Summary Evaluation of bitter acids and polyphenols content in Czech hops harvest in 2013 - I: Contents of α- and β-Bitter Acids.

The contents of polyphenolic compounds and the antioxidative properties of the important Czech hop varieties Saaz, Sladek, Premiant and Agnus were evaluated in selected samples (24, 12, 12 and 4). The hops were extracted with a water/acetone solution, and then analyzed. The results were compared with those from hops harvested in 2011 and 2012. The content of total polyphenols (TP), which are important in terms of the Protected Geographical Indication (PGI) as well as the contents of anthocyanogens and flavonoids are dependent on the variety. The highest content was found in the Saaz variety and the lowest in the Sladek variety. The ratios of TP to α-acids decrease in the order Saaz, Sladek, Premiant and Agnus. The only significant difference resulted between the Saaz variety and the other varieties. The antiradical activity of the hops varieties Saaz, Premiant and Agnus harvested 2013 was about 15 % rel. lower than in 2012. The antiradical activity of the Sladek variety was even 25% rel. lower. The highest content of the dominantly present prenylflavonoid xanthohumol (XN) was found in the Agnus variety (7.73 mg/g) followed by the varieties Sladek (5.21 mg/g), Premiant (3.54 mg/g) and Saaz (2.59 mg/g). The XN contents in the single hops varieties were relatively well balanced with relative standard deviations (RSD) from 8.0% to 15.9%. They were significantly lower in the varieties Saaz (by 24.3%) and Premiant (by 15.2%) when compared with the harvest 2012. The ratio of XN to α-acids was highest in the Saaz variety and lowest in the Premiant variety. The average contents of the phytoestrogen, 8-prenylnaringenine in the Sladek, Premiant and Agnus varieties harvested in 2013 varied from 29 to 33 µg/g. A lower content was found in the Saaz variety (22 µg/g). The contents of XN and other prenylflavonoids such as 6-prenylnaringenine and isoxanthohumol depend strongly on the year of the harvest. The highest values were found in hops harvested in 2012 followed by the years 2013 and 2011.The contents of polyphenolic compounds and the antioxidative properties of the important Czech hop varieties Saaz, Sladek, Premiant and Agnus were evaluated in selected samples (24, 12, 12 and 4). The hops were extracted with a water/acetone solution, and then analyzed. The results were compared with those from hops harvested in 2011 and 2012. The content of total polyphenols (TP), which are important in terms of the Protected Geographical Indication (PGI) as well as the contents of anthocyanogens and flavonoids are dependent on the variety. The highest content was found in the Saaz variety and the lowest in the Sladek variety. The ratios of TP to α-acids decrease in the order Saaz, Sladek, Premiant and Agnus. The only significant difference resulted between the Saaz variety and the other varieties. The antiradical activity of the hops varieties Saaz, Premiant and Agnus harvested 2013 was about 15 % rel. lower than in 2012. The antiradical activity of the Sladek variety was even 25% rel. lower. The highest content of the dominantly present prenylflavonoid xanthohumol (XN) was found in the Agnus variety (7.73 mg/g) followed by the varieties Sladek (5.21 mg/g), Premiant (3.54 mg/g) and Saaz (2.59 mg/g). The XN contents in the single hops varieties were relatively well balanced