Dolores Hernanz

Assessment of white grape pomace from winemaking as source of bioactive compounds, and its antiproliferative activity

The antiproliferative effects of a purified white grape pomace extract (PWGPE), as well as of some phenolic standards on colon cancer cells were examined. The phenolic composition of the PWGPE was determined by rapid resolution liquid chromatography/mass spectrometry (RRLC/MS). The PWGPE had 92.6, 43.3 and 6.01mg/g of flavanols, flavonols and phenolic acids, respectively and, along with pure catechin, epicatechin, quercetin and gallic acid, they were all found capable of inhibiting cellular proliferation. PWGPE (100μg/ml) inhibited the proliferation of cells by 52.1% at 48h, whilst catechin, epicatechin, quercetin and gallic acid (60μg/ml) inhibited growth by 65.2%, 62.2%, 81.0% and 71.0%, respectively, at 72h. The PWGPE is an interesting source of phenolic compounds with antiproliferative properties, that could be of interest in the food and pharmaceutical industries.

Study of Zalema Grape Pomace: Phenolic Composition and Biological Effects in Caenorhabditis elegans

The phenolic composition of the extractable fraction of Zalema grape pomace has been analyzed by HPLC-DAD-MS and consisted of mainly flavanols and flavonols (122.75 and 23.11 mg/100 g dry pomace, respectively). The antioxidant activity has been determined by in vitro FRAP, ABTS, and ORAC assays (11.7, 34.9, and 63.6 mmol of Trolox equivalents (TE) per 100 g of dry pomace, respectively) and in vivo using the model organism Caenorhabditis elegans . Cultivation of C. elegans in media containing 100 μg/mL dry pomace extract increased the survival of worms submitted to thermally induced oxidative stress, whereas a decrease in the rate of worm survival was found for 300 μg/mL extract. Interestingly, the levels of reactive oxygen species (ROS) were significantly decreased in stressed worms treated with the pomace extract at the two concentration levels. Further studies are required to explain this unexpected behavior, as well as to determine the compounds and mechanisms involved in the observed effects.

Comparative study of the enological potential of different winemaking byproducts: implications in the antioxidant activity and color expression of red wine anthocyanins in a model solution.

Different white winemaking byproducts (pomace, skins, seeds, and stems) were compared as natural sources of phenolic compounds having biological and sensory properties of enological interest. Antioxidant and copigmentation effects of these byproducts were studied in a wine-like model solution. RRLC-DAD was used to establish differences in the phenolic composition, and the ABTS method was used to compare the antioxidant activities. Spectrophotometric and colorimetric analyses were performed to assess the magnitude of copigmentation and the changes induced in the color expression of red wine anthocyanins. Antioxidant and copigmentation properties significantly varied depending on the type of byproduct, which was related to their qualitative and quantitative phenolic composition. Seeds and pomace showed the highest antioxidant potential, whereas skins and pomace led to the strongest and visually perceptible color effects on red wine anthocyanins by multiple copigmentation (darker, more saturated, and vivid bluish colors). Results open the possibility of technological applications for the wine industry based on reusing winemaking byproducts to improve the biological value and color characteristics of red wines.

Development and validation of a rapid resolution liquid chromatography method for the screening of dietary plant isoprenoids: carotenoids, tocopherols and chlorophylls.

A rapid resolution liquid chromatography (RRLC) method was developed and validated for the simultaneous determination of nine carotenoids compounds (violaxanthin, lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, lycopene, phytoene, phytofluene), four tocopherols and four chlorophylls and derivates (chlorophylls and pheophytins). The methodology consisted in a micro-extraction procedure with or without saponification and subsequent analysis by RRLC. The limits of detection were <0.07 μg for carotenoids and tocopherols and <0.08 μg for chlorophylls and derivatives. The overall precision values (intra- and inter-day) were lower than 12% when samples were not saponified and <27.6%, when the saponification step was performed. The recovery of the method without the saponification step ranged from 92% to 107%, whilst that when saponification was carried out ranged from 60% for α-tocopherol to 82% for β-carotene. Finally, the applicability of the method was demonstrated by the identification and quantification of isoprenoids in different samples. The methodology is appropriate for the high-throughput screening of dietary isoprenoids in fruits and vegetables.

Detailed phenolic composition of white grape by-products by RRLC/MS and measurement of the antioxidant activity

The development and validation of a rapid method of RRLC has been carried out to determine the phenolic composition of winemaking by-products (pomaces, seeds, skins and stems). Thirty-one phenolic compounds belonging to three groups (flavanols, flavonols and phenolic acids) have been identified by use of standards and mass spectrometric detection, and quantified by using the corresponding external standard calibration plot, in a 16-min run. The validation was realized calculating the repeatability, the reproducibility and the limits of detection (LOD) and quantification (LOQ), from standards solutions. The limits of detection and quantification were in the range of 0.16-1.09 and 0.52-3.63 mg/L, respectively, and good repeatability (R.S.D. values <1.5%) and reproducibility (R.S.D. values <5.5%) were found. Results confirmed that the method is effective and suitable for determination of phenolic compounds in winemaking by-products. Seeds, skins, stems and pomaces exhibited a different qualitative and quantitative phenolic profile and different antioxidant activities.

