Rosa Carvalho

Seasonal effects on bioactive compounds and antioxidant capacity of six economically important brassica vegetables.

Research on natural and bioactive compounds is increasingly focused on their effects on human health, but there are unexpectedly few studies evaluating the relationship between climate and natural antioxidants. The aim of this study was analyze the biological role of six different Brassica vegetables (Brassica oleracea L. and Brassica rapa L.) as a natural source of antioxidant compounds. The antioxidant activity may be assigned to high levels of L-ascorbic acid, total phenolics and total flavonoids of each sample. The climate seasons affected directly the concentration of bioactive components and the antioxidant activity. Broccoli inflorescences and Portuguese kale showed high antioxidant activity in Spring-Summer whilst turnip leaves did so in Summer-Winter. The Brassica vegetables can provide considerable amounts of bioactive compounds and thus may constitute an important natural source of dietary antioxidants.

Phytochemical characterization and antioxidant properties of baby-leaf watercress produced under organic production system

The aim of this study was to evaluate the phytochemical composition and the antioxidant properties of watercress (Nasturtium officinale R. Br., Brassicaceae) produced under organic production system. Fresh baby-leaf watercress samples were collected from local organic farms. High performance liquid chromatography with diode array detection (HPLC-DAD) and high performance liquid chromatography with diode array detection mass spectrometry (HPLC-MS) were used to assess the phytochemical composition, and spectrophotometric methods were used to assess the antioxidant capacity. Two major classes of healthier secondary plant metabolites were identified: phenolics and glucosinolates. The major phenolics determined were chlorogenic acid, quercetin-3-O-rutinoside, dicaffeoyltartaric acid, and isorhamnetin. The glucosinolates were composed exclusively of gluconasturtiin, the precursor of the anticarcinogenic, and antimicrobial compound 2-phenylethyl isothiocyanate. The extracts of organic young baby-leaf watercress presented high antioxidant capacity and this property was highly related with caffeic acid, quercetin-3-O-rutinoside, isorhamnetin, and glucosnastrutiin. The results achieved showed that baby-leaf watercress can provide high contents of antioxidant compounds at levels even superior to similar adult plant material.

Influence of Nitrogen and Sulfur Fertilization on the Mineral Composition of Broccoli Sprouts

ABSTRACT Broccoli sprouts (Brassica oleraceae var. italica) have been attributed health protective effects based on their glucosinolate content, and thus, are recommended in diets. However, no information is available on the mineral content of this novel product and how fertilization might influence it. The influence of nitrogen (N) and sulfur (S) applications (0, 14, and 28 mg· N dish−1 and 0, 4.5, and 9 mg· S dish−1) on the mineral content [N, S, potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), chloride (Cl), and silicon (Si)] of broccoli sprouts (Brassica oleraceae var. italica cv. ‘Marathon’) was determined 11 d after sowing. It was found that N and S fertilization significantly (P < 0.001) influenced the uptake of all elements except phosphorus (P). Sulfur concentrations in broccoli sprouts varied between 11.4 and 15.2 mg· g−1 (dw), while the Ca, Mg, P, K, and Na concentrations were below 10 mg· g−1 (dw). The Cl contents ranged from 13.6 to 23.1 mg· g−1 (dw). The highest S concentration was found when 9 mg· dish−1 S and 14 mg· dish−1 N was applied. A higher N rates of 28 mg· dish−1, N yielded no higher S uptake. The significantly (P < 0.05) highest Ca, Mg, and Na concentrations were found in the control treatments, while this effect proved to be not consistent for P. The results clearly revealed that N and S fertilization increased biomass production even in the early growth stages. With view to maintaining high Ca concentrations an application in the form of ammonium sulfate would be preferable.

Valorization of solid wastes from chestnut industry processing: Extraction and optimization of polyphenols, tannins and ellagitannins and its potential for adhesives, cosmetic and pharmaceutical industry.

