Fig. 1.

Hop α/β bitter acids composition in comparison to its cytotoxic effect. (A) Chemical structures of humulones (α-bitter acids) and lupulones (β-bitter acids) series detected in hop resin. (B) Hierarchical cluster analysis (HCA) of hop cultivars based on group average cluster analysis of its biochemical profile as the analytical data showing clustering of cultivars in 2 major groups mostly influenced by its β-bitter acids levels (μg/ml) and β/α-acid ratios. Data are mean ± SE from three independent measurements. Grey box highlights β-acids enriched resins (HSE, HHE & HHT) from other cultivars. (C) Cytotoxicity data of hops resin extracts and pure α- and β-bitter acids against human prostate (PC3) and colon (HT29) cancer cell lines (IC₅₀ values expressed in μg/ml). Detailed description of bitter acids standards composition is provided under materials and methods. Data are mean ± SE from four independent experiments. Note the grey box highlighting β-enriched resins (HSE, HHE & HHT) showed no significant difference in its IC₅₀ values from other samples.