Comparative Study of Phenolic Profile, Antioxidant Capacity, and Color-composition Relation of Roselle Cultivars with Contrasting Pigmentation.

Roselle is a plant that accumulates anthocyanins significantly, hence its importance as food coloring and as a source of antioxidant compounds for human health. This study was aimed to determine phenolic composition and antioxidant capacity of methanolic extracts, and beverages obtained from native roselle cultivars in Mexico (Negra, Sudan, Rosa and Blanca) with different degrees of pigmentation, and to establish the color-composition relationship. Chromatographic methods were used to determine phenolic compounds: flavanols, flavonols, benzoic, hibiscus and phenolic acids as well as two main anthocyanins (cyanidin 3-sambubioside and delphinidin 3-sambubioside). The antioxidant capacity was evaluated by ABTS and FRAP assays. Tristimulus colorimetry showed to be a useful technique to determine the color-composition relationship, leading to equations that allowed to predict anthocyanin content of roselle (R > 0.84). Also, a stepwise linear discriminant analysis (SLDA) was developed in order to classify roselle cultivars. The obtained mathematical model could be an important tool to be used in colorimetric characterization of functional compounds used in food processing.

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.