Hop resins

Maturing improves the taste and aroma of beer and the elimination of tannin, protein, and hop resins also has a beneficial effect. Some metaboHc products of unpleasant taste are further converted or washed out by the carbon dioxide surplus. The time for 1 agering varies with different types of beer. For every type of beer there is an optimal 1 agering time, and longer ] agering is usually detrimental to beer quaHty. The fiHed 1 agering tanks are subjected to the saturating pressure of carbon dioxide, usually 50—70 kPa (ca 0.5—0.7 atm), controUed by a safety valve. 

Liquid Chromatography of Hop Resin Components and Related Substances... 

The humulones 23a-d have been known for many years, but they can still be considered as a topical family of natural products (Figure 8). Found in hop resins and brewing hops, these natural ortho-quinols aroused early interest because of their antibiotic and tuberculostatic properties. Oxidative dearomatizing hydroxylation of their phenolic parents 24a-d was used in their synthesis [1]. 

After giving written informed consent, subjects provided a blood sample for a complete metabolic panel (blood chemistry and hematology), which the PI reviewed before the start of the study. On the test day, each subject s medical history was taken, and a brief medical exam was performed. Subjects were thrai randomized to one of three test groups to receive either a single dose of ibuprofen 400 mg a single dose of hops resin 450 mg or four doses of hops powder 300 mg, one dose every 2 horns for 6 horns (Table 4.2). 

Subjects provided either 7 (hops resin 450 mg and ibuprofen group) or 9 (hops powder 1200 mg in 4 divided doses group) blood draws and took either 1 or 4 doses of product, over a 9-h test-day. 

Hops resin 150 mg hops aipha acids (from hops [humulus lupulus, ieaves, flowers] extract) 10 iU naturai Vitamin E (from 8 mg d-aipha tocopheroi acetate) 0.5 mg astaxanthin (from Haematococcus pluvialis aigai extract) 1.5 mg camosic acid (from rosemary [Rosemarinus officinalis, ieaves, flowers] extract) 100 mg olive oil... 

Plasma from subjects who had taken dther a single dose of hops resin 450 mg, or hops powder 1200 mg in 4 divided doses, showed statistically significant Cox-2 selectivity, which was in turn significantly different from the Cox-1 selectivity of the ibuprofen refraence group. The 9-hour Cox-2 selectivity ratios of hops powder 1200 mg and hops resin 450 mg (0.44 and 0.42, respectively) are in the range of... 

Meloxicam 7.5 mg Nabumetone 500 mg Etodolac 200 mg Naproxen 500 mg Hops resin 450 mg Hops powder 1200 me Ibuprofen 400 mg... 

Authoritative recommendations concerning the nomenclature of hop resin components, published in 1969 [4], defined inter alia ... 

It is difficult to write a single structure for the majority of hop resins because they exhibit keto-enol tautomerism whereby ketones exist in equilibrium with the related enol ... 

Most of the hop resins contain -di- and p-tri-carbonyl functions which are enolized. It is seldom possible to isolate the individual tautomers but estimates of the relative proportions can be obtained by proton magnetic resonance (PMR) spectroscopy and other physical methods. Irrespective of the major component a tautomeric mixture can react in any form if, for example, a minor tautomer is consumed in a reaction it will be regenerated from the major tautomers, according to the equilibrium, until the reaction is complete. Thus phloroglucinol, the parent of the hop resin, exists almost entirely in the trienol form (17) but can react as cyclohexone-1,3,5 trione (18) to form a trioxime (19). 

The biosynthesis of the hop resins occurs by similar routes. Experiments with radioactively labelled substrates have established that the phloroglucinol nucleus is formed from three molecules of acetic acid and not from sugars or shikimate. The acyl side-chains are formed from amino acids or intermediates in their biosynthesis. Thus, in humulone and lupulone they arise from leucine, in the co-analogues from valine, and in the ad-analogues from isoleucine. The amino acids themselves undergo transamination and decarboxylation to give... 

There is little international agreement about the methods used for the analysis of hop resins. In Central Europe the classical Wollmer fractionation is often required. Elsewhere in Europe and in Britain the lead conductometric analysis for a-acids is the basis for commercial transactions. In the United States the spectrophotometric method for the estimation of a- and -acids is commonly employed. Modified methods are often required for extracts. The special methods required for isomerized extracts are discussed in Chapter 14. 

The light absorption of the hop resins depends on the pH of the solution and is accordingly measured under defined acidic or basic conditions. The absorption curves of humulone and lupulone are given in Fig. 13.4. From these curves regression equations were devised [30]. Optical density measure-... 

Aerial oxidation of most hop resins can occur by attack of oxygen either in the ring or on the isoprenyl (dimethylallyl) side chains. Oxidation in the ring can often be studied in hydrogenated derivatives with saturated side chains. 

---