Sedef Nehir El

Olive tree (Olea europaea) leaves: potential beneficial effects on human health

Olive tree (Olea europaea L.) leaves have been widely used in traditional remedies in European and Mediterranean countries such as Greece, Spain, Italy, France, Turkey, Israel, Morocco, and Tunisia. They have been used in the human diet as an extract, an herbal tea, and a powder, and they contain many potentially bioactive compounds that may have antioxidant, antihypertensive, antiatherogenic, anti-inflammatory, hypoglycemic, and hypocholesterolemic properties. One of these potentially bioactive compounds is the secoiridoid oleuropein, which can constitute up to 6-9% of dry matter in the leaves. Other bioactive components found in olive leaves include related secoiridoids, flavonoids, and triterpenes. The evidence supporting the potentially beneficial effects of olive leaves on human health are presented in this brief review.

Antioxidant activity of some foods containing phenolic compounds

This study was designed to determine the total phenols (TP) and total antioxidant activity (TAA) of some liquid and solid plant foods that are commonly consumed in Turkey. Total phenols were analysed according to the Folin-Ciocalteu method and antioxidant activities of these compounds in aqueous phase were assessed by measuring their direct ABTS.- radical scavenging abilities. Total phenols varied from 68 to 4162 mg/l for liquid foods and from 735 to 3994 mg/kg for solid foods. TAA of liquid and solid foods ranged between 0.61-6.78 mM and 0.63-8.62 mM, respectively. Total antioxidant activities of foods were well correlated with total phenols (r2 = 0.95). According to content of total phenols per serving, liquid foods were in the order of black tea > instant coffee > coke > red wine > violet carrot juice > apricot nectar > Turkish coffee > grape molasses > sage > white wine > linden flower, and solid foods were in the order of red grape > raisins > tarhana > dried black plum > dried apricot > grape > fresh paprika > fresh black plum > Urtica sp. > cherry > fresh apricot > paprika pickle > paprika paste.This study was designed to determine the total phenols (TP) and total antioxidant activity (TAA) of some liquid and solid plant foods that are commonly consumed in Turkey. Total phenols were analysed according to the Folin-Ciocalteu method and antioxidant activities of these compounds in aqueous phase were assessed by measuring their direct ABTS .– radical scavenging abilities. Total phenols varied from 68 to 4162 mg/l for liquid foods and from 735 to 3994 mg/kg for solid foods. TAA of liquid and solid foods ranged between 0.61-6.78 mM and 0.63-8.62 mM, respectively. Total antioxidant activities of foods were well correlated with total phenols (r 2 = 0.95). According to content of total phenols per serving, liquid foods were in the order of black tea > instant coffee > coke > red wine > violet carrot juice > apricot nectar > Turkish coffee > grape molasses > sage > white wine > linden flower, and solid foods were in the order of red grape > raisins > tarhana > dried black plum > dried apricot > grape > fresh paprika > fresh black plum > Urtica sp. > cherry > fresh apricot > paprika pickle > paprika paste.

Radical scavenging and iron-chelating activities of some greens used as traditional dishes in Mediterranean diet

This study aimed at evaluating the antioxidative activity of nine different families of greens. Raphanus raphanistrum (wild radish), Anchusa azurea (bugloss), Daucus carota (wild carrot), Sonchus oleraceus (sowthistle), Papaver rhoeas (corn poppy), Malva sylvestris (blue mallow), Foeniculum vulgare (fennel), Cichorium intybus (chicory) and Salicornia europaea (jointed glasswort) are native to the Mediterranean and are commonly consumed as a salad or an ingredient in some recipes. The antioxidative activities, including the radical scavenging effects, inhibition of hydrogen peroxide (H2O2), and Fe2+-chelating activity, were studied. All samples showed antioxidant activity as a radical scavenger in the experiment using the DPPH• radical. The ratio between the slopes of the kinetic model was used to compare antioxidant efficiency of different greens. Greens also possessed antioxidative activity toward H2O2. Especially, greens exhibited a marked scavenging effect on H2O2 at 0.2 g/ml concentration. The Fe2+ ion-chelating activities of the samples except jointed glasswort were greater than 70%. The antioxidant activity of samples with different methods based on the inhibition of different reactions could not be compared. The current dietary guidelines include recommendations for an increase in the consumption of plant foods. Greens should provide an optimal supply of antioxidant substances in the diet.

