Priscilla Siqueira Melo

Antioxidant Activity of Brazilian Vegetables and Its Relation with Phenolic Composition

Vegetables are widely consumed in Brazil and exported to several countries. This study was performed to evaluate the phenolic content and antioxidant activity of vegetables commonly consumed in Brazil using five different methods, namely DPPH and ABTS free radical, β-carotene bleaching, reduction of Fe3+ (FRAP), oxidative stability in Rancimat, and the chemical composition using gas chromatography-mass spectrometry (GC-MS). The content of phenolic compounds ranged from 1.2 mg GA/g (carrot) to 16.9 mg GA/g (lettuce). Vegetables presenting the highest antioxidant activity were lettuce (77.2 μmol Trolox/g DPPH•; 447.1 μmol F2+/g FRAP), turmeric (118.6 μmol Trolox/g ABTS•+; 92.8% β-carotene), watercress and broccoli (protective factor 1.29—Rancimat method). Artichoke, spinach, broccoli, and asparagus also showed considerable antioxidant activity. The most frequent phenolic compounds identified by GC-MS were ferulic, caffeic, p-coumaric, 2-dihydroxybenzoic, 2,5-dihydroxybenzoic acids, and quercetin. We observed antioxidant activity in several vegetables and our results point out their importance in the diet.

Winery by-products: extraction optimization, phenolic composition and cytotoxic evaluation to act as a new source of scavenging of reactive oxygen species.

Nearly 20 million tons of winery by-products, with many biological activities, are discarded each year in the world. The extraction of bioactive compounds from Chenin Blanc, Petit Verdot, and Syrah grape by-products, produced in the semi-arid region in Brazil, was optimized by a Central Composite Rotatable Design. The phenolic compounds profile, antioxidant capacity against synthetic free radicals (DPPH and ABTS), reactive oxygen species (ROS; peroxyl radical, superoxide radical, hypochlorous acid), cytotoxicity assay (MTT) and quantification of TNF-α production in RAW 264.7 cells were conducted. Gallic acid, syringic acid, procyanidins B1 and B2, catechin, epicatechin, epicatechin gallate, quercetin 3-β-d-glucoside, delfinidin 3-glucoside, peonidin 3-O-glucoside, and malvidin 3-glucoside were the main phenolic compounds identified. In general, rachis showed higher antioxidant capacity than pomace extract, especially for Chenin Blanc. All extracts showed low cytotoxicity against RAW 264.7 cells and Petit Verdot pomace suppressed TNF-α liberation in vitro. Therefore, these winery by-products can be considered good sources of bioactive compounds, with great potential for application in the food and pharmaceutical industries.

Bioassay - guided isolation of proanthocyanidins with antioxidant activity from peanut (Arachis hypogaea) skin by combination of chromatography techniques.

Purification and bioassay-guided fractionation were employed to isolate proanthocyanidins with antioxidant activity from peanut skin (Arachis hypogaea Runner 886). The crude extract was prepared with acetone (60% v/v) and purified using chromatographic methods, including a semipreparative HPLC technique. As a result, two proanthocyanidins were isolated and identified using NMR, epicatechin-(2 β → O → 7, 4 β → 8)-catechin (proanthocyanidin A1) and epicatechin-(β → 2 O → 7, 4 β → 8)-epicatechin (proanthocyanidin A2). Despite the structural similarity, differences were observed in their antioxidant activity. Proanthocyanidin A1 proved to be more active, with EC50 value for DPPH radical scavenging of 18.25 μg/mL and reduction of Fe(3+)-TPTZ complex of 7.59 mmol/g, higher than that of synthetic antioxidant BHT. This compound evaluated by ABTS(+) was similar to that of natural quercetin. Therefore, peanut skin is an important source of bioactive compounds that may be used as a mild antioxidant for food preservation.

