Myrrh and opopanax has been used throughout history in incense and as a perfume. Since Bible times it has been used for the treatment of wounds. The first attempts to identify content compounds were almost 100 years ago. In this review we discuss the present state of knowledge in the chemistry of substances of Commiphora spp.

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Myrrh--Commiphora chemistry.

Analysis of single cornicle droplets from six species of aphid showed the presence of volatile components in addition to (E)-β-farnesene. Compounds identified included (Z,E)-α- and (E,E)-α-farnesene forMyzus persicae and α- and β-pinene forMegoura viciae. WithMegoura viciae, (−)-α-pinene was most important for alarm activity. The major component of the alarm pheromone ofPhorodon humuli was (E)-β-farnesene even though farnesenes are present in the summer hostHumulus lupulus.

Composition of aphid alarm pheromones

The hop cones of the female plant of the common hop species Humulus lupulus L. are grown almost exclusively for the brewing industry. Only the cones of the female plants are able to secrete the fine yellow resinous powder (i.e. lupulin glands). It is in these lupulin glands that the main brewing principles of hops, the resins and essential oils, are synthesized and accumulated. Hops are of interest to the brewer since they impart the typical bitter taste and aroma to beer and are responsible for the perceived hop character. In addition to the comfortable bitterness and the refreshing hoppy aroma delivered by hops, the hop acids also contribute to the overall microbial stability of beer. Another benefit of the hop resins is that they help enhance and stabilize beer foam and promote foam lacing. In an attempt to understand these contributions, the very complex nature of the chemical composition of hops is reviewed. First, a general overview of the hop chemistry and nomenclature is presented. Then, the different hop resins found in the lupulin glands of the hop cones are discussed in detail. The major hop bitter acids (α- and β-acids) and the latest findings on the absolute configuration of the cis and trans iso-α-acids are discussed. Special attention is given to the hard resins; the known δ-resin is reviewed and the e-resin is introduced. Recent data on the bittering potential and the antimicrobial properties of both hard resin fractions are disclosed. Attention is also given to the numerous essential oil constituents as well as their contributions to beer aroma. In addition to the aroma contribution of the well-known essential oil compounds, a number of recently identified sulfur compounds and their impact on beer aroma are reviewed. The hop polyphenols and their potential health benefits are also addressed. Subsequently, the importance of hops in brewing is examined and the contributions of hops to beer quality are explained. Finally, the beer and hop market of the last century, as well as the new trends in brewing, are discussed in detail. Hop research is an ever growing field of central importance to the brewing industry, even in areas that are not traditionally associated with hops and brewing. This article attempts to give a general overview of the different areas of hop research while assessing the latest advances in hop science and their impact on brewing. Copyright © 2014 The Institute of Brewing & Distilling

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jib.160

Humulus lupulus – a story that begs to be told. A review

The urinary volatiles from dominant and subordinate male mice were chromatographically compared, both immediately and seven days after dominant-subordinate relationships between pairs were formed. Statistical comparison of the peak areas of volatile constituents present in male urine revealed that 16 urinary compounds exhibited substantial concentration differences depending upon social status of the animals. Urinary dihydrofurans, ketones, and acetates exhibited a significant, long-term (seven-day) decrease in the urine of subordinates when compared to control and dominant males. Two sesquiterpenic compounds, α- and β-farnesene, were elevated only in the dominant urine one week after dominance was established. 2-(sec-Butyl)-4,5-dihydrothiazole was found in higher concentration in bladder or excreted urine of dominant males when compared to subordinates. Of the 16 compounds subjected to statistical analysis, four exhibited hormonal dependency: α- and β-farnesene, dehydro-exo-brevicomin, and 2-(sec-butyl)-4,5-dihydrothiazole. Neither dehydro-exo-brevicomin nor 2-(sec-butyl)-4,5-dihydrothiazole was present in the urine of immature and castrated males. Testosterone treatment restores their presence in male urine. Also, α- and β-farnesene were absent in the urine of immature males and significantly reduced in the urine of castrated males. The absence of α- and β-farnesene in bladder urine suggests that one of the sex-accessory glands may be the site of their origin.

Pattern of volatile compounds in dominant and subordinate male mouse urine.

Knoevenagel's first papers in this field were concerned with the condensation of formaldehyde with diethyl malonate and with ethyl benzoylacetate. The catalyst was ethylamine. A number of other aldehydes were reported to condense similarly with diethyl malonate, ethyl benzoylacetate, ethyl benzoylpyruvate, and acetylacetone under the influence of various primary and secondary amines. In 1896, Knoevenagel reported benzaldehyde with ethyl aceoacetate condensed at room temperature in the presence of piperdine to give a bis compound, but that when the reaction was run in a freezing mixture, the product was acetoacetate. For the purposes of this chapter, the Knoevenagel condensation is defined as the reaction between an aldehyde or ketone or any compound having an active methylene group, brought about by an organic base or ammonia and their salts.


Keywords:

Knoevenagel condensations;
decarboxylation;
malonic acid;
active methylene component;
stereochemical aspects;
cyanoacetic acid;
ketones;
derivatives. caatalysts;
experimental conditions

J. Plíva

Papers

On terpenes. XIII. On the sesquiterpenes from the essential oil of hops

On terpenes. LXXXVIII. The structure of germacrone, the crystalline constituent of Bulgarian zdravets oil

On terpenes. XLIII. Infrared investigations of terpenes. IV.

On terpenes. XLI. The sesquiterpenes of ginger oil

On terpenes. XLVI. Sesquiterpenic hydrocarbons from oil of sweet flag