2-Aminoacetophenone Is the Main Volatile Phase I Skatole Metabolite in Pietrain × Baden-Württemberg Hybrid Type Boars

An overlooked compound contributing to boar taint and consumer rejection of meat products: 2-Aminoacetophenone

Mainly skatole and androstenone have so far been considered causative for boar taint. Using a mixed methods approach it is shown herein that 2-aminoacetophenone (AAP) affects human perception of pork, too. We explored the importance of AAP in four trials: (1) chemical analyses of 221 fat samples from boar carcasses revealed that AAP occurs, on average, in similar quantities as skatole while the levels of androstenone being four-fold. (2) ranking tests with mixtures of androstenone and/or skatole with AAP presented on smell strips to trained sensory assessors showed that AAP amplifies boar odour. In order to study AAP's importance in meat products, four experimental variants of Lyon type sausage were then produced: a control, a product with added skatole (0.075 μg/g fat tissue), with added AAP (0.075 μg/g fat tissue), and with addition of both compounds. (3) results of a consumer discrimination test panel (n = 71) showed that, when added to a sausage system, APP causes a sensory difference of similar size as skatole while the methodology chosen affects the effect size: tetrad tests proved to be more sensitive than duo trio difference tests, in the tetrad test a sensory difference expressed as d' (d-prime) of 1.0 was reached. (4) a hedonic consumer test (n = 121) finally revealed that APP decreased consumer liking of the APP-spiked sausage - even to a stronger extent than skatole. APP caused significant drops in smell, taste, mouth-feel, after-taste and overall liking in Lyoner. Overall the findings suggest that, in the context of pork meat, AAP is of similar olfactory importance as skatole.

Chaihu-Shugan-San Reinforces CYP3A4 Expression via Pregnane X Receptor in Depressive Treatment of Liver-Qi Stagnation Syndrome

Backgrounds. Chaihu-Shugan-San (CSS) is a classic traditional Chinese herbal prescription for treating depression. However, the underlying mechanism of the Chinese syndrome-specific efficacy of CSS is poorly understood. Aim of the Study. From traditional Chinese medicine and pharmacogenetics perspectives, the present study aimed to investigate the antidepressant effects of CSS on a mouse model of Liver-Qi Stagnation (LQS) syndrome and its underlying mechanisms. Methods and Materials. We used two main mouse models of depressive syndromes in the study, including LQS and liver stagnation and spleen deficiency (LSSD) syndrome. Tail suspension and forced swimming tests were used to evaluate the effects of CSS on animal behaviour. The expression level of the CYP450 enzyme from liver microsomes was analysed by western blot (WB) analysis and quantitative real-time polymerase chain reaction (qRT-PCR). More specifically, we analysed the key compounds of CSS that are responsible for CYP450 regulation via bioinformatics. Ultimately, luciferase assays were employed to confirm the prediction in vitro. Results. CSS remarkably reduced the immobile time in LQS rather than in LSSD mice. Although CSS significantly upregulated CYP2C9 in mice with both syndromes, activated translation of CYP3A4 induced by CSS was only observed in the LQS group. Bioinformatics analysis revealed that the unique regulation of CYP3A4 was responsible for the effects of glycyrrhetinic acid (GA) from CSS. Further luciferase assays confirmed the enhancement of CYP3A4 expression via the pregnane X receptor (PXR) pathway in vitro. Conclusions. CSS specifically upregulates the translation of CYP3A4 via the PXR pathway in depressed LQS mice. GA, a bioactive compound that originates from CSS, contributes to this activation. This work provides novel insight into Chinese syndrome-based therapy for depression.

End-product inhibition of skatole-metabolising enzymes CYP1A, CYP2A19 and CYP2E1 in porcine and piscine hepatic microsomes

The hepatic cytochrome p450 enzymes 1 A, 2A19 and 2E1 is very important for the elimination of skatole from the body of pigs. Impaired skatole metabolism, results in skatole accumulation, which give rise to off flavor of the meat. Several metabolites of skatole has been identified, however the role of these metabolites in the inhibition of the skatole metabolizing enzymes are not documented. Using microsomes from pigs and fish, we determined the ability of several skatole metabolites to inhibit CYP1 A, CYP2A19 and CYP2E1 dependent activity. Our results show that 2-aminoacetophenone is an inhibitor of porcine CYP2A19 and CYP2E1 activity, but not the piscine orthologues. In conclusion, there is species specific differences in the inhibition of CYP1 A and CYP2A19 dependent metabolism of probe substrates. This is relevant to the evaluation of different model systems and to the reduction of off flavor of meat.

Comparative Aroma Extract Dilution Analysis (cAEDA) of Fat from Tainted Boars, Castrated Male Pigs, and Female Pigs

The aroma profile of porcine fat from tainted boars, female pigs, and castrated male pigs was investigated by application of comparative aroma extract dilution analysis (cAEDA) on a SAFE distillate of volatiles prepared from porcine back fat samples. The AEDA resulted in a total of 16 aroma active compounds for boar fat with flavor dilution (FD) factors ranging from 2 to 2048, whereas 12 aroma active compounds were found in fat of female pigs and 14 in fat of castrated male pigs, both with FD factors ranging from 2 to 32. Odor activity values (OAVs) of key components for each fat were identified: In boar fat androstenone, skatole, indole, and 2-aminoacetophenone showed highest OAVs, whereas 2,5-dimethylpyrazine, 2,4-decadienal, and δ-decalactone showed highest OAVs in fat of female pigs. Fat of castrated male pigs showed highest OAVs for skatole, indole, 1-octen-3-ol and methional. Finally, the off-flavor attributes of boar fat were successfully simulated by a recombinant of all odorants at their natural concentration level in deodorized sunflower oil.

Deuterium-Labeling Studies Reveal the Mechanism of Cytochrome P450-Catalyzed Formation of 2-Aminoacetophenone from 3-Methylindole (Skatole) in Porcine Liver Microsomes

2-Aminoacetophenone, a product of the hepatic 3-methylindole (skatole) clearance in pigs, contributes to the specific aroma of fat from tainted boar meat. Surprisingly, high formation rates for 2-aminoacetophenone from skatole in microsomal preparations from Pietrain × Baden-Württemberg hybrid type boars have been previously demonstrated, but the mechanism of this cytochrome P450-mediated reaction remained unknown. Therefore, microsomal fractions from boars were incubated with deuterium-labeled skatole and with possible reaction intermediates. 3-Methyloxindole and 3-hydroxy-3-methyloxindole were identified as degradation products of skatole en route to 2-aminoacetophenone. Additionally, the labeling studies provided further evidence for a cytochrome P450-mediated lyase reaction that leads to the cleavage of the indole heterocyclic ring system in 3-hydroxy-3-methyloxindole and demonstrated the involvement of several cytochrome P450-isoforms by employing isotopically sensitive branching experiments.