Composição fenólica e atividade antioxidante de resíduos agroindustriais

Nowadays, the agro-industrial processing produces millions of tons of wastes. Many of them are rich in bioactive compounds, being a potential natural source of these substances. This study aimed to evaluate the content of total phenolics, antioxidant activity and phenolic composition of residues generated by three Brazilian agribusiness: Isabel grape pomace (PI) (Vitis labrusca), Verdejo grape pomace (PV) (Vitis vinifera) and guava pomace (PG) (Psidium guajava). The results of total phenolics content (mg GAE g-1) found in the ethanol and aqueous extracts of residues were: PV (20.94±0.46; 8.03±0.43)>PI (16.57±0.19; 4.41±0.01)>PG (3.41±0.09; 1.88±0.06). High antioxidant activity of these extracts, particularly PV and PI, was found by the methods DPPH ●, ABTS ● and beta-carotene bleaching method. A strong positive correlation between antioxidant activity and content of total phenolic compounds was found. The following phenolic compounds were found by gas chromatography with mass spectrometry (GC-MS): gallic acid, epicatechin, quercetin (PV, PI and PG); isovanilic acid (PI, PG), p-coumaric acid (PI), caffeic acid and resveratrol (PV, PI). The results show that these residues, particularly the wineries, are rich in bioactive substances and should be exploited by the food industry and pharmaceuticals.

Antioxidative and prooxidative effects in food lipids and synergism with α-tocopherol of açaí seed extracts and grape rachis extracts

Extracts of açaí seed and of grape rachis alone or in combination with α-tocopherol were evaluated as antioxidants in (i) bulk soybean oil, (ii) soybean oil liposomes and (iii) soybean-oil/water emulsions. The extracts made with 57% aqueous ethanol showed an antioxidant activity not dependent on concentration for grape rachis extracts and a concentration-dependent prooxidative activity for açaí seed extracts in bulk soybean oil. Both the extracts, however, protected liposome suspensions and oil/water emulsions against lipid oxidation. Synergism was demonstrated when extracts were combined with α-tocopherol, effects explained by the solubility of extract components in the water-phase and of α-tocopherol in the lipid-phase. Phenolic profiling of the extracts by U-HPLC-ESI-LTQ-MS was used to identify active antioxidants. Açaí seed and grape rachis extracts served as good sources of procyanidins and flavan-3-ols, imparted high antioxidant activity especially when combined with α-tocopherol and are suggested for protection of food oil/water emulsions.

Exploration of avocado by-products as natural sources of bioactive compounds

This study aimed to evaluate the antioxidant, anti-inflammatory, and cytotoxic properties and phenolic composition of peel and seed of avocado varieties Hass and Fuerte using green solvents. Ethanol soluble compounds were identified in peel and seed of both varieties using HPLC-MS/MS and quantified using HPLC-DAD. Agro-industrial by-products of both varieties exhibited high radical scavenging activity against synthetic free radicals (DPPH and ABTS) and reactive oxygen species (peroxyl, superoxide, and hypochlorous acid) and high ability to reduce Fe3+ to Fe2+. The main compounds with significant contribution to the antioxidant activity determined by online HPLC-ABTS●+ analyses were procyanidin B2 and epicatechin in the peel and trans-5-O-caffeoyl-D-quinic acid, procyanidin B1, catechin, and epicatechin in the seed. Peel of Fuerte significantly suppressed TNF-α and nitric oxide (NO) release (459.3 pg/mL and 8.5 μM, respectively), possibly because of the high phenolic content and antioxidant activity detected. Avocado agro-industrial by-products can be used for food and pharmaceutical purposes due to their antioxidant and anti-inflammatory properties.

Can we conserve trans-resveratrol content and antioxidant activity during industrial production of chocolate?: Trans-resveratrol contents during production of chocolate

BACKGROUND Cocoa exhibits high content of phenolic compounds, among which trans-resveratrol stands out, associated with several bioactive activities such as antioxidant properties. Chocolate contains reduced amounts of these bioactive compounds due to losses during the production process. Therefore, this study aimed to assess changes in total phenolic content, and specifically trans-resveratrol, as well as changes in the antioxidant activity of cocoa and its products during industrial production of chocolate. RESULTS A total of ten different cocoa products were analyzed. The processes of fermentation and roasting caused significant loss of total phenolic compounds and antioxidant activity. The high temperature of roasting had a major influence on this loss (71% for total phenolic compounds and 53-77% for antioxidant activity), except for trans-resveratrol. The trans-resveratrol content formed after fermentation (9.8 μg kg-1 ) showed little variation during the processes, and it was detected in higher concentrations both in natural (11.4 μg kg-1 ) and in alkalized cocoa powder (13.5 μg kg-1 ). Alkalization of cocoa products led to loss of capacity of deactivating superoxide radical. CONCLUSION These findings contribute to the optimization of the production process of chocolate and other food products containing cocoa and its derivatives, aiming to better preserve their bioactive compounds.