Quercetin 3,3',4'-tri-O-beta-D-glucopyranosides from leaves of Eruca sativa (Mill.).

Three new quercetin 3,3',4'-tri-O-beta-D-glucopyranosides isolated from leaves of Eruca sativa (Mill.) were identified as quercetin 3,3',4'-tri-O-beta-D-glucopyranoside, quercetin 3'-(6-sinapoyl-O-beta-D-glucopyranosyl)-3,4'-di-O-beta-D-glucopyranoside and quercetin 3-(2-sinapoyl-O-beta-D-glucopyranosyl)-3'-(6-sinapoyl-O-beta-D-glucopyranosyl)-4'-O-beta-D-glucopyranoside. The structures were established by one- and two-dimensional 1H and 13C NMR spectra as well as b

Flavor authenticity studies by (2)h/(1)h ratio determination using on-line gas chromatography pyrolysis isotope ratio mass spectrometry.

Based on (2)H/(1)H ratio measurements of commercial synthetic and "natural" references, the recently developed on-line gas chromatography pyrolysis isotope ratio mass spectrometry (HRGC-P-IRMS) technique was used to determine the delta(2)H(SMOW) values of the flavor compounds decanal, linalool, and linalyl acetate, as well as those of E-2-hexenal and E-2-hexenol in foods and essential oils. In preceding model studies, the influence of sample preparation steps (simultaneous distillation extraction, SDE; solvent extraction, SE; liquid liquid extraction, LLE) on the delta(2)H values was found to be negligible. For decanal, the typical (2)H abundance, with higher content of (2)H for synthetic material (delta(2)H(SMOW) from -90 to -156 per thousand) and lower (2)H content for natural references (delta(2)H(SMOW) from -138 to -262 per thousand) was observed. Although the delta(2)H data recorded for linalool did not allow one to distinguish between synthetic (delta(2)H(SMOW) from -207 to -301 per thousand) and natural (delta(2)H(SMOW) from -234 to -333 per thousand) materials, the situation was somewhat more encouraging for linalyl acetate; delta(2)H(SMOW) values from -199 to -239 per thousand and from -213 to -333 per thousand were found for synthetic and natural samples, respectively. E-2-Hexenal and E-2-hexenol showed clear-cut origin-dependent differences in their (2)H/(1)H ratios; that is, delta(2)H(SMOW) values from -14 to -109 per thousand and from -263 to -415 per thousand as well as from -41 to -131 per thousand and from -238 to -348 per thousand were recorded for products from synthetic and natural origins, respectively.

Metabolism of ethyl tiglate in apple fruits leads to the formation of small amounts of (R)-ethyl 2-methylbutanoate.

(S)-Ethyl 2-methylbutanoate is an important aroma compound in apples and serves as an indicator for genuineness of apple products due to its high optical purity of greater than 98% enantiomeric excess [T. Koenig and P. Schreier, Zeitsch. Lebensm.-Unters. Forsch. A, 1999, 208, 130-133; K. Schumacher et al., J. Agric. Food Chem., 1998, 46, 4496-4500]. The origin of minor amounts of (R)-ethyl 2-methylbutanoate is unknown as naturally occurring (+)-isoleucine, the proposed precursor of (S)-ethyl 2-methylbutanoate is enantiomerically pure. Since ethyl (E)-2-methyl-2-butenoate (ethyl tiglate) was recently discovered as a natural apple constituent and hydrogenation activity in apples was demonstrated we proposed ethyl tiglate as a precursor of (R)-ethyl 2-methylbutanoate. D4-3,4,4,4-ethyl tiglate was synthesized and was injected into ripe apple fruits (cv. Golden Delicious, Red Delicious and Granny Smith). After 3, 6, and 12 days apple volatiles were isolated by solid phase extraction on XAD-2 and the metabolites formed from D4-3,4,4,4-ethyl tiglate were analyzed by capillary gas chromatography-mass spectrometry (GC-MS). Ethyl 2-methylbutanoate, 2-methylbutyl acetate, 2-methylbutanol, and 2-methylbutanoic acid were identified as major transformation products. Chiral evaluation of the metabolites by multidimensional GC-MS revealed enantiomeric excesses ranging from 43% (S) to 30% (R) depending on the apple cultivar, sampling date and metabolite. The data show for the first time that the natural apple constituent ethyl tiglate can serve as a source for (R)-2-methylbutanol derivatives.

A new one-step strategy for the stereochemical assignment of acyclic 2- and 3-sulfanyl-1-alkanols using the CD exciton chirality method.

A new one-step strategy is described for the stereochemical assignment of acyclic 2- and 3-sulfanyl-1-alkanols using the CD exciton chirality method. Using the 9-anthroate chromophore for the derivatization of both functional groups, the resulting bisignate CD curves unequivocally allow the determination of the stereochemistry from a single CD measurement. The usefulness of the new method is demonstrated using synthesized optically pure 3-sulfanyl-1-hexanols and 2-sulfanyl-1-hexanols as model compounds. The developed microscale method is also useful for the stereochemical assignment of 1,2- and 1,3-diols. To our knowledge this is the first application of the CD exciton chirality method to acyclic 2- and 3-sulfanyl-1-alkanols.