Berthold Weber

Identification of bisprenylated benzoic acid derivatives from yerba santa (Eriodictyon ssp.) using sensory-guided fractionation.

Due to certain off-flavor problems and lacking bitter masking effects with Yerba Santa (Eriodictyon angustifolium and E. californicum) extracts, which are also described as bitter, herbal, medicinal, phenolic, or astringent, methanolic extracts were fractionated and evaluated for their taste properties using a high temperature liquid chromatography (HTLC)-based approach. The taste-guided fractionation led to the identification of a series of novel bisprenylated benzoic acids (erionic acids A (1), B (2), C (3), D (4), E (5), and F (6) and eriolic acids A (7), B (8), C (9), and D (10), respectively), along with the known flavonoids eriodictyol, homoeriodictyol, hesperetin, and chrysoeriol. The new compounds were isolated in larger amounts for characterization from Narrow Leaf Yerba Santa (E. angustifolium) and California Yerba Santa (E. californicum), respectively, using fast centrifugal partition chromatography (FCPC) and HTLC. The structures were elucidated using one and two-dimensional NMR spectroscopy and high resolution mass spectrometry (HR-MS). For E. californicum, data regarding seasonal and climatic variation of the eriolic acid contents and of the flavonoids were collected. The flavor properties of some of the isolated new compounds were evaluated; they showed strong off-flavor characteristics, such as bitter, astringent, phenolic, or woody, and may contribute to the sensory effects observed for crude Yerba Santa extracts. Erionic acid C (3) was not only able to increase the absolute bitterness but also to extinguish the bitter masking effect of homoeriodictyol in a caffeine solution.

High-impact sulfur compounds: constitutional and configurational assignment of sulfur-containing heterocycles.

To unambiguously identify their structures and to evaluate their organoleptic properties, several constitutional und configurational isomers of dialkyl‐tetrathianes and dialkyl‐pentathiepanes were synthesized by two different synthetic protocols, and separated by preparative gas chromatography. Raman and NMR spectroscopy were used to differentiate between the constitutional 3,6‐dialkyl‐1,2,4,5‐tetrathiane and the 4,6‐dialkyl‐1,2,3,5‐tetrathiane isomers. Furthermore, cis‐ and trans‐isomers of 3,6‐dialkyl‐1,2,4,5‐tetrathianes were distinguished by temperature‐dependent NMR experiments. Static, quantum‐chemical simulations of the NMR spectra for these cis‐ and trans‐isomers were calculated in the gas layer in order to confirm our experimental assignments. In addition, the assignment of 4,7‐alkyl‐1,2,3,5,6‐pentathiepanes were deducted from their Raman spectra. Dialkyl‐tetrathianes and dialkyl‐pentathiepanes are interesting components to be used in flavor applications due to their unique olfactory impact and facets.

Extensive Study on the Minor Constituents of the Essential Oil of Eucalyptus dives Schau. Type

Abstract An oil of the piperitone type of Eucalyptus dives produced from trees cultivated in South Africa was analyzed by GC and GC/MS. Seventy-three constituents were characterized with piperitone ranging from 29.2% to 64.9%, depending on whether the oil was produced from dried or fresh leaves. Two novel constituents such as p-menth-5-en-2-one and p-menth-6-en-3-one were characterized as minor constituents of the oil; the former being found in nature for the first time.

The flavour chemistry of culinary Allium preparations

Abstract In culinary preparations cooked, roasted and fried Allium products play a major role in the taste and the aroma of the final product. In this study the correlation of various culinary preparation techniques such as cooking and frying and the resulting differences in the flavour chemistry (volatiles and non-volatiles) are demonstrated. Different preparation techniques performed on shallots, garlic and/or scallions influence the profile of volatiles and non-volatiles in culinary preparations significantly.