The aim of the current study was to evaluate the potential of chestnut peels to produce pomaces enhanced with tannins to be used in the formulations of wood adhesives, leather tanning or as natural antioxidants in food, cosmetic and pharmaceutical industry. An analytical procedure was planned as 2 factorial design to analyze the influence of solvent (water, Na2SO3 and NaOH at different concentrations of 1, 2, 4, and 8% in water) and extraction time (30, 60, and 120, 240, 480 and 960min) on extraction yield, pH, Stiasny index, and tannins. HPLC-diode array detector equipped with an ionization mass spectrophotometer was used to assess the polyphenol composition. Our results showed that both extraction properties and phytochemicals were significantly affected (P<0.001) by all independent factors. The main tannins identified were the hydrolyzable gallic acid, vescalagin castalagin and ellagic acid, and the condensed epigallocatechin, catechin and epicatechin. The solvent 1% Na2SO3 was more effective to extract the condensed tannins whilst hydrolyzable tannins were extracted efficiently by 1% NaOH. The multivariable analysis and the Pearsons correlation coefficients showed a direct association between Stiasny number and the average levels of condensed tannins.

Effects of agriculture production systems on nitrate and nitrite accumulation on baby-leaf salads

Nitrate and nitrite are widespread contaminants of vegetables, fruits, and waters. The levels of these compounds are increased as a result of using organic wastes from chemical industries, domestic wastes, effluents, nitrogenous fertilizers, and herbicides in agriculture. Therefore, determining the nitrate and nitrite levels in biological, food, and environmental samples is important to protect human health and the environment. In this context, we set this study, in which we report the effect of production system (conventional and organic) on the accumulation of nitrates and nitrites in fresh baby-leaf samples. The average levels of the nitrate () and nitrite () contents in six different baby-leaf salads of a single species (green lettuce, red lettuce, watercress, rucola, chard, and corn salad) produced in organic and conventional agriculture system were evaluated. Spectrophotometric analytical method recently published was validated and used. Nitrates and nitrites were detected in all samples. The nitrates levels from organic production varied between 1.45 and 6.40 mg/kg fresh weight (FW), whereas those from conventional production ranged from 10.5 to 45.19 mg/kg FW. The nitrites content was lower than nitrates and ranged from 0.32 to 1.89 mg/kg FW in organic production system and between 0.14 and 1.41 mg/kg FW in conventional production system. Our results showed that the nitrate content was dependent on the agricultural production system, while for nitrites, this dependency was less pronounced.

Evaluation of Biological Value and Appraisal of Polyphenols and Glucosinolates from Organic Baby-Leaf Salads as Antioxidants and Antimicrobials against Important Human Pathogenic Bacteria

The present investigation has been carried out to investigate the biological role of four different types of baby-leaf salads and to study their potential as natural sources of antioxidants and antimicrobials against several isolates from important human pathogenic bacteria. Four single types of salads (green lettuce, red lettuce, rucola and watercress) and two mixtures [(1) red lettuce+green lettuce; (2) green lettuce + red lettuce + watercress + rucola] were assayed. The HPLC analysis revealed interesting levels of polyphenols and glucosinolates. The results showed a significant variation (p < 0.05) of polyphenols and glucosinolates with plant material. Nine different types of polyphenols grouped in three major classes were found: gallic acid, chlorogenic acid, caffeic acid and dicaffeoyltartaric acid (phenolic acids); quercitin-3-O-rutinoside, quercitin-3-O-rhamnoside, luteolin-7-O-glucoside and isorhamnetin (flavonoids); and cyanidin-3-glucoside (anthocyanins). Only three different glucosinolates were found: glucoraphanin; gluconasturtiin and 4-methoxy-glucobrassicin. A positive correlation was detected between polyphenol contents and antioxidant activity. Red lettuce and mixture 1 were the baby-leaf salads with the highest antioxidant potential. As for the antimicrobial activity, the results showed a selective effect of chemicals against Gram-positive and Gram-negative bacteria and Enterococcus faecalis and Staphylococcus aureus were the bacteria most affected by the phytochemicals. Based on the results achieved baby-leaf salads represent an important source of natural antioxidants and antimicrobial substances.

Effect of Harvest Year and Altitude on Nutritional and Biometric Characteristics of Blueberry Cultivars

In recent years the consumption of small fruits has increased continuously and knowledge about the more suitable production requirements is essential. This study aims to evaluate the influence of harvest year and altitude on chemical composition of four blueberry cultivars, in order to create rentable opportunities for producers and minimize eventual losses in quality fruits. Dry mass, protein, fat, energy, free sugars, organic acids, and vitamin C contents were determined using HPLC-UV-DAD and spectrophotometric methods. Differences () in the concentrations of free sugars, organic acids, and vitamin C were found among years, while the altitude had no () influence. Citric acid was the main organic acid and fructose the most abundant sugar in blueberries. Fruits of “Ozarkblue” had the highest mass and volume whilst the “Bluecrop” was the cultivar with highest crude protein and fat contents. “Goldtraube” showed the highest content of sucrose and organic acids and “Duke” had the highest content of fructose.

