Synthesis, antibacterial and antifungal activity of myricetin derivatives containing piperidine and amide fragments

BACKGROUND

Continuous use of synthetic bactericides and fungicides is causing pathogens to develop resistance, resulting in increased use of pesticides and affecting food security. The green pesticides derived from natural products could reduce or avoid 'pesticide hazards' caused by synthetic pesticides as a result of their unique mechanism of action. Therefore, it is of great significance to create green pesticides with novel structures.

RESULTS

Herein, 30 novel myricetin derivatives containing piperidine and amide fragments were designed and synthesized using active group splicing. Among them, compound Z30 had excellent inhibitory effect against Xanthomonas oryzae pv. Oryzae (Xoo) with the half effective concentration (EC50 ) of 2.7 μg mL-1 . Compound Z26 not only exhibited better antibacterial activity against Xaxonopodis pv. Citri (Xac) with EC50 of 3.9 μg mL-1 , but also displayed higher antifungal activity against Rhizoctonia solani (Rs) with EC50 of 8.3 μg mL-1 . In vivo experiments proved that Z30 against bacterial blight of rice and Z26 against rice blast exhibits significant protective and curative effect. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Z26 and Z30 could change the integrity of cell wall and membrane of pathogen Xoo, Xac and Rs, resulting in cytoplasmic leakage and eventually death. Enzymatic assay, molecular docking and molecular dynamics simulations (MDs) indicated that Z26 could be used as a potential succinate dehydrogenase inhibitor (SDHI).

CONCLUSION

Z26 and Z30 significantly reduced the pathogenicity of the pathogens, which provided a new idea and direction for the development of green pesticides. © 2023 Society of Chemical Industry.

Biocidal and antibiofilm activities of arginine-based surfactants against Candida isolates

Amino-acid-based surfactants are a group of compounds that resemble natural amphiphiles and thus are expected to have a low impact on the environment, owing to either the mode of surfactant production or its means of disposal. Within this context, arginine-based tensioactives have gained particular interest, since their cationic nature-in combination with their amphiphilic character-enables them to act as broad-spectrum biocides. This capability is based mainly on their interactive affinity for the microbial envelope that alters the latter's structure and ultimately its function. In the work reported here, we investigated the efficiency of Nα-benzoyl arginine decyl- and dodecylamide against Candida spp. to further our understanding of the antifungal mechanism involved. For the assays, both a Candida albicans and a Candida tropicalis clinical isolates along with a C. albicans-collection strain were used as references. As expected, both arginine-based compounds proved to be effective against the strains tested through inhibiting both the planktonic and the sessile growth. Furthermore, atomic force microscopy techniques and lipid monolayer experiments enabled us to gain insight into the effect of the surfactant on the cellular envelope. The results demonstrated that all the yeasts treated exhibited changes in their exomorphologic structure, with respect to alterations in both roughness and stiffness, relative to the nontreated ones. This finding-in addition to the amphiphiles' proven ability to insert themselves within this model fungal membrane-could explain the changes in the yeast-membrane permeability that could be linked to viability loss and mixed-vesicle release.

Piperidine based 1,2,3-triazolylacetamide derivatives induce cell cycle arrest and apoptotic cell death in Candida auris

Introduction: The fungal pathogen Candida auris, is a serious threat to public health and is associated with bloodstream infections causing high mortality particularly in patients with serious medical problems. As this pathogen is generally resistant to all the available classes of antifungals, there is a constant demand for novel antifungal drugs with new mechanisms of antifungal action.

Objective: Therefore, in this study we synthesised six novel piperidine based 1,2,3-triazolylacetamide derivatives (pta1-pta6) and tested their antifungal activity and mechanism of action against clinical C. auris isolates.

Methods: Antifungal susceptibility testing was done to estimate MIC values of piperidine derivatives following CLSI recommended guidelines. MUSE Cell Analyzer was used to check cell viability and cell cycle arrest in C. auris after exposure to piperidine derivatives using different kits. Additionally, fluorescence microscopy was done to check the effect of test compound on C. auris membrane integrity and related apoptotic assays were performed to confirm cellular apoptosis using different apoptosis markers.

Results: Out of the six derivatives; pta1, pta2 and pta3 showed highest active with MIC values from 0.24 to 0.97 μg/mL and MFC ranging from 0.97 to 3.9 μg/mL. Fungicidal behaviour of these compounds was confirmed by cell count and viability assay. Exposure to test compounds at sub-inhibitory and inhibitory concentrations resulted in disruption of C. auris plasma membrane. Further in-depth studies showed that these derivatives were able to induce apoptosis and cell cycle arrest in S-phase. Furthermore, the compounds demonstrated lower toxicity profile.

Conclusion: Present study suggests that the novel derivatives (pta1-pta3) induce apoptotic cell death and cell cycle arrest in C. auris and could be potential candidates against C. auris infections.