Anti-encystment and amoebicidal activity of Lonicera japonica Thunb. and its major constituent Chlorogenic acid in vitro

Objective:To examine the acanthamoebicidal effects of ethyl acetate,aqueous and butanol fractions of dried flower buds of Lonicera japonica(L.japonica) Thunb.(Flos Lonicerae) in vitro.Methods:Acanthamoeba triangularis isolates were obtained from environmental water samples and identified by PCR.They were exposed to ethyl acetate,water and butanol fractions of L.japonica Thunb.at concentrations ranging from 0.5 mg/m L to 1.5 mg/m L.The extracts were evaluated for growth inhibition at 24,48 and 72 h,respectively.Chlorogenic acid at a concentration of 1 mg/mL was examined for inhibition of encystment.Results:Ethyl acetate fraction at a concentration of 1.5 mg/mL evoked a significant reduction of trophozoite viability by 48.9% after 24 h,49.2% after 48 h and 33.7% after 72 h Chlorogenic acid,the major active constituent of L.japonica Thunb.at the concentration of 1 mg/mL reduced the cysts/trophozoite ratio by 100% after 24 h,84.0% after 48 h and 72.3% after 72 h.This phenolic compound at concentration of 1 mg/mL concurrent with 0.6% hydrogen peroxide inhibited hydrogen peroxide-induced encystment by 92.8% at 72 h.Conclusions:Results obtained from this study show that ethyl acetate fraction at 1.5 mg/m L is the most potent fraction of L.japonica Thunb.and its major constituent chlorogenic acid showed the remarkable inhibition of encystment at a concentration of 1 mg/mL.