Water infusions of Ligustrum delavayanum and Ligustrum vulgare leaves and eight phenolics isolated therefrom have been assayed in vitro on ofloxacin-induced genotoxicity in the unicellular flagellate Euglena gracilis. The tested compounds luteolin, quercetin, luteolin-7-glucoside, luteolin-7-rutinoside, quercetin-3-rutinoside, apigenin-7-rutinoside, tyrosol and esculetin inhibited the mutagenic activity of ofloxacin (43 microM) in E. gracilis. Water infusions from leaves of L. delavayanum and L. vulgare showed higher antimutagenic effect (p(t) < 0.001). The activity of these samples against ofloxacin (86 microM)-induced genotoxicity was lower, but statistically significant (p(t) < 0.05), excluding the water infusion of L. delavayanum leaves (p(t) < 0.01). Efficacy of quercetin, luteolin-7-rutinoside, apigenin-7-rutinoside was insignificant. The antimutagenic effect of most phenolics we studied could be clearly ascribed to their DPPH scavenging activity, substitution patterns and lipophilicity.