Isabel Estrella

Phenolic compounds in apples : varietal differences

ZusammenfassungNach HPLC-Trennung werden die phenolischen Verbindungen von Apfelfruchtfleisch,-Schale oder-Saft von fünf verschiedenen Apfelsorten analysiert. Die Hauptkomponenten (Catechine, Procyanidine, Hydroxyzimtsäureester mit Glucose oder Chinasäure und Flavonoidglykoside) werden quantitativ erfaßt. Die Verteilung der einzelnen Verbindungen hängt von der untersuchten Probe und der Apfelsorte ab.SummaryThe phenolic compounds in the flesh, skin and juice of five varieties of apples have been analysed by high performance liquid chromatography. The following major compounds were quantified: catechins, procyanidins, hydroxycinnamic acid esters and flavonoid glycosides. The phenolic content showed different patterns depending on the part of the fruit studied and the variety of the apple.

Determination of some structural features of procyanidins and related compounds by photodiode-array detection

Abstract In this work we have examined the use of a photodiode-array detector to identify unknown peaks correspoding to procyanidins and related compounds. The type of flavan-3-ol unit can be recognised from the absorption maximum (278.9) nm for catechin and epicatechin, and 270.6 nm for epigallocatechin), whereas the number of flavan-3-ol units does not affect this parameter. The min-max distance (distance between the minimum and the maximum in the original spectrum) decreases by 1.3 nm for each catechin or epicatechin unit. Gallates of flavan-3-ol can be detected by reference to the value of the convexity interval (distance between the inflection points before and after the maximum in the original spectrum).

Phenolic compounds in chestnut (Castanea sativa Mill.) heartwood. Effect of toasting at cooperage.

The phenolic and tannic composition of heartwood extracts from Castanea sativa Mill., before and after toasting in cooperage, were studied using HPLC-DAD and HPLC-DAD/ESI-MS, and some low molecular weight phenolic compounds and hydrolyzable tannins were found. The low molecular weight phenolic compounds were lignin constituents as the acids gallic, protocatechuic, vanillic, syringic, ferulic, and ellagic, the aldehydes protocatechuic, vanillic, syringic, coniferylic, and sinapic, and the coumarin scopoletin. Their patterns were somewhat different those of oak because oak does not contain compounds such protocatechuic acid and aldehyde and is composed of much lower amounts of gallic acid than chestnut. Vescalagin and castalagin were the main ellagitannins, and acutissimin was tentatively identified for the first time in this wood. Moreover, some gallotannins were tentatively identified, including different isomers of di, tri, tetra, and pentagalloyl glucopyranose, and di and trigalloyl-hexahydroxydiphenoyl glucopyranose, comprising 20 different compounds, as well as some ellagic derivatives such as ellagic acid deoxyhexose, ellagic acid dimer dehydrated, and valoneic acid dilactone. These ellagic derivatives as well as some galloyl and hexahydroxydiphenoyl derivatives were tentatively identified for the first time in this wood. The profile of tannins was therefore different from that of oak wood because oak only contains tannins of the ellagitannins type. Seasoned and toasted chestnut wood showed a very different balance between lignin derivatives and tannins because toasting resulted in the degradation of tannins and the formation of low molecular weight phenolic compounds from lignin degradation. Moreover, the different toasting levels provoked different balances between tannins and lignin constituents because the intensity of lignin and tannin degradation was in relation to the intensity of toasting.

HPLC study of the efficiency of extraction of phenolic compounds

SummaryThe rate of extraction of phenolic compounds in two different solvents has been studied by liquid chromatography (HPLC) under reverse phase, gradient elution conditions. The solvents were diethyl ether and ethyl acetate. The method has been applied to two natural samples, a white wine and apple pulp.

Phenolic compounds in a Spanish red wine aged in barrels made of Spanish, French and American oak wood

Abstract. A red Rioja wine was aged in barrels made of Spanish oak wood for 21 months. The evolutions of colour percentage intensity, families of phenolic compounds and low molecular weight phenolic compounds were studied in these wines and compared with those of the same wine aged in barrels made of French and American oak. The analysis of chromatic parameters and total anthocyanins indicates that the wines aged in Spanish and French oak wood barrels have similar chromatic characteristics, but are significantly different to those of wines aged in barrels made of American oak wood, indicating a different degree of modification of the colour. The ageing process also had an important influence on the low molecular weight polyphenols composition of wine. The evolution of these components allowed the production of wines with different characteristics, in relation to the type of wood used in barrel making process. On the other hand, Spanish oak wood can be considered suitable for barrel production for quality wines, since a wine aged in barrels made of Spanish oak wood showed similar and intermediate characteristics to those of the same wine aged in French and American oak woods.

Photodiode array detection for elucidation of the structure of phenolic compounds

A photodiode array detector was employed to obtain spectral data and to study a set of derived parameters in order to assign some structural features (functional group conjugated with aromatic ring, degree of substitution, position of substituents, etc.) to unknown chromatographic peaks of low-molecular-mass phenolics.

Effect of cooking and germination on phenolic composition and biological properties of dark beans (Phaseolus vulgaris L.)

