Composition and variability of phenolic compounds in Origanum vulgare from Lithuania

Abstract

The study has contributed to the primary knowledge on Origanum vulgare phenolic compounds from Lithuania. The composition of ethanolic extracts from flowers, leaves and stems of 18 field accessions of O. vulgare was analysed by the HPLC method. Fourteen phenolic compounds, namely rosemarinic acid, chlorogenic acid, caffeic acid, hyperozide, naringin + rutin, luteolin, astragalin, vitexin, isovitexin, eriodictol, quercetin, naringenin were identified in the plant material. Rosemarinic acid was the dominant compound; its content in flower extracts ranged within 0.99–9.65 mg/g, in leaves 1.11–7.42 mg/g and in stems 0.53–0.77 mg/g dry weight. Analysis of variance illustrated differences in the content of compounds among flowers, leaves and stems. The most distinct differences were observed in respect of the content of hyperozide, rosemarinic acid, chlorogenic acid, luteolin and quercetin. In order to study the infraspecific variability, the results of chemical analysis were submitted to a hierarchical cluster analysis. The flower extracts were allotted to five groups on the basis of phenolics quantitatives, whereas leaf extracts showed differences among four clusters. The chemical variability of the analysed accessions seems likely to result from the genetic variability, since the influence of environmental factors has been eliminated. Keywords: Origanum vulgare, field accessions, phenolic compounds, HPLC method, chemical polymorphism