Hesperetin—Between the Ability to Diminish Mono- and Polymicrobial Biofilms and Toxicity

Hesperetin is the aglycone of citrus flavonoid hesperidin. Due to the limited information regarding hesperetin antimicrobial potential and emerging need for novel antimicrobials, we have studied its antimicrobial activity (microdilution assay), antibiofilm activity with different assays in two models (mono- and polymicrobial biofilm), and toxicity (MTT and brine shrimp lethality assays). Hesperetin inhibited growth of all Candida isolates (minimal inhibitory concentration, MIC, 0.165 mg/mL), while it’s inhibitory potential towards Staphylococcus aureus was lower (MIC 4 mg/mL). Hesperetin (0.165 mg/mL) reduced ability of Candida to form biofilms and moderately reduced exopolysaccharide levels in biofilm matrix. Effect on the eradication of 24 h old C. albicans biofilms was promising at 1.320 mg/mL. Inhibition of staphylococcal biofilm formation required higher concentrations of hesperetin (<50% inhibition with MIC 4 mg/mL). Establishment of polymicrobial C. albicans-S. aureus biofilm was significantly inhibited with the lowest examined hesperetin concentration (1 mg/mL) in crystal violet and CFU assays. Hesperetin toxicity was examined towards MRC-5 fibroblasts (IC(50) 0.340 mg/mL) and in brine shrimp lethality assay (LC(50) > 1 mg/mL). Hesperetin is efficient in combating growth and biofilm formation of Candida species. However, its antibacterial application should be further examined due to the cytotoxic effects provoked in the antibacterial concentrations.