Fractionation of High-Value Compounds from Hops Using an Optimised Sequential Extraction Procedure.

Area of Science:

• Agricultural and Food Chemistry
• Natural Product Chemistry
• Process Chemistry

Background:

• Hops contain valuable compounds like alpha-acids, beta-acids, xanthohumol, and phenolics, which have diverse applications.
• Efficient extraction and fractionation methods are crucial for isolating these high-value compounds from hop matrices.
• Existing methods may lack optimization for maximizing recovery across different compound classes.

Purpose of the Study:

• To develop and optimize a sequential extraction and fractionation process for high-value compounds from hop pellets.
• To maximize the recovery yields of alpha-acids, beta-acids, xanthohumol, and phenolics.
• To evaluate the antioxidant properties of the extracted fractions.

Main Methods:

• Screening of ten organic solvents for solid-liquid extraction efficacy.
• Optimization of extraction variables (solvent composition, temperature, time) using a methanol-dichloromethane mixture.
• Fractionation into soft resins, hard resins, and spent solids.
• Validation of optimized conditions across six hop varieties.
• Assay of antioxidant properties using Ferric Reducing Antioxidant Power (FRAP) and radical scavenging activity (EC50).

Main Results:

• Optimized extraction at room temperature with 19.7% methanol for 89 minutes yielded high recoveries: 86.57% alpha-acids, 89.14% beta-acids (soft resins), 78.48% xanthohumol (hard resins), and 67.10% phenolics (spent solids).
• The optimized process demonstrated successful validation across six different hop varieties.
• Soft resin fractions exhibited the highest antioxidant activities, with FRAP values of 3.91 ± 0.10 g AAE/100 g and EC50 values of 0.10 ± 0.01 mg/mL.

Conclusions:

• The developed sequential extraction and fractionation process is efficient for isolating valuable compounds from hops.
• The optimized method provides high yields and demonstrates broad applicability across various hop varieties.
• The findings support the potential for large-scale industrial production of hop-derived compounds with significant antioxidant properties.