Enantiomeric ratios of 2-methylbutanoic acid and its methyl ester: Elucidation of novel biogenetic pathways towards (R)-methyl 2-methylbutanoate in a beverage fermented with shiitake
| Autor: | Marco A. Fraatz, Andreas Hammer, Marina Rigling, Yanyan Zhang, Holger Zorn, Florian Birk |
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| Rok vydání: | 2018 |
| Předmět: |
Shiitake Mushrooms
Tiglic acid L-Isoleucine 01 natural sciences Aldehyde Gas Chromatography-Mass Spectrometry Analytical Chemistry Beverages chemistry.chemical_compound 0404 agricultural biotechnology Bioreactors Hemiterpenes Organic chemistry Isoleucine Flavor Solid Phase Microextraction chemistry.chemical_classification 010401 analytical chemistry Substrate (chemistry) Esters Stereoisomerism 04 agricultural and veterinary sciences General Medicine 040401 food science 0104 chemical sciences Butyrates Kinetics chemistry Odor Crotonates Fermentation Enantiomer Food Science |
| Zdroj: | Food chemistry. 266 |
| ISSN: | 1873-7072 |
| Popis: | Up to 35% of (R)-methyl 2-methylbutanoate (M2MB) was observed in a beverage fermented with shiitake. As M2MB naturally occurs typically in high excesses of the (S)-enantiomer, the origin of the (R)-ester was elucidated by stable isotope labeled precursor-feeding studies. (R)-2-Methylbutanoic acid was identified as the main precursor in the substrate wort. Trace amounts of (R)-M2MB were produced by transformation of unsaturated secondary metabolites (tiglic aldehyde and tiglic acid) derived from l-isoleucine. Surprisingly, shiitake esterified (R)-2-methylbutanoic acid faster to (R)-M2MB than the corresponding (S)-enantiomer. Concurrently, spontaneous non-enantioselective degradation of M2MB occurred in shiitake. This explains diverse enantiomeric ratios of M2MB and different enantiomeric ratios of 2-methylbutanoic acid and M2MB in the beverage. As the odor threshold values of (R)-and (S)-M2MB differ significantly, these findings are of high relevance for the overall flavor of the fermented beverage and elucidate the discrepancy of enantiomeric ratios of 2-alkyl-branched acids and esters reported in nature. |
| Databáze: | OpenAIRE |
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