Analysis of eleven phenolic compounds including novel p-coumaroyl derivatives in lettuce (Lactuca sativa L.) by ultra-high-performance liquid chromatography with photodiode array and mass spectrometry detection.

INTRODUCTION Lettuce is a widely consumed vegetable and a good source of phenolic compounds. Several factors (genetic, agronomical and environmental) can influence the lettuce composition; their effects are not completely defined and more studies are needed on this topic. OBJECTIVE To develop an improved ultra-high-performance liquid chromatography (UHPLC) method to quantify the main target intact phenolic compounds in lettuce. METHODOLOGY UHPLC identification of the compounds was supported by PAD spectra and MS(n) analyses. Quantification was carried out by PAD, by creating matrix-matched calibration curves at the specific wavelength for each compound. RESULTS Sample pretreatment was simplified, with neither purification nor hydrolysis steps. Chromatographic conditions were chosen to minimise matrix interferences and to give a suitable separation of the major phenolic compounds within 27 min. The method allowed the quantification of 11 intact phenolic compounds in Romaine lettuces, including phenolic acids (caffeoyl and p-coumaroyl esters) and flavonoids (quercetin glycosides). Four p-coumaroyl esters were tentatively identified and quantified for the first time in lettuce. CONCLUSION The main intact phenolic compounds, including four novel p-coumaroyl esters, were simultaneously quantified in lettuce with optimal performances and a reduced total time of analysis. These findings make headway in the understanding of the lettuce phytochemicals with potential nutritional relevance.

[1]  J. Mazzeo,et al.  The application of small porous particles, high temperatures, and high pressures to generate very high resolution LC and LC/MS separations. , 2007, Journal of separation science.

[2]  V. Gökmen,et al.  Effect of various anti-browning agents on phenolic compounds profile of fresh lettuce (L. sativa) , 2009 .

[3]  B. Gallo,et al.  Optimization and validation of a methodology based on solvent extraction and liquid chromatography for the simultaneous determination of several polyphenolic families in fruit juices. , 2007, Journal of chromatography. A.

[4]  Federico Ferreres,et al.  Characterisation of polyphenols and antioxidant properties of five lettuce varieties and escarole. , 2008, Food chemistry.

[5]  A. Romani,et al.  Polyphenol content and antiradical activity of Cichorium intybus L. from biodynamic and conventional farming , 2009 .

[6]  Liliana Jiménez,et al.  Polyphenols: food sources and bioavailability. , 2004, The American journal of clinical nutrition.

[7]  P. Andrade,et al.  Phenolic profile of hazelnut (Corylus Avellana L.) leaves cultivars grown in Portugal , 2005, Natural product research.

[8]  Alan Crozier,et al.  Quantitative analysis of the flavonoid content of commercial tomatoes , 1997 .

[9]  A. Crozier,et al.  Total phenol, flavonoid, proanthocyanidin and vitamin C levels and antioxidant activities of Mauritian vegetables , 2004 .

[10]  M. Clifford,et al.  Discriminating between the six isomers of dicaffeoylquinic acid by LC-MS(n). , 2005, Journal of agricultural and food chemistry.

[11]  Michael N. Clifford,et al.  Chlorogenic acids and other cinnamates – nature, occurrence and dietary burden , 1999 .

[12]  V. Fogliano,et al.  Polyphenol composition and qualitative characteristics of fresh-cut lettuce in relation to cultivar, mulching, and storage , 2007 .

[13]  K. Robards,et al.  Analytical chemistry of fruit bioflavonoids. A review. , 1997 .

[14]  Portland Press Ltd IUPAC Commission on the Nomenclature of Organic Chemistry (CNOC) and IUPAC-IUB Commission on Biochemical Nomenclature (CBN). Nomenclature of cyclitols. Recommendations, 1973. , 1976, The Biochemical journal.

[15]  J. Espín,et al.  Varietal differences among the polyphenol profiles of seven table grape cultivars studied by LC-DAD-MS-MS. , 2002, Journal of agricultural and food chemistry.

[16]  R. Carle,et al.  Effect of different washing procedures on phenolic metabolism of shredded, packaged iceberg lettuce during storage. , 2004, Journal of agricultural and food chemistry.

[17]  F. Tomás-Barberán,et al.  Lettuce and chicory byproducts as a source of antioxidant phenolic extracts. , 2004, Journal of agricultural and food chemistry.

[18]  M. Castellari,et al.  Analysis of wine phenolics by high-performance liquid chromatography using a monolithic type column. , 2002, Journal of chromatography. A.

[19]  E. van Nood,et al.  Flavonoids: a review of probable mechanisms of action and potential applications. , 2001, The American journal of clinical nutrition.

[20]  M. Serafini,et al.  Effect of acute ingestion of fresh and stored lettuce (Lactuca sativa) on plasma total antioxidant capacity and antioxidant levels in human subjects. , 2002, The British journal of nutrition.

[21]  M. Clifford,et al.  Dietary phenolics: chemistry, bioavailability and effects on health. , 2009, Natural product reports.

[22]  P. Solich,et al.  Rapid qualitative and quantitative ultra high performance liquid chromatography method for simultaneous analysis of twenty nine common phenolic compounds of various structures. , 2010, Talanta.

[23]  Antonio Cimato,et al.  Polyphenols in greenhouse and open-air-grown lettuce , 2002 .

[24]  Raoul J. Bino,et al.  A Liquid Chromatography-Mass Spectrometry-Based Metabolome Database for Tomato1 , 2006, Plant Physiology.

[25]  M. Castellari,et al.  Simultaneous evaluation of intact glucosinolates and phenolic compounds by UPLC-DAD-MS/MS in Brassica oleracea L. var. botrytis , 2010 .

[26]  R. Welti,et al.  Phytochemical phenolics in organically grown vegetables. , 2005, Molecular nutrition & food research.

[27]  M. Clifford,et al.  Hierarchical scheme for LC-MSn identification of chlorogenic acids. , 2003, Journal of agricultural and food chemistry.

[28]  J. Lovegrove,et al.  Changes in the flavonoid and phenolic acid contents and antioxidant activity of red leaf lettuce (Lollo Rosso) due to cultivation under plastic films varying in ultraviolet transparency. , 2007, Journal of agricultural and food chemistry.

[29]  G. Williamson,et al.  Effect of variety, processing, and storage on the flavonoid glycoside content and composition of lettuce and endive. , 2000, Journal of agricultural and food chemistry.

[30]  J. Harnly,et al.  A screening method for the identification of glycosylated flavonoids and other phenolic compounds using a standard analytical approach for all plant materials. , 2007, Journal of agricultural and food chemistry.