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A rapid reversed-phase (RP) high-performance liquid chromatography method was developed and applied for simultaneous separation, and determination of flavonoids and phenolic acids in eight Plantago L. taxa (P. altissima L., P. argentea Chaix, P. coronopus L., P. holosteum Scop. ssp. depauperata Pilger, P. holosteum ssp. holosteum, P. holosteum ssp. scopulorum (Degen) Horvatić, P. lagopus L., and P. maritima L.) growing in Croatia. Chromatographic separation was carried out on Zorbax Eclipse XDB-C18 using gradient elution with a H2 O (pH 2.5, adjusted with CF3 COOH) and MeCN mixture at 30°. The contents of analyzed phenolic compounds (% of the dry weight of the leaves, dw) varied among examined species: rutin (max. 0.024%, P. argentea), hyperoside (max. 0.020%, P. lagopus), quercitrin (max. 0.013%, P. holosteum ssp. holosteum), quercetin (max. 0.028%, P. holosteum ssp. scopulorum), chlorogenic acid (max. 0.115%, P. lagopus), and caffeic acid (max. 0.046%, P. coronopus). Isoquercitrin was detected only in P. argentea (0.020%), while isochlorogenic acid content was below limit of quantification in all investigated species. Multivariate analyses (UPGMA and PCA) showed significant differences in contents of investigated polyphenolic compounds between different Plantago taxa. Accordingly, investigated substances might be employed as chemotaxonomic markers in the study of the complex genus Plantago.

This study investigates antioxidant capacity and protective effects of phenolic compounds oleuropein (OLP) and hydroxytyrosol (HT), present in olive oil and olive leaves, against H2O2-induced DNA damage in human peripheral lymphocytes. Antioxidant potency was determined using the measurement of radical-scavenging activity (ABTS∙+ assay), ferric reducing power (FRAP assay) and cupric reducing antioxidant capacity (CUPRAC assay). Both substances were found to be potent antioxidant agents due to their free radical-scavenging activities. Antigenotoxic effects of oleuropein and hydroxytyrosol against H2O2-induced damage in human lymphocytes were evaluated in vitro by alkaline comet assay. At tested concentrations (1, 5, 10 µmol L−1), oleuropein and hydroxytyrosol did not induce a significant increase of primary DNA damage in comparison with the negative control. Pretreatment of human lymphocytes with each of the substances for 120 min produced a dose-dependent reduction of primary DNA damage in the tested cell type. Hydroxytyrosol showed a better protective effect against H2O2-induced DNA breaks than oleuropein which could be associated with their free radical-scavenging efficacy.