Rediocides A and G as Potential Antitoxins Against Cobra Venom

Trigonostemon species in south China: Insights on its chemical constituents towards pharmacological applications

ETHNOPHARMACOLOGY RELEVANCE

The Euphorbiaceae family, which contains about 300 genera and more than 5000 species, is widely distributed in different regions. Trigonostemon genus comprises a wide group of tropical and temperate plants belonging to the Euphorbiaceae family. This genus includes at least 50 species throughout tropical Asia, extending from India and Sri Lanka to New Guinea. They have been employed by local populations for the treatment of asthma, poisonous snake bites, and food poisoning.

AIM OF THE REVIEW

The main aim of the review is to critically analyze the reported traditional uses, bioactive chemical constituents and pharmacological activities of Trigonostemon species.

MATERIALS AND METHODS

Scientific databases, including Google Scholar, PubMed, CNKI, SpringerLink, Web of Science, Wiley Online Library and SciFinder, were searched using keywords such as "Trigonostemon", "South China", "chemical constituents", or "traditional use". Thus, available articles from 2000 to 2020 were collected and analyzed.

RESULTS AND DISCUSSION

This paper provides systematic data that Trigonostemon species possess a diverse phytochemical composition, (including diterpenes, alkaloids, coumarins, lignins, sesquiterpenes, triterpenoids, flavonoids, and polyphenols) found in different plant organs. Research on Trigonostemon plants has revealed critical therapeutic properties, such as antiviral, anti-tumor, antimicrobial, anti-inflammatory, and insecticidal activities.

CONCLUSIONS

It is envisaged that the current review will add value to more scientific research on Trigonostemon species and enhance/promote the increased interest in the sustainable use of Trigonostemon species as well as lead to the validation of unverified ethnobotanical claims. Future studies on Trigonostemon species would focus on establishing the links between the traditional uses, active compounds and reported pharmacological activities.

Targeting CD155 by rediocide-A overcomes tumour immuno-resistance to natural killer cells

CONTEXT

Therapeutic benefits of immunotherapy are restricted by cancer immune-resistance mechanisms. Rediocide-A (Red-A), a natural product extracted from Traditional Chinese Medicine, is a promising agent to battle against cancer which acts as an immune checkpoint inhibitor.

OBJECTIVE

To investigate the effect of Red-A on NK-cell tumouricidal activity.

MATERIALS AND METHODS

NK cells were co-cultured with A549 or H1299 cells and treated with 10 or 100 nM Red-A for 24 h. Cells treated with 0.1% dimethyl sulphoxide (DMSO) was employed as vehicle control. NK cell-mediated cytotoxicity was detected by biophotonic cytotoxicity and impedance assay. Degranulation, granzyme B, NK cell-tumour cell conjugates and ligands profiling were detected by flow cytometry. Interferon-γ (IFN- γ) production was assessed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Red-A increased NK cell-mediated lysis of A549 cells by 3.58-fold (21.86% vs. 78.27%) and H1299 cells by 1.26-fold (59.18% vs. 74.78%), compared to vehicle control. Granzyme B level was increased by 48.01% (A549 cells) and 53.26% (H1299 cells) after 100 nM Red-A treatment. INF-γ level was increased by 3.23-fold (A549 cells) and 6.77-fold (H1299 cells) after 100 nM Red-A treatment. Red-A treatment down-regulated the expression level of CD155 by 14.41% and 11.66% in A549 cells and H1299 cells, respectively, leading to the blockade of tumour immuno-resistance to NK cells.

CONCLUSIONS

Red-A overcomes immuno-resistance of NSCLCs to NK cells by down-regulating CD155 expression, which shows the possibility of developing checkpoint inhibitors targeting TIGIT/CD155 signalling to overcome immuno-resistance of cancer cells.

Dynamic Docking of Conformationally Constrained Macrocycles: Methods and Applications

Many natural products consist of large and flexible macrocycles that engage their targets via multiple contact points. This combination of contained flexibility and large contact area often allows natural products to bind at target surfaces rather than deep pockets, making them attractive scaffolds for inhibiting protein-protein interactions and other challenging therapeutic targets. The increasing ability to manipulate such compounds either biosynthetically or via semisynthetic modification means that these compounds can now be considered as starting points for medchem campaigns rather than solely as ends. Modern medchem benefits substantially from rational improvements made on the basis of molecular docking. As such, docking methods have been enhanced in recent years to deal with the complicated binding modalities and flexible scaffolds of macrocyclic natural products and natural product-like structures. Here, we comprehensively review methods for treating and docking these large macrocyclic scaffolds and discuss some of the resulting advances in medicinal chemistry.

Protective activity of medicinal plants and their isolated compounds against the toxic effects from the venom of Naja (cobra) species

ETHNOPHARMACOLOGICAL RELEVANCE

Various medicinal plants have protective properties against the toxicities of the venom of cobra snake (Naja species). They may be used as local first aid for the treatment of snakebite victims, and can significantly inhibit lethality, cardio-, neuro-, nephro- and myotoxicity, hemorrhage, and respiratory paralysis induced by the cobra snake venom. The plants or their extracts may also complement the benefits of conventional anti-serum treatment.

AIM OF THE REVIEW

This review provides information on the protective, anti-venom, properties of medicinal plants against snakebites from cobras. In addition, it identifies knowledge gaps and suggests further research opportunities.

METHODS

The literature was searched using databases including Google Scholar, PubMed, ScienceDirect, Scopus and Web of Science. The searches were limited to peer-reviewed journals written in English with the exception of some books and a few articles in foreign languages.

RESULTS

The plants possess neutralization properties against different cobra venom enzymes, such as hyaluronidase, acetylcholinesterase, phospholipase A2 and plasma proteases. Different active constituents that show promising activity against the effects of cobra venom include lupeol acetate, β-sitosterol, stigmasterol, rediocides A and G, quercertin, aristolochic acid, and curcumin, as well as the broad chemical groups of tannins, glycoproteins, and flavones. The medicinal plants can increase snakebite victim survival time, decrease the severity of toxic signs, enhance diaphragm muscle contraction, block antibody attachment to venom, and inhibit protein destruction. In particular, the cardiovascular system is protected, with inhibition of blood pressure decline and depressed atrial contractility and rate, and prevention of damage to heart and vessels. The designs of experimental studies that show benefits, or otherwise, of use of medicinal plants have some limitations: deficiency in identification and isolation of active constituents responsible for therapeutic activity; lack of comparison with reference drugs; and little investigation of the mechanism of anti-venom activity.

CONCLUSION

Despite some current deficiencies in experimental or clinical analysis, medicinal plants with anti-venom characteristics are effective and so are candidates for future therapeutic agents. We suggest that emphasis on identification and testing of active ingredients in research in the future will assist better understanding of their anti-venom activity.

Rediocide A, an Insecticide, induces G-protein-coupled receptor desensitization via activation of conventional protein kinase C

In order to identify small-molecule antagonists of Methuselah (Mth), a Drosophila G-protein-coupled receptor (GPCR) involved in life-span control, a library of natural compounds was screened, and it was found that rediocide A (1), a daphnane ester from the roots of Trigonostemon reidioides and used currently for flea control, potently inhibited calcium mobilization mediated by this receptor. Compound 1 inhibited calcium mobilization in GPCRs other than Mth, indicating that the inhibitory effect was not due to receptor antagonism but rather to a more general mechanism. It was found that 1 can induce GPCR desensitization and internalization, and such effects were mediated by the activation of conventional protein kinase C.