Hop (Humulus lupulus L.) Phenolic Compounds Profile Depends on Cultivar and Plant Organ Maturity

Area of Science:

• Agricultural Chemistry
• Plant Biochemistry
• Phytochemistry

Background:

• Hop by-products, primarily cones, are a significant biomass source for the brewing industry.
• Phenolic compounds (PCs) in hops possess potential applications in the food and pharmaceutical sectors.
• Accurate qualitative and quantitative analysis of PCs is crucial for their industrial utilization.

Purpose of the Study:

• To determine the influence of hop cultivar, plant organ, and plant level on phenolic compound profiles.
• To investigate the variability of PC content and composition within different parts and positions of hop plants.
• To establish a basis for optimizing the extraction and utilization of valuable PCs from hop biomass.

Main Methods:

• Analysis of phenolic compounds in cones, leaves, and stalks of three Polish hop cultivars (Marynka, Lubelski, Magnum).
• Sampling was conducted at three distinct levels within each plant to assess positional effects.
• Metabolomic profiling was employed to identify and quantify major phenolic compounds.

Main Results:

• Phenolic compound content varied significantly across hop cultivars, plant organs, and plant levels, indicating differential maturity.
• Leaves exhibited the highest total PC content (up to 922 mg/100 g), followed by cones (up to 421 mg/100 g) and stalks (up to 105 mg/100 g).
• Kaempferol-3-glucoside and rutin were the predominant PCs in leaves, while rutin was the main PC in cones.

Conclusions:

• Plant organ and position (level) are critical factors influencing phenolic compound profiles in hops, beyond just the cultivar.
• Understanding this variability allows for targeted harvesting and processing of hop biomass to maximize PC yield and purity.
• These findings support the valorization of hop by-products as a sustainable source of valuable phenolic compounds for industrial applications.