Modulation of the phytoestrogenicity of beer by monoterpene alcohols present in various hop oil fractions

Abstract

The estrogenicity of beer, due to prenylated flavonoids, mainly 8-prenylnaringenin, can be modulated under suitable conditions, whereby monoterpene alcohols present in hop oils act as precursors for prenylation of flavonoids. Four hop oil fractions, 'citrussy', 'estery', 'floral', and 'spicy', respectively, were investigated as potential sources. The main constituents were separated and identified by gas chromatography - mass spectroscopy (GC-MS). They were related to 8-prenylnaringenin via their MS features, while the ability to deliver a prenyl residue was evaluated by selected ion monitoring of fragment ions m/z 69 and m/z 41. In particular, the citrussy hop oil fraction proved to be a rich source of precursors for prenyl residues and linalool, the main constituent in the citrussy and spicy hop oil fractions, was shown to be most prominent. The process was highlighted by an increase in the content of 8-prenylnaringenin on forced ageing of acidified beer spiked with naringenin and linalool.