Trace amines such as p- tyramine, p- octopamine and p- synephrine are found in low concentrations in animals and plants. Consumption of pre-workout supplements containing these plant-derived amines has been associated with cardiovascular side effects. The aim of this study was to determine the mechanisms of action of these trace amines on porcine isolated coronary and mesenteric arteries. Noradrenaline caused contraction of mesenteric arteries and relaxation of coronary arteries. In both tissues, all three trace amines induced contractions with similar potencies and responses were unaffected by the β-adrenoceptor antagonist propranolol (1 µM), the nitric oxide synthase inhibitor L-NNA (100 µM), or the TAAR-1 antagonist, EPPTB (100 nM). However, the contractile responses of mesenteric arteries, but not coronary arteries, were significantly reduced by depletion of endogenous noradrenaline. Mesenteric responses to all three amines were abolished in the presence of prazosin (1 µM) whereas residual contractile responses remained in the coronary artery which were inhibited by a high concentration (100 µM) of EPPTB. The results suggest complex responses of the coronary artery to the trace amines, with activity at α 1 -adrenoceptors and potentially TAARs other than TAAR-1. In contrast the actions of the amines on the mesenteric artery appeared to involve indirect sympathomimetic actions and direct actions on α 1 -adrenoceptors.

No abstract

Multi‐ingredient pre‐workout supplements (MIPS) contain Citrus aurantium as a source of bioactive amines such as p‐synephrine, but concerns regarding the authenticity of ingredients in some supplements as well as adverse effects from consumption have been raised. R‐(−)‐Synephrine is the predominant enantiomer in Citrus aurantium extracts while synthetic preparations are often racemic. The aims of this study were to develop a screening method to determine the ratio of synephrine enantiomers in pre‐workout supplements listing Citrus aurantium and to assess the ingredient authenticity by directly comparing their ratios to that found in Citrus aurantium standardised reference materials (SRMs). Quantification of enantiomers in the supplements and SRMs was achieved using a validated, high‐performance liquid chromatography‐single quadrupole mass spectrometry (HPLC‐UV‐QDa) direct enantioseparation method with a cellobiohydrolase (CBH) column (100 × 4.0 mm, 5 μM) and UV detection at 225 nm. Citrus aurantium SRMs were found to have an average enantiomeric ratio of 94:6 (R:S) with total synephrine ranging from 5.7 to 90.2 mg/g. Within the pilot sample of pre‐workout supplements tested, only 42% (5/12) had enantiomeric ratios consistent with the SRMs with total synephrine ranging from 0.03 to 91.2 mg/g. For the remaining supplements, four had racemic ratios of synephrine (0.14 to 5.4 mg/g), two lacked any detectable levels of synephrine, and one had solely the S‐(+)‐enantiomer (0.15 mg/g). These results bring the authenticity of labelling of some pre‐workout supplements into question and highlight the need for more stringent labelling regulations and testing for dietary supplements.

No abstract

An efficient synthesis of the O-linked glycosylamino acid Fmoc–l-Ser((Ac)3–β-d-GlcNAc)-OH building block is described. The utility of the method was demonstrated with direct solid-phase O-glycosylation of the hydroxyl group on the amino acid (Ser) side chain of a human α-A crystallin-derived peptide (AIPVSREEK) in nearly quantitative glycosylation yield.