| Abstract
| - Nowadays, hop is used almost exclusively by brewers for bitterness and flavor. Although hoppolyphenols have been widely studied in the past decade for their antioxidant activity in the boilingkettle, very little is known about their real impact on health. The discovery of resveratrol in hop pelletshighlights the potential health-promoting effect of moderate beer consumption. Here, we haveoptimized a quantitative extraction procedure for resveratrol in hop pellets. Preliminary removal ofhydrophobic bitter compounds with toluene and cyclohexane at room temperature allows 99% trans-resveratrol recovery by ethanol:water (75:25, v/v) solid/liquid extraction at 60 °C. Reverse phaseliquid chromatography proves an excellent means of separating isomers. In addition, we havecompared two mass spectrometry ionization methodsatmospheric pressure chemical ionization(APCI) and electrospray ionization (ESI)in both the positive and the negative modes. On the basisof standard additions applied with the optimized extraction procedure and reverse phase high-performance liquid cromatography−APCI(+)−tandem mass spectrometry, it appears that Tomahawkhop pellets (T90, harvest 2002) contain 0.5 ppm trans-resveratrol, 2 ppm trans-piceid, no cis-resveratrol, and 0.9 ppm cis-piceid. Keywords: Hop; extraction; resveratrol; polyphenols; health; HPLC-MS/MS; APCI; ESI
|
