Synergistic Interactions of Eugenol-tosylate and Its Congeners with Fluconazole against Candida albicans
作者:Aijaz Ahmad、Mohmmad Younus Wani、Amber Khan、Nikhat Manzoor、Julitha Molepo
DOI:10.1371/journal.pone.0145053
日期:——
We previously reported the antifungal properties of a monoterpene phenol “Eugenol” against different Candida strains and have observed that the addition of methyl group to eugenol drastically increased its antimicrobial potency. Based on the results and the importance of medicinal synthetic chemistry, we synthesized eugenol-tosylate and its congeners (E1-E6) and tested their antifungal activity against different clinical fluconazole (FLC)- susceptible and FLC- resistant C. albicans isolates alone and in combination with FLC by determining fractional inhibitory concentration indices (FICIs) and isobolograms calculated from microdilution assays. Minimum inhibitory concentration (MIC) results confirmed that all the tested C. albicans strains were variably susceptible to the semi-synthetic derivatives E1-E6, with MIC values ranging from 1–62 μg/ml. The test compounds in combination with FLC exhibited either synergy (36%), additive (41%) or indifferent (23%) interactions, however, no antagonistic interactions were observed. The MICs of FLC decreased 2–9 fold when used in combination with the test compounds. Like their precursor eugenol, all the derivatives showed significant impairment of ergosterol biosynthesis in all C. albicans strains coupled with down regulation of the important ergosterol biosynthesis pathway gene-ERG11. The results were further validated by docking studies, which revealed that the inhibitors snugly fitting the active site of the target enzyme, mimicking fluconazole, may well explain their excellent inhibitory activity. Our results suggest that these compounds have a great potential as antifungals, which can be used as chemosensitizing agents with the known antifungal drugs.
我们以前曾报道过一种单萜酚 "丁香酚 "对不同念珠菌菌株的抗真菌特性,并观察到在丁香酚中加入甲基可大大提高其抗菌效力。基于上述研究结果和药物合成化学的重要性,我们合成了丁香酚对甲苯磺酸酯及其同系物(E1-E6),并通过测定微量稀释试验计算出的分数抑制浓度指数(FICIs)和等分图,测试了它们单独或与 FLC 联用对不同临床氟康唑(FLC)敏感和 FLC 耐药白念珠菌分离株的抗真菌活性。最低抑菌浓度(MIC)结果证实,所有受试白僵菌菌株对半合成衍生物 E1-E6 均有不同程度的敏感性,MIC 值范围为 1-62 μg/ml。测试化合物与 FLC 的组合显示出协同作用(36%)、相加作用(41%)或不相干作用(23%),但未观察到拮抗作用。FLC 与试验化合物联用时,其 MICs 降低了 2-9 倍。与它们的前体丁香酚一样,所有衍生物都对所有白僵菌菌株的麦角固醇生物合成产生了显著的抑制作用,同时还下调了重要的麦角固醇生物合成途径基因-ERG11。对接研究进一步验证了这一结果,研究发现抑制剂与目标酶的活性位点紧密贴合,模拟氟康唑,这很好地解释了它们出色的抑制活性。我们的研究结果表明,这些化合物具有作为抗真菌药物的巨大潜力,可与已知的抗真菌药物一起用作化学增敏剂。