Potentiation of pomegranate rind extract (PRE) bactericidal activity by ZnSO4 combination

Abstract

The addition of Zn(II) to PRE was previously found to increase virucidal activity of PRE by seven log reduction in plaque forming units against Herpes simplex virus. This thesis tested the same system for antibacterial and bactericidal activity against bacteria that are often associated with skin and wound infections. Antibacterial synergistic activity of PRE + Zn(II) was tested using a checkerboard test and showed synergy with MRSA and S. epidermidis with FIC index ≤0.5 and MIC level of PRE in the combination at (62.5, 31.25 μg/mL) and Zn(II) at (1600, 400 μM). In addition, suspension time-kill testing showed synergistic bactericidal activity with PRE 1 mg/mL + ZnSO4 (0.125 and 0.25M). The cytotoxicity of PRE ± Zn(II) was investigated using MTT and FACS analyses, short term exposure showed that PRE (5-50 μg/mL) was tolerated and no significant toxicity on HaCaT cell line was observed. In vitro scratch wound model was investigated and showed that PRE at lower levels mediates HaCaT cell migration compared to untreated group. Significant cell migration mediation was observed with PRE 10 μg/mL and Zn(II) (25-100 μM), as did the combination that contained PRE (5, 10 μg/mL) with ZnSO4 50 μM. Optimization of topical hydrogel formulations resulted in three formulations that showed promising permeation and penetration profiles using in vitro porcine epidermis. Formulations applied to inoculated porcine in simulated in-use conditions again demonstrated syndergistic bactericidal activity of PRE + Zn(II) with >5 log reduction in MRSA inoculated porcine kin after 20 minutes contact time compared to ~1 log reduction for the control.