Synergistic antifungal activity of berberine derivative B-7b and fluconazole

PLoS One. 2015 May 19;10(5):e0126393. doi: 10.1371/journal.pone.0126393. eCollection 2015.

Abstract

Our previous study demonstrated berberine (BBR) and fluconazole (FLC) used concomitantly exhibited a synergism against FLC-resistant Candida albicans in vitro. We also suggested BBR played a major antifungal role in the synergism of FLC and BBR, while FLC increased intracellular BBR concentrations. Our following systematic structural modification and reconstruction of BBR core identified the novel scaffold of N-(2-(benzo[d][1,3]dioxol-5-yl)ethyl)-2-(substituted phenyl)acet-amide derivatives 7a-i, including B-7b and B-7d exhibiting remarkable synergistic antifungal activity and low cytotoxicity. Here, the study mainly investigated the synergistic activity of FLC and B-7b and the underlying mechanism. In vitro interaction of FLC and B-7b was investigated against 30 FLC-resistant clinical isolates of C. albicans and non-C. albicans species, including Candida tropicalis, Candida parapsilosis, Candida glabrata, Candida krusei and Cryptococcus neoformans. The potent synergistic activity of B-7b in combination with FLC against FLC-resistant C. albicans was found through the checkerboard microdilution assay. The findings of agar diffusion tests and time-kill curves confirmed its better synergism with FLC. And as expected, B-7b exhibited much lower cytotoxicity than BBR to human umbilical vein endothelial cells. In contrast to BBR, we found that endogenous ROS augmentation was not involved in the synergism of FLC and B-7b. According to the results from our present comparative proteomic study, it seemed that the disruption of protein folding and processing and the weakening of cells' self-defensive ability contributed to the synergism of FLC and B-7b. Together, these results suggested novel scaffold BBR derivative B-7b could be a promising synergist in combination with FLC for the treatment of invasive fungal infections.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antifungal Agents / pharmacology*
  • Berberine / pharmacology*
  • Candida / drug effects
  • Cryptococcus neoformans / drug effects
  • Drug Resistance, Fungal
  • Drug Synergism
  • Fluconazole / pharmacology*
  • Microbial Sensitivity Tests

Substances

  • Antifungal Agents
  • Berberine
  • Fluconazole

Grants and funding

This study was supported by the National Science Foundation of China(81330083,81202563,81471924), National Key Basic Research Program of China (No 2013CB531602), National Science and Technology Major Project for the Creation of New Drugs (No 2013ZX09103001-014), the Shanghai Science and Technology Support Program (No 14401902200, No 14431902200), National Science and Technology Major Project for the Creation of New Drugs (No 2013ZX09J13108-03B); the Shanghai Manufacture-Education-Research-Medical Cooperative Project (No 12DZ1930505).