The phytochemical profile of Macropiper excelsum (G.Forst.) Miq. subsp. excelsum (Piperaceae), a shrub which is widespread in New Zealand, was investigated by LC-MS-guided isolation and characterization via HR-ESI-TOF-MS and NMR spectroscopy. The isolated compounds were sensorily evaluated to identify their contribution to the overall taste of the crude extract with sweet, bitter, herbal and trigeminal impressions. Besides the known non-volatile Macropiper compounds, the lignans (+)-diayangambin and (+)-excelsin, four further excelsin isomers, (+)-diasesartemin, (+)-sesartemin, (+)-episesartemin A and B were newly characterized. Moreover, piperine and a number of piperine analogues as well as trans-pellitorine and two homologues, kalecide and (2E,4E)-tetradecadienoic acid N-isobutyl amide were identified in M. excelsum, some of them for the first time. Methyl(2E,4E)-7-(1,3-benzodioxol-5-yl)hepta-2,4-dienoate was identified and characterized for the first time in nature. Sensory analysis of the pure amides indicated that they contributed to the known chemesthetic effects of Macropiper leaves and fruits. Since the pungent piperine has been shown to affect glucose and fatty acid metabolism in vivo in previous studies, piperine itself and four of the isolated compounds, piperdardine, chingchengenamide A, dihydropiperlonguminine, and methyl(2E,4E)-7-(1,3-benzodioxol-5-yl)hepta-2,4-dienoate, were investigated regarding their effects on glucose and fatty acid uptake by enterocyte-like Caco-2 cells, in concentrations ranging from 0.1 to 100 μM. Piperdardine showed the most pronounced effect, with glucose uptake increased by 83 ± 18% at 100 μM compared to non-treated control cells. An amide group seems to be advantageous for glucose uptake stimulation, but not necessarily for fatty acid uptake-stimulating effects of piperine-related compounds.

Polyphenol-rich plant extracts have been shown to possess anti-inflammatory activity against oral pathogen-induced cytokine release in model systems of inflammation. Here, it was hypothesized that a flavanone-rich extract of E. angustifolium exhibits an anti-inflammatory potential against endotoxin-induced inflammatory response in human gingival fibroblasts (HGF-1). HGF-1 cells were stimulated with lipopolysaccharide from Porphyromonas gingivalis (pg-LPS) to release pro-inflammatory cytokines. Concentrations of interleukins IL-6 and IL-8 and macrophage chemoattractant protein-1 in the incubation media upon stimulation were determined by means of magnetic bead analysis. A crude ethanol/water extract of E. angustifolium (EE) was fractionated via gel permeation chromatography into a flavanone-rich fraction (FF) and an erionic acid-rich fraction (EF). Individual flavanones and erionic acids as well as EE, EF and FF were tested in the pg-LPS-stimulated HGF-1 cells for their anti-inflammatory potential. The E. angustifolium extract possessed anti-inflammatory potential in this model system, attenuating the pg-LPS-induced release of IL-6 by up to 52.0 ± 15.5%. Of the individual flavanones, eriodictyol and naringenin had the most pronounced effect. However, a mixture of the flavanones did not possess the same effect as the entire flavanoid fraction, indicating that other compounds may contribute to the anti-inflammatory potential of E. angustifolium. For the first time, an anti-inflammatory potential of E. angustifolium and containing erionic acids has been determined.

Chirality plays an important role in nature. In bio-recognition and transformation processes chirality acts as a basic selector for enzymes, microorganisms, plants and human beings. In 1848, Louis Pasteur was the first to report on the two stereoisomers of ammonium tartrate, and the famous British physicist Lord Kelvin concluded in 1883: "I call any geometrical figure or any groups of points chiral and say it has chirality if its image in a plane mirror, ideally realized cannot be brought to coincide with itself." Nowadays the principles of chirality are important for the investigation of natural products and xenobiotics as well. Multiple fields of research like pharma, plant physiology, feed, food and flavor chemistry are using enantioselective methods. Since chiral flavoring substances are sometimes characterized by different aroma and/or taste profiles as well as flavor intensities, enantiospecific evaluation of aroma compounds is key.

