Accumulation Patterns of Major Chemical Components during the Growth Period of Four Domestic Cultivars of Hops (Humulus lupulus L.)

In this study, the accumulation of total flavonoids, total polyphenols, α-acids, and β-acids during five growth stages (S1-S5, from the appearance of hop cones to harvest) was investigated in four domestic hop cultivars: Marco Polo, SA-1, Tsingtao Flower, and Kirin Fenglv. Total flavonoids, total polyphenols, α-acids, and β-acids were measured using spectrophotometry, and xanthohumol, isoxanthohumol, 6-prenylnaringenin (6-PN), and 8-prenylnaringenin (8-PN) were analyzed using high performance liquid chromatography (HPLC). Correlation analysis and principal component analysis (PCA) were conducted on these chemical components. A fluctuating trend was showed in the accumulation of chemical components across the growth stages, with most components reaching a peak in the mid-to-late stages before declining. Total flavonoid content peaked at S3 in all cultivars. Total polyphenol content peaked at S4 in Marco Polo and Tsingtao Flower, and at S3 in SA-1 and Kirin Fenglv. For xanthohumol, Marco Polo and SA-1 peaked at S4, while Tsingtao Flower and Kirin Fenglv peaked at S5 and S3, respectively. Isoxanthohumol peaked at S3 in Marco Polo and SA-1, and at S5 in Tsingtao Flower and Kirin Fenglv. The α-acid content reached its maximum level at S4 in all cultivars, while β-acid content peaked at S3 in Marco Polo, SA-1, and Tsingtao Flower, and at S4 in Kirin Fenglv. Significant positive correlations (P < 0.01) were observed between total flavonoids and total polyphenols in all cultivars. The comprehensive scoring suggested that S3 was the optimal harvest stage for Marco Polo, SA-1, and Kirin Fenglv, while S4 was optimal for SA-1 and Tsingtao Flower. This research provides foundational data on the dynamic accumulation of chemical components in domestic hops and also provides a scientific basis for the optimization of the harvest time, the development of bioactive components and the improvement of hop quality.