide lanatoside C, acylation, as expected, occurred at the secondary 4′-OH of the rhamnopyranosyl unit of the former (by the action of Novozym 435 lipase) and the primary 6′′′′-OH of the terminal glucopyranosyl unit of the latter (best results obtained by the action of the lipase PS). Only lipase PS was found to be able to acylate the cardenolides digitoxin and digoxin at the 4‴-OH of their terminal digitoxose unit. The corresponding monoacetyl derivatives, both of which are commercialized drugs, could be isolated with good yields. The investigation of the Novozym 435-catalyzed acetylation of free D-digitoxose provided a possible explanation for the inability of this lipase to acylate digitoxin and digoxin. Full article

Cancer drug resistance remains a major obstacle in clinical oncology. As most anticancer drugs are of natural origin, we investigated the anticancer potential of a standardized cold-water leaf extract from Nerium oleander L., termed Breastin. The phytochemical characterization by nuclear magnetic resonance spectroscopy (NMR) and low- and high-resolution mass spectrometry revealed several monoglycosidic cardenolides as major constituents (adynerin, neritaloside, odoroside A, odoroside H, oleandrin, and vanderoside). Breastin inhibited the growth of 14 cell lines from hematopoietic tumors and 5 of 6 carcinomas. Remarkably, the cellular responsiveness of odoroside H and neritaloside was not correlated with all other classical drug resistance mechanisms, i.e., ATP-binding cassette transporters (ABCB1, ABCB5, ABCC1, ABCG2), oncogenes (EGFR, RAS), tumor suppressors (TP53, WT1), and others (GSTP1, HSP90, proliferation rate), in 59 tumor cell lines of the National Cancer Institute (NCI, USA), indicating that Breastin may indeed bypass drug resistance. COMPARE analyses with 153 anticancer agents in 74 tumor cell lines of the Oncotest panel revealed frequent correlations of Breastin with mitosis-inhibiting drugs. Using tubulin-GFP-transfected U2OS cells and confocal microscopy, it was found that the microtubule-disturbing effect of Breastin was comparable to that of the tubulin-depolymerizing drug paclitaxel. This result was verified by a tubulin polymerization assay in vitro and molecular docking in silico. Proteome profiling of 3171 proteins in the NCI panel revealed protein subsets whose expression significantly correlated with cellular responsiveness to odoroside H and neritaloside, indicating that protein expression profiles can be identified to predict the sensitivity or resistance of tumor cells to Breastin constituents. Breastin moderately inhibited breast cancer xenograft tumors in vivo. Remarkably, in contrast to what was observed with paclitaxel monotherapy, the combination of paclitaxel and Breastin prevented tumor relapse, indicating Breastin’s potential for drug combination regimens. Full article

Cardiac glycosides are a large class of secondary metabolites found in plants. In the genus Asclepias, cardenolides in milkweed plants have an established role in plant–herbivore and predator–prey interactions, based on their ability to inhibit the membrane-bound Na⁺/K⁺-ATPase enzyme. Milkweed seeds are eaten by specialist lygaeid bugs, which are the most cardenolide-tolerant insects known. These insects likely impose natural selection for the repeated derivatisation of cardenolides. A first step in investigating this hypothesis is to conduct a phytochemical profiling of the cardenolides in the seeds. Here, we report the concentrations of 10 purified cardenolides from the seeds of Asclepias curassavica. We report the structures of new compounds: 3-O-β-allopyranosyl coroglaucigenin (1), 3-[4′-O-β-glucopyranosyl-β-allopyranosyl] coroglaucigenin (2), 3′-O-β-glucopyranosyl-15-β-hydroxycalotropin (3), and 3-O-β-glucopyranosyl-12-β-hydroxyl coroglaucigenin (4), as well as six previously reported cardenolides (5–10). We test the in vitro inhibition of these compounds on the sensitive porcine Na⁺/K⁺-ATPase. The least inhibitory compound was also the most abundant in the seeds—4′-O-β-glucopyranosyl frugoside (5). Gofruside (9) was the most inhibitory. We found no direct correlation between the number of glycosides/sugar moieties in a cardenolide and its inhibitory effect. Our results enhance the literature on cardenolide diversity and concentration among tissues eaten by insects and provide an opportunity to uncover potential evolutionary relationships between tissue-specific defense expression and insect adaptations in plant–herbivore interactions. Full article

