A Comparison of Quantitative Composition and Bioactivity of Oils Derived from Seven North American Varieties of Hops (Humulus lupulus L.)

Abstract

Seven commercial hop (Humulus lupulus L.) oils originating from a selection of North American hop varieties (Amarillo, Azacca, Cascade, Centennial, Chinook, Saaz, and Ahhhroma) and six homemade hop oils hydrodistilled from the same commercial hop pellets (except Ahhhroma) were compared. Seven terpenes regarded as hop oil markers (i.e., α-pinene, β-pinene, β-myrcene, β-ocimene, limonene, β-caryophyllene, and α-humulene) and methyl heptanoate were identified and quantified by GC–MS and GC-FID. The antioxidant potential of the commercial hop oil samples was evaluated using electron paramagnetic resonance (EPR) spectroscopy, while their components’ antibacterial (against Aliivibrio fischeri) and enzyme (α-glucosidase and lipase) inhibition activities were screened using high-performance thin-layer chromatography (HPTLC)-based assays. A distinct feature of five of the commercial hop oils (except Saaz and Ahhhroma) was relatively high contents of β-myrcene (between 4.21 and 6.40 µg mg−1 hop oil). Azacca, Cascade, and Centennial hydrodistilled oils had perceptibly higher contents of β-caryophyllene than the rest, and most of them (except Chinook) contained relatively high amounts of α-humulene. Differences between the terpene profiles of the commercial and homemade hydrodistilled hop oils suggested that the commercial hop oils were derived from hop cones in a process different from hydrodistillation. The oils showed relatively low antioxidant potential, comparable to that of popular beers and white wines. The highest antioxidant potential was observed in Ahhhroma oil, while it was very low in Centennial oil, and no antioxidant potential was observed in Cascade and Saaz oils. The developed streamlined workflow, including parallel HPTLC-directed bioassays and HPTLC—TLC–MS Interface—SPME–GC–MS, enabled the identification of β-myrcene, dimyrcenes, β-farnesene, and 2-methylbutyl isobutyrate as anti-obesity compounds and β-farnesene, β-myrcene, and 2-methylbutyl isobutyrate as weak antibacterial hop oil components.

Comprehensive Two-Dimensional Gas Chromatography–Mass Spectrometry as a Tool for the Untargeted Study of Hop and Their Metabolites

“…In the results of Yan et al, the essential oil fraction of CASC was hydrodistilled and as a result also displayed the presence of geraniol and perillene, proving certain similarities. When compared to the composition of humulene (36.44%) and β-myrcene (5.93%) (noting limitations due to the SPME sampling), this paper shows a contrary behaviour compared to the literature [34,55,58], where the concentration of βmyrcene is higher than humulene, which is explained as a distinct sample with a probable cause of low content of β-myrcene and high content of humulene related to the ripening period, more specifically an early harvest or a not-well-ripe hop [4,54]. Characterising some of the compounds, attention may be called to the unique compounds in each of the samples with the presence of clusters close to their respective red triangles shown in Figure 5.…”

“…This shows that CASC has a relation with the auto-oxidation of myrcene [56,57] by the formation of geraniol, an important floral odorant in the hop essential oil, as the presence of camphene and linalool oxide in the two isomeric forms, related to the "European hop aroma" [17,57]. The hop CASC is widely studied in the literature, as in the GC×GC-TOFMS study from Yan et al [34], and by GC-MS from other studies [55]. In the results of Yan et al, the essential oil fraction of CASC was hydrodistilled and as a result also displayed the presence of geraniol and perillene, proving certain similarities.…”

“…This shows a significant connection between AZAC and the ketone formed in its metabolism. Regarding reports from the literature [55], the hop AZAC was studied by GC-MS and a method for the fraction of hydrodistilled essential oil followed by HS-SPME. This study also showed a high concentration of caryophyllene and a high percentage of humulene as reported by results in Table 3.…”

“…This shows a significant connection between AZAC and the ketone formed in its metabolism. Regarding reports from the literature [55], the hop AZAC was studied by GC-MS and a method for the fraction of hydrodistilled essential oil followed by HS-SPME. This study Regarding ENIG, three classes were significant: monoterpene hydrocarbons comprising β-myrcene (22), β-ocimene (35), and trans-β-ocimene (36), the two sesquiterpene hydrocarbons (E)-β-farnesene (107) and β-eudesmene (117), and the esters isobutyl 2-methylbutanoate (25) and 2-methylbutyl octanoate (106).…”