Sensory screening of a series of naturally occurring N-cinnamoyl derivatives of substituted phenethylamines revealed that rubemamine (9, from Chenopodium album) and rubescenamine (10, from Zanthoxylum rubsecens) elicit strong intrinsic umami taste in water at 50 and 10 ppm, respectively. Sensory tests in glutamate- and nucleotide-containing bases showed that the compounds influence the whole flavor profile of savory formulations. Both rubemamine (9) and rubescenamine (10) at 10-100 ppm dose-dependently positively modulated the umami taste of MSG (0.17-0.22%) up to threefold. Among the investigated amides, only rubemamine (9) and rubescenamine (10) are able to directly activate the TAS1R1-TAS1R3 umami taste receptor. Moreover, both compounds also synergistically modulated the activation of TAS1R1-TAS1R3 by MSG. Most remarkably, rubemamine (9) was able to further positively modulate the IMP-enhanced TAS1R1-TAS1R3 response to MSG ∼ 1.8-fold. Finally, armatamide (11), zanthosinamide (13), and dioxamine (14), which lack intrinsic umami taste in vivo and direct receptor response in vitro, also positively modulated receptor activation by MSG about twofold and the IMP-enhanced MSG-induced TAS1R1-TAS1R3 responses approximately by 50%. In sensory experiments, dioxamine (14) at 25 ppm in combination with 0.17% MSG exhibited a sensory equivalent to 0.37% MSG.

Sensory-guided analysis of an aqueous-ethanolic extract of Mondia whitei indicated sweetness enhancing effects of 2-hydroxy-4-methoxybenzaldehyde (HMBA). Further sensory tests confirmed these findings at low concentrations (0.5 mg/L). Higher concentrations did not show the desired effect, probably due to the strong coumarin-like flavor of HMBA. Similar to vanillin, the enhancement mainly results from a congruent flavor effect. Trials with nose clamps clearly reduced the observed effects. In a simple sugar reduced beverage application, however, HMBA was able to partly restore the sweetness of the beverage.

Some foods, beverages, and food ingredients show characteristic long-lasting aftertastes. The sweet, lingering taste of high intensity sweeteners or the astringency of tea catechins are typical examples. Epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea, causes a long-lasting astringency and bitterness. These sensations are mostly perceived as aversive and are only accepted in a few foods (e.g., tea and red wine). For the evaluation of the aftertaste of such constituents over a certain period of time, Intensity Variation Descriptive Methodology (IVDM) was used. The approach allows the measurement of different descriptors in parallel in one panel session. IVDM was evaluated concerning the inter- and intraindividual differences of panelists for bitterness and astringency of EGCG. Subsequently, the test method was used as a screening tool for the identification of potential modality-selective masking compounds. In particular, the intensity of the astringency of EGCG (750 mg kg(-1)) could be significantly lowered by 18-33% during the time course by adding the trigeminal-active compound trans-pellitorine (2E,4E-decadienoic acid N-isobutyl amide 1, 5 mg kg(-1)) without significantly affecting bitterness perception. Further, structurally related compounds were evaluated on EGCG to gain evidence for possible structure-activity relationships. A more polar derivative of 1, (2S)-2-[[(2E,4E)-deca-2,4-dienoyl]amino]propanoic acid 9, was also able to reduce the astringency of EGCG similar to trans-pellitorine but without showing the strong tingling effect.

Some foods, beverages, and food ingredients are characterized by their long-lasting aftertaste. Multiple time–intensity profiling (mTIP) was used to measure the aftertaste of compounds and mixtures over a certain period of time. Up to four different descriptors were recorded in parallel for a complex testing system, a sweetened green tea beverage. This method can also be used to evaluate possible masking effects. The bitterness and astringency of epigallocatechin gallate (EGCG) in particular was reduced by adding the “tingling” compound trans-pellitorine.