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J Agric Food Chem

Title:		New cysteine-S-conjugate precursors of volatile sulfur compounds in bell peppers (Capsicum annuum L. cultivar)
Author(s):		Starkenmann C; Niclass Y;
Address:		"Corporate R&D Division, Firmenich SA, P.O. Box 239, CH-1211 Geneva 8, Switzerland. Christian.starkenmann@firmenich.com"
Journal Title:		J Agric Food Chem
Year:		2011
Volume:		20110304
Issue:		7
Page Number:		3358 - 3365
DOI:		10.1021/jf1042322
ISSN/ISBN:		1520-5118 (Electronic) 0021-8561 (Linking)
Abstract:		"The objective of this study was to verify whether the volatile organic sulfur compounds recently discovered in bell pepper (Capsicum annuum, L. cultivars), such as the mercapto-ketones: 4-sulfanyl-2-heptanone and 2-sulfanyl-4-heptanone, the mercapto-alcohols: 4-sulfanyl-2-heptanol and 2-sulfanyl-4-heptanol, and heptane-2,4-dithiol, originate from their corresponding cysteine-S-conjugates. Analysis of aqueous extracts of red and green bell pepper by ultraperformance liquid chromatography-mass spectrometry with electrospray ionization in the positive mode (UPLC-MS ESI(+)) displayed masses corresponding to the expected cysteine-S-conjugates. To confirm this observation, four cysteine-S-conjugates were prepared as authentic samples: S-(3-hydroxy-1-methylhexyl)-L-cysteine, S-(3-hydroxy-1-propylbutyl)-L-cysteine, S-(3-oxo-1-propylbutyl)-L-cysteine, and (2R,2'R)-3,3'-(4-hydroxyheptane-2,6-diyl)bis(sulfanediyl) bis(2-aminopropanoic acid). By comparison with the fragmentation patterns and retention times of synthetic mixtures of cysteine-S-conjugate diastereoisomers, the natural occurrence of cysteine conjugates was confirmed in bell peppers. In addition, the cysteine-S-conjugates from red and green bell pepper extracts were concentrated by ion exchange chromatography and the fractions incubated with a beta-lyase (apotryptophanase). The liberated thiols were concentrated by affinity chromatography, and their occurrence, detected by gas chromatography-mass spectrometry, confirmed our predictions. Moreover, 3-sulfanyl-1-hexanol was also detected and the occurrence of S-(1(2-hydroxyethyl)butyl)-L-cysteine confirmed. A quantitative estimation based on external calibration curves, established by UPLC-MS ESI(+) in selected reaction monitoring mode, showed that cysteine-S-conjugates were present at concentrations in the range of 1 to 100 mug/kg (+/-20%)"
Keywords:		Capsicum/*chemistry Cysteine/*analysis/chemistry/metabolism Fruit/*chemistry Gas Chromatography-Mass Spectrometry Sulfhydryl Compounds/metabolism Sulfur Compounds/*analysis Tryptophanase/metabolism Volatile Organic Compounds/*analysis;
Notes:		"MedlineStarkenmann, Christian Niclass, Yvan eng 2011/03/08 J Agric Food Chem. 2011 Apr 13; 59(7):3358-65. doi: 10.1021/jf1042322. Epub 2011 Mar 4"