Synergistic activity of pomegranate rind extract and Zn (II) against Candida albicans under planktonic and biofilm conditions, and a mechanistic insight based upon intracellular ROS induction

Abstract

Candida albicans is an opportunistic pathogen, which causes superficial infection and can lead to mortal systemic infections, especially in immunocompromised patients. The incidence of C. albicans infections is increasing and there are a limited number of antifungal drugs used in treatment. Therefore, there is an urgent need for new and alternative antifungal drugs. Pomegranate rind extract (PRE) is known for its broad-spectrum antimicrobial activities, including against C. albicans and recently, PRE and Zn (II) have been shown to induce synergistic antimicrobial activity against various microbes. In this study, the inhibitory activities of PRE, Zn (II) and PRE in combination with Zn (II) were evaluated against C. albicans. Antifungal activities of PRE and Zn (II) were evaluated using conventional microdilution methods and the interaction between these compounds was assessed by in vitro checkerboard and time kill assays in planktonic cultures. The anti-biofilm activities of PRE, Zn (II) and PRE in combination with Zn (II) were assessed using confocal laser scanning microscopy, with quantitative analysis of biofilm biomass and mean thickness analysed using COMSTAT2 analysis. In addition, antimicrobial interactions between PRE and Zn (II) were assayed in terms reactive oxygen species (ROS) production by C. albicans. PRE and Zn (II) showed a potent antifungal activity against C. albicans, with MIC values of 4 mg/mL and 1.8 mg/mL, respectively. PRE and Zn (II) in combination exerted a synergistic antifungal effect, as confirmed by in vitro checkerboard and time kill assays. PRE, Zn (II) and PRE and Zn (II) in combination induced significant reductions in biofilm biomass, but only PRE caused a substantial reduction in biofilm mean thickness. PRE and Zn (II) in combination caused the highest levels of ROS production by C. albicans, in both planktonic and biofilm forms. PRE, Zn (II) and PRE and Zn (II) in combination possess potent antifungal activity against C. albicans in both planktonic and biofilm forms. PRE and Zn (II) further exhibited a synergistic antifungal activity via the induction of excessive ROS accumulation in C. albicans under both planktonic and biofilm forms, which may contribute to their antifungal effects.

Characterization, Antimicrobial Activity, and Antioxidant Efficacy of a Pomegranate Peel Solution Against Persistent Root Canal Pathogens

“…The polyphenolic and tannin compounds (as the punicalagin) promote the antimicrobial activity of the PGE through the precipitation of proteins on the cell surface of the microorganism and inhibiting metabolic enzymes that cause cell lysis [16,28]. The preparation method and chemical characterization of tested extracts are essential because their activity is directly affected by the plant part, plant age, season of collection, drying strategy, and extraction procedure [3].…”

“…Determination of the punicalagin content in the PGE was carried out by UPLC using pure punicalagin as the standard (Sigma-Aldrich, St Louis, USA) [16].…”

“…Adjuvant therapies have been evaluated to improve the canal system disinfection and root filling quality 1 [2,[4][5][6]. Natural bioactive products have been tested for antioxidant and antimicrobial properties [7][8][9][13][14][15][16][17].…”

“…Previous studies have evaluated the antimicrobial and antioxidant activities of pomegranate peel extracts [4,8,13,16,17,25], including two studies that tested it inside the root canal system as an intracanal medicament [4,8]. Most studies have used an aqueous extract instead of hydroalcoholic [4,8,17], which can compromise the amount of phytochemicals in the solution.…”

“…Others did not evaluate the pomegranate solution against persistent root canal pathogens [16,17,25].…”