Plant-part specific and temporal variation in phenolic compounds of boreal bilberry ( Vaccinium myrtillus) plants

Abstract

Leaves and stems of bilberry were analysed for phenolic metabolites using a simple method of extraction and HPLC analysis. Hydroxycinnamic acid derivatives (HCAs) and flavonoids were identified on the basis of their UV-spectra. Temporal fluctuations in the levels of selected phenolic compounds were followed during the growth season of 2000. Qualitative and quantitative differences were detected in phenolic profiles between leaf and stem tissues. The most abundant peak in leaf samples was tentatively identified as chlorogenic acid (5- O-caffeoylquinic acid). In stems, this compound was found at much lower levels than in leaves and an unidentified p-coumaric acid derivative dominated the phenolic profile. The most abundant flavonols in leaves and stems were quercetin derivatives. The total sum of methanol-soluble phenolics was generally higher in leaves than in stems. The concentrations of some alkaline hydrolysis products were higher in stems than in leaves, indicating that a larger part of the phenolic pool was incorporated into lignified cell walls in the stems. Individual phenolic compounds differed in their seasonal fluctuation patterns. It is suggested that the observed plant-part specific and within-seasonal variation may influence the ecological interactions between bilberry and its natural enemies.