pubs.acs.org/JAFC Published on Web 10/19/2009 © 2009 American Chemical Society 10134 J. Agric. Food Chem. 2009, 57, 10134–10142 DOI:10.1021/jf901450z Profile of Plasma and Urine Metabolites after the Intake of Almond [Prunus dulcis (Mill.) D.A. Webb] Polyphenols in Humans MIREIA URPI-SARDA, † IGNACIO GARRIDO, ‡ MARI ´ A MONAGAS, ‡ CARMEN GO ´ MEZ-CORDOVE ´ S, ‡ ALEXANDER MEDINA-REMO ´ N, † CRISTINA ANDRES-LACUEVA,* ,† AND BEGON ˜ A BARTOLOME ´ ‡ † Nutrition and Food Science Department, XaRTA, INSA, CONSOLIDER INGENIO 2010 Program (FUN-C-FOOD CSD2007-063), Pharmacy Faculty, University of Barcelona, Avinguda Joan XXIII s/n, 08028 Barcelona, Spain, and ‡ Instituto de Fermentaciones Industriales (CSIC), 28006 Madrid, Spain Nut skins are considered to be a rich source of polyphenols and may be partially responsible for the numerous health effects associated with nut consumption. However, more bioavailability studies of nut skin polyphenols are needed to understand the health effects derived from nut consumption. The aim of the present study was to determine the profiles of both phase II and microbial-derived phenolic metabolites in plasma and urine samples before and after the intake of almond skin polyphenols by healthy human subjects (n =2). Glucuronide, O-methyl glucuronide, sulfate, and O-methyl sulfate derivatives of (epi)catechin, as well as the glucuronide conjugates of naringenin and glucuronide and sulfate conjugates of isorhamnetin, were detected in plasma and urine samples after consumption of almond skin polyphenols. The main microbial-derived metabolites of flavanols, such as 5-(dihydroxyphenyl)-γ-valerolactone and 5-(hydroxymethoxyphenyl)-γ-valerolactone, were also detected in their glucuronide and sulfate forms. In addition, numerous metabolites derived from further microbial degradation of hydroxyphenylvalerolactones, including hydroxyphenylpropionic, hydroxyphenylacetic, hydroxycinnamic, hydroxybenzoic, and hydroxyhippuric acids, registered major changes in urine after the consumption of almond skin polyphenols. The urinary excretion of these microbial metabolites was estimated to account for a larger proportion of the total polyphenol ingested than phase II metabolites of (epi)catechin, indicating the important role of intestinal bacteria in the metabolism of highly polymerized almond skin polyphenols. To the authors’ knowledge this study constitutes the most complete report of the absorption of almond skin polyphenols in humans. KEYWORDS: Almond; polyphenols; metabolites; microflora; hydroxyphenylvalerolactone INTRODUCTION Polyphenols are among the most abundant bioactive com- pounds of the Mediterranean diet and may play a key role in the prevention of cardiovascular and neurodegenerative diseases and cancer. Among the foods traditionally associated with the Medi- terranean diet, the consumption of almonds [Prunus dulcis (Mill.) D.A. Webb] has been associated with beneficial protection against cardiovascular and obesity-related diseases ( 1 ). More- over, Jenkins et al. ( 2 , 3 ) have also demonstrated that consump- tion of whole almonds decreases postprandial glycemia, insulinemia, and oxidative protein damage in humans. In fact, results from in vitro studies have revealed that almond skin polyphenols act in synergy with vitamins C and E to protect low-density lipoprotein (LDL) from oxidation ( 4 , 5 ) and enhance the antioxidant defense in other physiological environments ( 6 ). Besides their role in the prevention of cardiovascular and obesity- related diseases, results from in vitro studies have revealed that ground almonds significantly increased the populations of bifido- bacteria and Eubacterium rectale, resulting in a higher prebiotic index (4.43) than for commercial prebiotic fructooligosaccharides (4.08) ( 7 ), indicating a potential prebiotic effect of almond seeds. Almond skins are considered to be a very rich source of polyphenols. Non-flavonoid compounds include protocatechuic aldehyde and protocatechuic, vanillic, p-hydroxybenzoic, trans-p- coumaric, and chlorogenic acids ( 8 -10 ). Flavonoid compounds identified in almond skins include flavanols, flavonols, dihydro- flavonols, and flavanones. The monomers (þ)-catechin and (-)- epicatechin, as well as procyanidins B1, B2, B3, and B4, have been identified in almond skins ( 11 , 12 ). Although it was originally thought that almond skin proanthocyanidins were exclusively constituted of (þ)-catechin and (-)-epicatechin units linked by B-type bonds ( 11 , 13 ), later studies revealed the presence of delphinidin after n-butanol-HCl hydrolysis of almond seed *Corresponding author (telephone þ34-93-4034840; fax þ34-93- 4035931; e-mail candres@ub.edu).