Elaeodendron is a genus of tiny trees, shrubs, vines, and herbs consisting of about 23 species. It is used in traditional medicine and has a wide range of pharmacological activities. From the plants in this genus, flavonoids, terpenoids, cardiac glycosides, and cardenolides have been isolated. Elaeodendron species have been the subject of numerous in vitro investigations; however, not many vivo studies are available. Preclinical investigations have also revealed antiviral, anti-HIV, anticancer, antiproliferative, antioxidant, antifungal, anti-inflammation, cytotoxic, anti-plasmodial, anti-arthritic, antibacterial, and anti-diabetic activities. Bioactive substances found in Elaedendron that function in a variety of ways are related to these biological processes. Several databases, including PubMed, Scopus, etc., were searched using keywords such as “Elaeodendron”, “chemical constituents”, “anti-cancer”, “anti-viral”, “pharmacology”, etc., to perform a comprehensive review of the current literature. In this sense, this review intends to provide the most recent developments in the ethnomedical use of Elaeodendron species, and their therapeutic benefits and bioactive compounds. Many species of this genus are reported to be toxic. To provide stronger scientific support for their conventional usage, more in vivo and clinical research for mechanism-based pharmacological evaluation as well as toxicological studies should be carried out in the future. Full article

The present study aims to continue the study of corchorusoside C (1), a cardenolide isolated from Streptocaulon juventas, as a potential anticancer agent. A mechanistic study was pursued in a zebrafish model and in DU-145 prostate cancer cells to investigate the selectivity of 1 towards NF-κB and PARP-1 pathway elements. Compound 1 was found to inhibit the expression of IKKα and NF-κB p65 in TNF-α induced zebrafish and inhibit the expression of NIK in vitro. The protein expression levels of XRCC-1 were increased and p53 decreased in DU-145 cells. XIAP protein expression was initially decreased after treatment with 1, followed by an increase in expression at doses higher than the IC₅₀ value. The activity of caspase-1 and the protein expression levels of IL-18 were both decreased following treatment of 1. The binding interactions for 1 to NIK, XRCC-1, p53, XIAP, and caspase-1 proteins were explored in molecular docking studies. Additionally, the toxicity profile of 1 in zebrafish was favorable in comparison to its analog digoxin and other anticancer drugs at the same MTD in zebrafish. Overall, 1 targets the noncanconical NF-κB pathway in vivo and in vitro, and is well tolerated in zebrafish supporting its potential in the treatment of prostate cancer. Full article

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. Full article

Pergularia tomentosa L., a milkweed tropical plant belonging to the family Asclepiadaceae, is a rich source of unusual cardiac glycosides, characterised by transfused A/B rings and a sugar moiety linked by a double link, generating a dioxanoid structure. In the present report, five cardenolides isolated from the aerial parts of the plant (calactin, calotropin, 12β-hydroxycalactin, 12β,6′-dihydroxycalotropin, and 16α-hydroxycalotropin) were investigated for their biological effects on a human hepatocarcinoma cell line. Cell viability was monitored by an MTT assay. The occurrence of apoptosis was evaluated by detecting caspase-3 activation and chromatin fragmentation. The ability of these compounds to induce autophagy was analysed by monitoring two markers of the autophagic process, LC3 and p62. Our results indicated that all cardenolides had cytotoxic effects, with IC₅₀ ranging from 0.127 to 6.285 μM. All compounds were able to induce apoptosis and autophagy, calactin being the most active one. Some of them also caused a reduction in cell migration and a partial block of the cell cycle into the S-phase. The present study suggests that selected cardenolides from aerial parts of P. tomentosa, particularly calactin, possess potentially desirable properties for further investigation as anticancer agents. Full article