Josep Valls

Advanced separation methods of food anthocyanins, isoflavones and flavanols.

In recent years, increasing knowledge of the positive health effects of food polyphenols has prompted the need to develop new separation techniques for their extraction, fractionation and analysis. This article provides an updated and exhaustive review of the application of counter-current chromatography, high performance liquid chromatography, capillary electrophoresis, and their hyphenation with mass spectrometry to the study of food polyphenols. Flavonoids constitute the largest class of polyphenols, widely spread in the plant kingdom and common in human diet which has been the most widely studied with respect to their antioxidant and biological activities. The main subgroups are anthocyanins, catechins, isoflavones, flavonols and flavones. They are reported to exhibit antioxidant, anti-carcinogenic, anti-inflammatory, anti-atherogenic, anti-thrombotic, and immune modulating functions, among others. Since red fruit anthocyanins, soy isoflavones and flavanols from grapes and teas are currently the most used phenolic compounds for producing new nutraceuticals and functional foods, this review is focused on these three flavonoid groups.

Bioavailability of procyanidin dimers and trimers and matrix food effects in in vitro and in vivo models

Among procyanidins (PC), monomers, such as catechin and epicatechin, have been widely studied, whereas dimer and trimer oligomers have received much less attention, despite their abundance in our diet. Recent studies have showed that as dimers and trimers could be important in determining the biological effects of procyanidin-rich food, understanding their bioavailability and metabolism is fundamental. The purpose of the present work is to study the stability of PC under digestion conditions, the metabolism and the bioavailability by using a combination of in vitro and in vivo models. Simultaneously, the matrix effect of a carbohydrate-rich food on the digestibility and bioavailability of PC is investigated. The results show a high level of stability of PC under gastric and duodenal digestion conditions. However, the pharmacokinetic study revealed limited absorption. Free forms of dimers and trimers have been detected in rat plasma, reaching the maximum concentration 1 h after oral intake of a grape seed extract.

Rapid analysis of procyanidins and anthocyanins in plasma by microelution SPE and ultra‐HPLC

In the analysis of biological samples, such as plasma or serum, the quantity of sample available is a critical parameter in most cases. A good approach is the use of the microelution SPE (μSPE) plates as sample pre-treatment technique in which the loaded sample volume is low. An off-line μSPE and ultra-performance LC-ESI-MS/MS (UPLC-ESI-MS/MS) method was developed and validated to determine procyanidins and anthocyanins in spiked plasma samples. The sample pre-treatment μSPE allowed the simultaneous determination of procyanidins and anthocyanins from plasma by using a small sample volume (350 μL) and without an evaporation step previous to the chromatographic analysis. Moreover, the use of UPLC technique allowed to determine the studied compounds at low concentration levels in a short analysis time (12.5 min approximately). Then, the developed method was applied to determine the studied compounds, procyanidins and anthocyanins, and their metabolites in rat plasma samples. Previously, the rats had consumed 5000 mg/kg of a grape pomace extract and the plasma was extracted 4 h after administration. The procyanidins catechin and epicatechin glucuronide, methyl catechin and epicatechin glucuronide, and methyl catechin and epicatechin sulphate were detected at μM concentration level, and the parent anthocyanins at nM.

Phenolic compounds and somatic embryogenesis in cotton (Gossypium hirsutum L.)

Studies of phenolic compounds were performed during cell suspension cultures in relation with the induction of embryogenic structures in two cultivars of cotton. Coker 312 produced embryogenic structures, unlike R405-2000 which was found to be a non-embryogenic cultivar. Embryogenesis induction in Coker 312 was strongly linked to a higher content of caffeic, ferulic and salicylic acids and to the appearance of p-coumaric acid, benzoic acid, trans-resveratrol, catechin and naringenin.

Relaxation induced by red wine polyphenolic compounds in rat pulmonary arteries: lack of inhibition by NO‐synthase inhibitor

