title: Lichen endophyte derived pyridoxatin inactivates Candida growth by interfering with ergosterol biosynthesis.
abstract: BACKGROUND
  This study is to characterize the antifungal effects of pyridoxatin (PYR), a small natural product isolated from an endolichenic fungus.
  
  
  METHODS
  The susceptibility tests in vitro and in vivo by using Caenorhabditis elegans as an infectious model were performed to evaluate the antifungal efficacy of PYR against Candida species. The cytotoxicity of PYR against normal human cells was tested using MTT assay. The transcriptional levels of genes related to sterol synthesis and cell cycle regulation were measured using real-time quantitative PCR (qPCR). The contents ergosterol, squalene, lanosterol were detected by liquid chromatography/tandem mass spectrometry (LC/MS).
  
  
  RESULTS
  PYR was effective against four tested Candida species with its minimal inhibitory concentrations (MICs) ranging from 1-4μg/ml. No obvious cytotoxicity was observed for PYR against normal human cells. PYR inhibited the growth of Candida albicans, preventing the biofilm formation. And the antifungal action was independent on efflux pumps. The in vivo test showed PYR greatly prolonged the survival of infected C. elegans. qPCR results revealed that most of the genes related to sterol biosynthesis were considerably down-regulated in PYR-treated cells. Determination of the sterol content found that PYR inhibited the ergosterol synthesis dose dependently and caused the accumulation of squalene and lanosterol. Moreover, analysis of the structure-activity relationship revealed the heterocyclic hydroxamic acid in PYR was the key group for the antifungal action.
  
  
  CONCLUSIONS
  PYR interferes with the ergosterol synthesis to exert antifungal action.
  
  
  CONCLUSIONS
  The elucidated mechanism provides possible applications of PYR in fighting clinical relevant fungal infections.
authors.affiliation: Department of Natural Product Chemistry, Key Lab of Chemical Biology of Ministry of Education, Shandong University, No. 44 West Wenhua Road, Jinan City, Shandong Province, China.
authors.forename: Wenqiang
authors.initials: W
authors.lastname: Chang
authors.affiliation: Department of Natural Product Chemistry, Key Lab of Chemical Biology of Ministry of Education, Shandong University, No. 44 West Wenhua Road, Jinan City, Shandong Province, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Department of Natural Product Chemistry, Key Lab of Chemical Biology of Ministry of Education, Shandong University, No. 44 West Wenhua Road, Jinan City, Shandong Province, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Natural Product Chemistry, Key Lab of Chemical Biology of Ministry of Education, Shandong University, No. 44 West Wenhua Road, Jinan City, Shandong Province, China.
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Natural Product Chemistry, Key Lab of Chemical Biology of Ministry of Education, Shandong University, No. 44 West Wenhua Road, Jinan City, Shandong Province, China.
authors.forename: Yanhui
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Natural Product Chemistry, Key Lab of Chemical Biology of Ministry of Education, Shandong University, No. 44 West Wenhua Road, Jinan City, Shandong Province, China.
authors.forename: Zhiyu
authors.initials: Z
authors.lastname: Xie
authors.affiliation: Department of Natural Product Chemistry, Key Lab of Chemical Biology of Ministry of Education, Shandong University, No. 44 West Wenhua Road, Jinan City, Shandong Province, China. Electronic address: louhongxiang@sdu.edu.cn.
authors.forename: Hongxiang
authors.initials: H
authors.lastname: Lou
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D002175:Candida / Q000187:drug effects* / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D003510:Cyclohexanes / Q000494:pharmacology; D060026:Endophytes / Q000737:chemistry*; D004875:Ergosterol / Q000096:biosynthesis*; D008011:Lichens / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D013329:Structure-Activity Relationship
chemical_list: D000935:Antifungal Agents; D003510:Cyclohexanes; C069924:pyridoxatin; D004875:Ergosterol
keywords: Candida; Ergosterol; Heterocyclic hydroxamic acid; Pyridoxatin