Legumes are the basés diet in several countries. They hold a high nutritional value, but other properties related to human health are nowadays being studied. The aim of this work was to study the influence of processes (boiling or germination) on the phenolic composition of dark beans (Phaseolus vulgaris L. c.v. Tolosana) and their effect on their antioxidant, neuroprotective and anticancer ability. Phenolic composition of raw and processed dark beans was analysed by HPLC-PAD and HPLC-ESI/MS. The antioxidant activity was evaluated by ORAC. Astrocytes cultures (U-373) have been used to test their neuroprotective effect. Anticancer activities were evaluated on three different cell lines (renal adenocarcinoma (TK-10), breast adenocarcinoma (MCF-7) and melanoma (UACC-62)) by sulphorhodamine B method. Qualitative and quantitative differences in phenolic composition have been observed between raw and processed dark beans that influence the antioxidant activity, mainly for germinated samples which show a decrease of antioxidant capacity. Although every assayed extracts decreased reactive oxygen species release and exhibited cytotoxicity activities on cancer cell lines, raw beans proved to be the most active in neuroprotective and antitumoral effects; this sample is especially rich in phenolic compounds, mainly anthocyanins. This study further demonstrated that phenolic composition of dark beans is related with cooking process and so with their neuroprotective and anticancer activity; cooking of dark beans improves their digestion and absorption at intestinal level, while maintaining its protective ability on oxidative process at cellular level.

Phenolic Inhibitors of α-Amylase and Trypsin Enzymes by Extracts From Pears, Lentils, and Cocoa

Inhibition of α-amylase and trypsin by phenolic extracts of various fruit and vegetable foodstuffs (pears [ Pyrus communis ], lentils [ Lens esculenta ], and cocoa beans [ Theobroma cacao ]) was studied. An appropriate methodology for determining the percentage of inhibition of each enzyme was developed. A concomitant study carried out using standard substances (gallic acid, (+)-catechin, tannic acid, and condensed tannins) showed that polymeric phenols were more potent inhibitors than the simple forms, all of them having different behaviors towards the enzymes, depending on their chemical characteristics. The inhibitory potency of the extracts varied according to the phenolic composition of each and was intermediate between that of the simple and that of the more complex phenolic compounds. Inhibition of α-amylase by the phenolic extracts (at equal concentrations) was of the same order of magnitude, even though the phenolic nature and content in the three foodstuffs differed substantially. In contrast, in the case of trypsin, the lentil and cocoa extracts displayed inhibition 10 times greater than that of the pear extract.

Phenolic compound profiles and antioxidant capacity of persea americana mill. peels and seeds of two varieties

Avocado processing by the food and cosmetic industries yields a considerable amount of phenolic-rich byproduct such as peels and seeds. Utilization of these byproducts would be favorable from an economic point of view. Methanolic (80%) extracts obtained from lyophilized ground peels and seeds of avocado (Persea americana Mill.) of the Hass and Shepard varieties were characterized for their phenolic compound profiles using the HPLC-PAD technique. The structures of the identified compounds were subsequently unambiguously confirmed by ESI-MS. Compositional analysis revealed that the extracts contained four polyphenolic classes: flavanol monomers, proanthocyanidins, hydroxycinnamic acids, and flavonol glycosides. The presence of 3-O-caffeoylquinic acid, 3-O-p-coumaroylquinic acid, and procyanidin A trimers was identified in seeds of both varieties. Intervarietal differences were apparent in the phenolic compound profiles of peels. Peels of the Shepard variety were devoid of (+)-catechin and procyanidin dimers, which were present in the peels of the Hass variety. Peels of both varieties contained 5-O-caffeoylquinic acid and quercetin derivatives. The differences in the phenolic profiles between varietals were also apparent in the different antioxidant activity of the extracts. The peel extracts had a higher total phenolic compound content and antioxidant activity when compared to the seed extracts. The highest TEAC and ORAC values were apparent in peels of the Haas variety in which they amounted to 0.16 and 0.47 mmol Trolox/g DW, respectively. No significant (p > 0.05) differences were apparent between the TEAC values of seeds of the two varieties but the ORAC values differed significantly (p < 0.05). Overall these findings indicate that both the seeds and peel of avocado can be utilized as a functional food ingredient or as an antioxidant additive.

Phenolic Compounds in Cherry (Prunus avium) Heartwood with a View to Their Use in Cooperage

The phenolic and tannic composition of heartwood extracts from Prunus avium , commonly known as cherry tree, before and after toasting in cooperage were studied using HPLC-DAD and HPLC-DAD/ESI-MS. Nonflavonoid (16 compounds) and flavonoid (27 compounds) polyphenols were identified, 12 of them in only a tentative way. The nonflavonoids found were lignin constituents, and their pattern is different compared to oak, since they include compounds such as protocatechuic acid and aldehyde, p-coumaric acid, methyl vanillate, methyl syringate, and benzoic acid, but not ellagic acid, and only a small quantity of gallic acid. In seasoned wood we found a great variety of flavonoid compounds which have not been found in oak wood for cooperage, mainly, in addition to the flavan-3-ols (+)-catechin, a B-type procyanidin dimer, and a B-type procyanidin trimer, the flavanones naringenin, isosakuranetin, and eriodictyol and the flavanonols aromadendrin and taxifolin. Seasoned and toasted cherry wood showed different ratios of flavonoid to nonflavonoid compounds, since toasting results in the degradation of flavonoids, and the formation of nonflavonoids from lignin degradation. On the other hand, the absence of hydrolyzable tannins in cherry wood, which are very important in oak wood, is another particular characteristic of this wood that should be taken into account when considering its use in cooperage.