Characterization of Bitter-Tasting Oxylipins in Poppy Seeds (Papaver somniferum L.).

Activity-guided fractionation of poppy seed (Papaver somniferum L.) extracts and analysis of fatty acid oxidation model experiments, followed by liquid chromatography time-of-flight mass spectrometry, tandem mass spectrometry, and one-/two-dimensional nuclear magnetic resonance experiments, revealed the chemical structures of five bitter-tasting fatty acids (1-5), three monoglycerides (6-8), six C18-lipidoxidation products (9-14), and four lipid oxidation degradation products (15 and 17-19) as well as two previously unreported monoglyceride oxidation degradation products, namely, 9-(2',3'-dihydroxypropyloxy)-9-oxononaic acid (1-azeloyl-rac-glycerol, 16) and 1-(2',3'-dihydroxypropyl)-8-(5″-oxo-2″,5″-dihydrofruan-2″-yl)-octonoate (1-ODFO-rac-glycerol, 20). Sensory studies exhibited low bitter taste threshold concentrations between 0.08 and 0.29 mmol/L, particularly for the higher oxidated C18-fatty acids trihydroxyoctadecenoic acid (THOE, 12), 12,13-dihydroxy-9-oxo-10-octadecenoic acid (12,13-diOH-9-oxo, 13), and 9,10-dihydroxy-13-oxo-11-octadecenoic acid (9,10-diOH-13-oxo, 14) as well as for the lipidoxidation degradation products 4-hydroxy-2-noneic acid (4-HNA, 17), 4-hydroxy-2-docecendienoic acid (HDdiA, 18), and 8-(5'-oxo-2',5'-dihydrofuran-2'-yl)-octanoic acid (ODFO, 20).

Structure-Pungency Relationships and TRP Channel Activation of Drimane Sesquiterpenes in Tasmanian Pepper (Tasmannia lanceolata).

Sensory-guided fractionation of extracts of Tasmanian pepper berries revealed 20 drimane sesquiterpens, among which polygodial, warburganal, and 1ß-acetoxy-9-deoxy-isomuzigadial exhibited the lowest pungency threshold concentrations on the tongue surface (0.6-2.8 nmol/cm2) and elicited a dose-dependent calcium influx into mTRPA1 expressing CHO cells with the lowest EC50 values (4.5 ± 1.0 to 16.7 ± 7.5 µmol/L) and a good correlation to oral pungency thresholds (R2 = 0.986, linear regression). Calcium imaging assays demonstrated these chemosensates to induce a calcium influx into cultured trigeminal neurons prepared from wildtype (TRPA1+/+) mice, whereas no calcium influx was observed in neurons from TRPA1 knockout mice (TRPA1-/-), thus confirming the α,ß-unsaturated 1,4-dialdehyde structure to be the required structural motif for a low oral puncency thresholds and activation of the Transient Receptor Potential Channel A1 (TRPA1). Time-resolved NMR experiments confirmed the pungency mediating mechanism for electrophilic drimane sesquiterpene dialdehydes to be different from that found for other electrophilic pungent agents like isothiocyanates, which have been shown to undergo a covalent binding with cysteine residues in TRPA1. Instead, the high-impact chemosensates polygodial, warburganal, and 1ß-acetoxy-9-deoxy-isomuzigadial showed immediate reactivity with the ε-amino group of lysine side chains to give pyrrole-type conjugates, thus showing evidence for TRPA1 activation by covalent lysine modification.