Xanthohumol and related prenylflavonoids from hops and beer: to your good health!

Pharmacognostic and pharmacological profile of Humulus Lupulus L.

Flavonoids and their glycosides, including anthocyanins

Solid phase microextraction (SPME) is a convenient and efficient extraction method that involves using a thin polymer film coating on a fine silica fiber to adsorb analytes of interests from a sample matrix. A theoretical model is proposed to deal with the dynamic adsorption process of SPME. In this model, mass diffusion from the matrix to the SPME polymer film is considered as the rate-determining step in reaching an adsorption equilibrium, and a steady-state diffusion is assumed for SPME in an effectively agitated sampling medium. Mathematical treatment of the adsorption process generates an expression that can describe experimental adsorption time profiles of the SPME process. The expression also provides a directly proportional relationship between the amount of analyte adsorbed by the SPME fiber and its initial concentration in the sample matrix. This relationship indicates that SPME quantification is feasible before an adsorption equilibrium is reached, once the agitation condition and the sampling ...

Solid Phase Microextraction for Quantitative Analysis in Nonequilibrium Situations

Prenylated flavonoids found in hops and beer, i.e., prenylchalcones and prenylflavanones, were examined for their ability to inhibit in vitro oxidation of human low-density lipoprotein (LDL). The oxidation of LDL was assessed by the formation of conjugated dienes and thiobarbituric acid-reactive substances (TBARS) and the loss of tryptophan fluorescence. At concentrations of 5 and 25 μM, all of the prenylchalcones tested inhibited the oxidation of LDL (50 μg protein/ml) induced by 2 μM copper sulfate. The prenylflavanones showed less antioxidant activity than the prenylchalcones, both at 5 and 25 μM. At 25 μM, the nonprenylated chalcone, chalconaringenin (CN), and the nonprenylated flavanone, naringenin (NG), exerted prooxidant effects on LDL oxidation, based on TBARS formation. Xanthohumol (XN), the major prenylchalcone in hops and beer, showed high antioxidant activity in inhibiting LDL oxidation, higher than α-tocopherol and the isoflavone genistein but lower than the flavonol quercetin. When combined,...

Antioxidant and Prooxidant Actions of Prenylated and Nonprenylated Chalcones and Flavanones in Vitro

Prenylflavonoid variation in Humulus lupulus: distribution and taxonomic significance of xanthogalenol and 4′-O-methylxanthohumol

A solid-phase microextraction (SPME) method is described for the determination of the essential oils, humulene and caryophyllene, in the headspace of female hop cones and male hop lupulin samples. Optimized SPME sampling parameters for the determination of the humulene to caryophyllene (H/C) ratio for female hops (50 mg) and male lupulin (25 mg) samples include a 100 μm poly(dimethylsiloxane) SPME fiber and a 4 h sample exposure period at a temperature of 50 °C. Increasing the temperature to 90 °C or increasing the length of sample exposure at 50 °C promoted caryophyllene oxidation. In a survey of five female hop varieties, good agreement was found between the H/C ratio obtained by headspace SPME and conventional steam distillation. The H/C ratio for 10 male lupulin varieties determined by headspace SPME and pentane extraction also indicated good agreement between the two extraction methods. Keywords: Hops; essential oils; SPME; headspace analysis

Determination of Essential Oils in Hops by Headspace Solid-Phase Microextraction†

Floral hop aroma in beer

More than 250 essential oil components have been identified in hops by capillary gas chromatography. The hop aroma component profile (HACP), quantitatively measured as nanoliters per gram of hops (...

Gail B. Nickerson

Papers

Prenylflavonoid variation in Humulus lupulus: distribution and taxonomic significance of xanthogalenol and 4′-O-methylxanthohumol

Determination of Essential Oils in Hops by Headspace Solid-Phase Microextraction†

Floral hop aroma in beer

Hop Aroma component profile and the aroma unit

Comparative chemical attributes of native North American hop, Humulus lupulus var. lupuloides E. Small