Phytochemical Composition and Antibacterial Activity of Hydroalcoholic Extracts of Pterospartum tridentatum and Mentha pulegium against Staphylococcus aureus Isolates

Pterospartum tridentatum and Mentha pulegium are largely used in Portuguese folk medicine to treat several human disorders and inflammatory processes but without any consistent evidence for those beneficial pointed properties. Thus, the aim of the current work is to evaluate its benefits and phytochemicals related to those beneficial properties. A distinct polyphenol profile between P. tridentatum and M. pulegium was found. Taxifolin, myricetin, ginestin, ginestein, and ginestein derivatives, biochanin A-glucoside, and biochanin A were identified in P. tridentatum, whilst in M. pulegium the luteolin-7-rutinoside, diosmin, and apigenin and respective derivatives were most representative polyphenols. These variations had implications in the antiradical and antibacterial activity and the P. tridentatum exhibited the highest antibacterial activity against methicillin-resistant and methicillin-sensitive Staphylococcus aureus MSSA, which was mainly dose-dependent. This antibacterial activity seems to be related to high content of flavonols, flavones, and isoflavones, which can act synergistically with each other against this type of bacteria. Our results showed consistent evidence that Pterospartum tridentatum and Mentha pulegium are an important reservoir of phytochemicals with antiradical activity and antibacterial capacity and thus they might be used in a preventive way or in a combined pharmaceutical and antibiotic therapy against pathogenic bacteria.

Effects of post-harvest storage conditions on the levels of glucosinolates in broccoli sprouts (Brassica oleracea var. italica) grown under different temperature regimes

Summary Broccoli sprouts have been recognised as a rich source of glucosinolates, particularly 4-methylsulphinylbutyl glucosinolate, the precursor of the potent anti-cancer compound, sulphoraphane. Previous results have shown that temperature can significantly affect the levels of glucosinolates. In this study, we showed how sprout age and storage temperature affected glucosinolate levels in broccoli sprouts grown under different temperature regimes. Experiments were conducted in growth cabinets with day/night temperature regimes of 30°/15°C, 22°/15°C and 18°/12°C. At 9, 10 and 11 d after sowing in the first temperature regime, 10, 11 and 12 d in the second, and 12, 13 and 14 in the third, sprouts were submitted to 4°C or 20°C to simulate refrigerated and room temperature storage. Sampling was done after 1 d or 2 d of exposure to these conditions. The results showed that total glucosinolate levels and the potential health effects of broccoli sprouts depended on the growth temperature regime (P < 0.05), the age of the sprouts (P < 0.001), and the storage conditions (P < 0.01). The highest total glucosinolate levels (65.7 µmoles g–1 dry weight) were obtained under the 30º/15°C temperature regime for the youngest sprouts (harvested 9 d after emergence), after being submitted to a storage temperature of 4°C for 24 h. However, these levels were much lower than in 3-d-old sprouts. Consuming old sprouts provides less health-protective effects due to reduced levels of glucosinolates.

Screening of Polyphenol Composition and Antiradical Capacity of Wild Erica arborea: A Native Plant Species from the Portuguese Flora

With this study, we aimed to determine the polyphenol composition and antiradical activity of activity of Erica arborea a native plant species from the Portuguese and Mediterranean flora and often reported as having important bioactivities, but without consistent scientific evidences. The analysis of polyphenol profile and content was performed by HPLC-DAD/UV-Vis and in vitro bioassay of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) method was used to evaluate the radical scavenging activity. The HPLC analysis showed a great diversity of compounds. E. arborea presented high contents in flavonols (52%) and flavanols (25%) and the average content of antiradical activity higher than 85%. The polyphenols identified are often associated by literature as having preventive properties and protective effect against of degenerative and inflammatory processes, thus, our findings confirm the empirical health properties often associated to this endemic plant. Therefore, based in our study the E. arborea, can be used to extract and purify phytochemicals with potentially beneficial effects on health.