title: In vitro activities of retigeric acid B alone and in combination with azole antifungal agents against Candida albicans.
abstract: The vitro antifungal activity of retigeric acid B (RAB), a pentacyclic triterpenoid from the lichen species Lobaria kurokawae, was evaluated alone and in combination with fluconazole, ketoconazole, and itraconazole against Candida albicans using checkerboard microdilution and time-killing tests. The MICs for RAB against 10 different C. albicans isolates ranged from 8 to 16 microg/ml. A synergistic action of RAB and azole was observed in azole-resistant strains, whereas synergistic or indifferent effects were observed in azole-sensitive strains when interpreted by a separate approach of the fractional inhibitory concentration index and DeltaE model (the difference between the predicted and measured fungal growth percentages). In time-killing tests, we used both colony counts and a colorimetric assay to evaluate the combinational antifungal effects of RAB and azoles, which further confirmed their synergistic interactions. These findings suggest that the natural product RAB may play a certain role in increasing the susceptibilities of azole-resistant C. albicans strains.
authors.affiliation: School of Pharmaceutical Sciences, Shandong University, Jinan, China.
authors.forename: Lingmei
authors.initials: L
authors.lastname: Sun
authors.forename: Shujuan
authors.initials: S
authors.lastname: Sun
authors.forename: Aixia
authors.initials: A
authors.lastname: Cheng
authors.forename: Xiuzhen
authors.initials: X
authors.lastname: Wu
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Hongxiang
authors.initials: H
authors.lastname: Lou
mesh_terms: D000935:Antifungal Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001393:Azoles / Q000008:administration & dosage / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects*; D015725:Fluconazole / Q000494:pharmacology; D017964:Itraconazole / Q000494:pharmacology; D007654:Ketoconazole / Q000494:pharmacology; D008011:Lichens / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D014315:Triterpenes / Q000009:adverse effects / Q000494:pharmacology*
chemical_list: D000935:Antifungal Agents; D001393:Azoles; D014315:Triterpenes; C540615:retigeric acid B; D017964:Itraconazole; D015725:Fluconazole; D007654:Ketoconazole