Multivariate statistical analysis of the color-anthocyanin relationships in different soilless-grown strawberry genotypes.

Apart from the need to assess the color of foods due to its preponderant role in their acceptability, there is currently a new trend consisting in the study of the relationships between the color and the pigments accounting for it. The color of five strawberry varieties cultivated in two different soilless systems has been studied, and an array of multivariate statistical methods have been performed to single out the color parameters that best discriminate among the different samples surveyed and to correlate them with the pigment content. It is concluded that there is not a direct relationship between the external and flesh colorations of the berries. Additionally, after discriminant methods were applied, it was noticed that, taking into account the strawberry varieties, >90% of the cases could be correctly classified, a noticeably lower percentage of correct classification (around 60%) being obtained when the type of cultivation system was selected as the criterion for discrimination. The best correlations of pigment-color coordinates were found between pelargonidin-3-rutinoside and the external a* (r= -0.87) followed by pelargonidin-3-glucoside and the internal L* (r= -0.72).

The Use of Grape Seed Byproducts Rich in Flavonoids to Improve the Antioxidant Potential of Red Wines.

The influence of adding seeds from grape pomace during Syrah wine fermentation in a warm climate has been studied. Seeds of Pedro Ximenez variety were rich in phenolic compounds, mainly flavonoids such as catechin and procyanidins. Changes in total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity of red wines were observed. These changes depended on the vinification stage and the amount of seeds (SW: 450 g or DW: 900 g seeds/150 kg grapes) applied. In general, antioxidant activity was greater when a simple dose (SW) was considered. Results indicate that seeds rich in flavonoids could be used as wine additives, which could improve the antioxidant potential of red wines in a warm climate.

Foam mat drying of Tommy Atkins mango: Effects of air temperature and concentrations of soy lecithin and carboxymethylcellulose on phenolic composition, mangiferin, and antioxidant capacity

In this study, foam mat drying was applied to Tommy Atkins mango. Using a multifactorial design, the effect of soy lecithin (L) and carboxymethylcellulose (CMC) used as foam stabilizers (0-1.50g/100g), as well as temperature (T) (53-87°C), on phenolic content and antioxidant capacity of mango were evaluated. Mango pulp contains antioxidant, such as mangiferin, that can be utilized in foods to enhance their functional properties. Our results indicated that L and T had negative effects (p<0.05) on the phenolic content and antioxidant capacity, whereas CMC had a positive effect (p<0.05). Increasing the total amount of phenolic compounds present in dried mango contributed to the higher antioxidant capacity after the drying process. This study concluded that a drying T of 80°C, and a concentration of 0.30g/100g of CMC and L are optimal for increased retention of phenolic compounds and antioxidant capacity.

Effects of in vitro gastrointestinal digestion on phenolic compounds and antioxidant activity of different white winemaking byproducts extracts

The effect of in vitro gastrointestinal digestion on phenolic composition and antioxidant activity of different white winemaking byproducts extracts (grape pomace and its parts: seeds, skins and stems) was evaluated. Fourteen individual phenolic compounds were evaluated by UHPLC. The antioxidant activity was measured by DPPH and ORAC assays. Differences on phenolic profile and antioxidant activity were observed depending on the digestion phase, the type of byproduct, the phenolic group and the antioxidant activity assay. In general, digestion had a reducing effect on TPC and antioxidant activity; however, ORAC values of seed and stem extracts increased after digestion and some recovery indexes of the phenolic groups were very high. Results indicate that extracts from white winemaking byproducts are a reliable source of bioaccessible antioxidant compounds, which could be used as functional food ingredients.

Cyclic voltammetry to evaluate the antioxidant potential in winemaking by-products

Grape pomace is composed of seeds, skins and stems that are an important source of phenolic substances, which have antioxidant properties and potential benefits to human health. Cyclic voltammetry (CV) has been used to measure the total antioxidant potential of different winemaking by-products. The electrochemical behavior of pomace, seeds, skins and stems was measured by CV and lipid peroxidation inhibition by thiobarbituric acid reactive substances (TBARS) method. Differences for the electrochemical parameter were found between the by-products, pomace and seeds, which presented the greatest voltammetric peak area. Furthermore, the by-products induced inhibition of lipid peroxidation in rat liver homogenates. Pomace and seeds showed higher capacity to inhibit lipid peroxidation than stems and skins, which could be because these by-products are richer in flavanols. Simple regression analyses showed that voltammetric parameters are highly correlated to the values obtained for lipid peroxidation inhibition. CV is a promising technique to estimate the total antioxidant potential of phenolic extract from winemaking by-products.