Some red wine polyphenols exert nitric oxide (NO)‐dependent relaxation in systemic arteries, following activation of endothelial NO synthase (eNOS). In this study, the effect of red wine polyphenols was determined in rat intrapulmonary arteries, and the effect of some of these compounds was compared with the responses obtained in rat aorta. In pulmonary arteries, red wine polyphenolic extract (> 300 μg/mL) exerted relaxation that was not inhibited by the NOS inhibitor Nω‐nitro‐l‐arginine methylester (l‐NAME) or endothelium removal. Among the several fractions obtained from the extract, the one enriched with anthocyanins was less active than fractions containing non‐anthocyanins. Among the latter, the most active for relaxing pulmonary arteries was the one enriched in the stilbene derivative trans‐resveratrol (relaxation for concentration >10 μg/mL). Trans‐piceid, the glucoside derivative of trans‐resveratrol, was almost inactive. Trans‐resveratrol‐induced relaxation, as well as relaxation to the anthocyanin delphinidin, was l‐NAME‐insensitive in pulmonary arteries. In aorta, trans‐resveratrol and trans‐piceid exerted similar effects to those in pulmonary arteries that were also not inhibited by l‐NAME. However, red wine polyphenolic extract and delphinidin induced relaxation of aorta at much lower concentrations (about 10 μg/mL) than in pulmonary arteries, and their effects were inhibited by l‐NAME. These data show differences between small intrapulmonary arteries and systemic conductance arteries in their responses to red wine polyphenols, the major difference being that the relaxant effect of these compounds is not blunted by NOS inhibitor in pulmonary arteries. They suggest that red wine polyphenols act directly on smooth muscle to promote pulmonary artery relaxation.

First evidence of trans-resveratrol production in cell suspension cultures of cotton (Gossypium hirsutum L.)

For the first time, trans-resveratrol, a stilbene, has been identified in cotton cell suspensions. Cell suspensions of Coker 312, a cultivar which produces embryogenic structures, acccumulate trans-resveratrol contrary to those of cultivar R405-2000, which do not. This stilbene may be a good phenolic marker for induction of somatic embryogenesis in cotton.

Polyphenol levels in two cotton (Gossypium hirsutum L.) callus cultures

Abstract We study the production of polyphenols by callus cultures from two cultivars of cotton (Gossypium hirsutum L.). Coker 312 produces the best calli and has embryogenic potential contrary to that of R405-2000, which is non- embryogenic. There is a relationship between the level of phenolic compounds and the callus cultures. Callogenesis in Coker 312 is highly correlated to a higher content of catechin, caffeic acid, ferulic acid, rutin, o—coumaric acid and salicylic acid. On the other hand, the cinnamic acid derivates (trans-cinnamic, cis and trans—methoxycinnamic acids) found in high amounts in R405-2000 calli could have a negative influence on the induction of cotton callogenesis.

Plant-derived phenolics inhibit the accrual of structurally characterised protein and lipid oxidative modifications.

Epidemiological data suggest that plant-derived phenolics beneficial effects include an inhibition of LDL oxidation. After applying a screening method based on 2,4-dinitrophenyl hydrazine- protein carbonyl reaction to 21 different plant-derived phenolic acids, we selected the most antioxidant ones. Their effect was assessed in 5 different oxidation systems, as well as in other model proteins. Mass-spectrometry was then used, evidencing a heterogeneous effect on the accumulation of the structurally characterized protein carbonyl glutamic and aminoadipic semialdehydes as well as for malondialdehyde-lysine in LDL apoprotein. After TOF based lipidomics, we identified the most abundant differential lipids in Cu++-incubated LDL as 1-palmitoyllysophosphatidylcholine and 1-stearoyl-sn-glycero-3-phosphocholine. Most of selected phenolic compounds prevented the accumulation of those phospholipids and the cellular impairment induced by oxidized LDL. Finally, to validate these effects in vivo, we evaluated the effect of the intake of a phenolic-enriched extract in plasma protein and lipid modifications in a well-established model of atherosclerosis (diet-induced hypercholesterolemia in hamsters). This showed that a dietary supplement with a phenolic-enriched extract diminished plasma protein oxidative and lipid damage. Globally, these data show structural basis of antioxidant properties of plant-derived phenolic acids in protein oxidation that may be relevant for the health-promoting effects of its dietary intake.

A review of dietary stilbenes: sources and bioavailability

Stilbenes are a class of phenolic metabolites found in various edible plants, such as grapevine, berries and peanuts. Their bioactivitiy and their potential benefits for human health have been the subject of several studies. Among all identified stilbenes, resveratrol has been particularly studied and results from literature showed that it presents several biological activities, including antioxidant, anti-inflammatory and antiproliferative effects. Likewise, some researches focused on other stilbenes and highlighted similar biological activity for those compounds. However, stilbenes present a high diversity in their phenolic structures (various chemical substituents and polymerization) which is a determining factor of their absorption and metabolism rates. Consequently, this could affect the effectiveness of stilbenes in vivo. In this context, an evaluation of the bioavailability and metabolism of stilbenes is necessary to move forward with pharmacological and clinical studies. Hence, this review aims to present recently obtained data and results concerning stilbenes sources and bioavailability, as a contribution to the valorization of the role of dietary stilbenes in the human diet.