In Vitro Models for Studying Secondary Plant Metabolite Digestion and Bioaccessibility

There is an increased interest in secondary plant metabolites, such as polyphenols and carotenoids, due to their proposed health benefits. Much attention has focused on their bioavailability, a prerequisite for further physiological functions. As human studies are time consuming, costly, and restricted by ethical concerns, in vitro models for investigating the effects of digestion on these compounds have been developed and employed to predict their release from the food matrix, bioaccessibility, and assess changes in their profiles prior to absorption. Most typically, models simulate digestion in the oral cavity, the stomach, the small intestine, and, occasionally, the large intestine. A plethora of models have been reported, the choice mostly driven by the type of phytochemical studied, whether the purpose is screening or studying under close physiological conditions, and the availability of the model systems. Unfortunately, the diversity of model conditions has hampered the ability to compare results across different studies. For example, there is substantial variability in the time of digestion, concentrations of salts, enzymes, and bile acids used, pH, the inclusion of various digestion stages; and whether chosen conditions are static (with fixed concentrations of enzymes, bile salts, digesta, and so on) or dynamic (varying concentrations of these constituents). This review presents an overview of models that have been employed to study the digestion of both lipophilic and hydrophilic phytochemicals, comparing digestive conditions in vitro and in vivo and, finally, suggests a set of parameters for static models that resemble physiological conditions.

Mind the gap—deficits in our knowledge of aspects impacting the bioavailability of phytochemicals and their metabolites—a position paper focusing on carotenoids and polyphenols

Various secondary plant metabolites or phytochemicals, including polyphenols and carotenoids, have been associated with a variety of health benefits, such as reduced incidence of type 2 diabetes, cardiovascular diseases, and several types of cancer, most likely due to their involvement in ameliorating inflammation and oxidative stress. However, discrepancies exist between their putative effects when comparing observational and intervention studies, especially when using pure compounds. These discrepancies may in part be explained by differences in intake levels and their bioavailability. Prior to exerting their bioactivity, these compounds must be made bioavailable, and considerable differences may arise due to their matrix release, changes during digestion, uptake, metabolism, and biodistribution, even before considering dose‐ and host‐related factors. Though many insights have been gained on factors affecting secondary plant metabolite bioavailability, many gaps still exist in our knowledge. In this position paper, we highlight several major gaps in our understanding of phytochemical bioavailability, including effects of food processing, changes during digestion, involvement of cellular transporters in influx/efflux through the gastrointestinal epithelium, changes during colonic fermentation, and their phase I and phase II metabolism following absorption.

Quercetin, luteolin, apigenin and kaempferol contents of some foods

Quercetin, luteolin, apigenin and kaempferol contents of Urtica sp., Rosa cannina (rosehip), Salvia officinalis (sage), Tilia platyphyllos (linden flower), black tea, Daucus carota L. spp sativus (violet carrot juice), grape molasses, honey and tarhana were determined by HPLC with UV detection. Consumption of the samples was assessed using a food frequency questionnaire method. One hundred healthy volunteers were asked to state the number of times on average per day, week or month they consumed each item over the last 6 months. Quercetin was determined in all samples except honey, whereas luteolin was determined only in sage. Kaempferol was determined in black tea, linden flower and honey samples, and apigenin was determined in honey and Urtica sp. Quercetin intake by the consumption of tea, linden flower, sage rosehip, violet carrot juice, grape molasses, tarhana and juice of Urtica sp. were estimated as 4.2–25, 2.6, 3.3, and 2.0 μg/day, 1.67 mg/day, 1.70 mg/day, 1.78 mg/month and 21.75–65.25 μg/month, respectively. Luteolin intake by the consumption of sage was estimated as 1.32 μg/day. Apigenin intakes by the consumption of honey and juice of Urtica sp. were estimated as 2.34 mg/day and 3.58–10.73 mg/month, respectively. Kaempferol intakes of the participants from tea, linden flower and honey were estimated as 13.2–79.2, 13.56 and 190 μg/day respectively. ©

Role of polysaccharides in food, digestion, and health

ABSTRACT Polysaccharides derived from plant foods are major components of the human diet, with limited contributions of related components from fungal and algal sources. In particular, starch and other storage carbohydrates are the major sources of energy in all diets, while cell wall polysaccharides are the major components of dietary fiber. We review the role of these components in the human diet, including their structure and distribution, their modification during food processing and effects on functional properties, their behavior in the gastrointestinal tract, and their contribution to healthy diets.

Production of resistant starch from taro (Colocasia esculenta L. Schott) corm and determination of its effects on health by in vitro methods

The aim of the study was the production of resistant starch from taro (Colocasia esculenta L. Schott) corm and determination of its effects on health by in vitro methods. Starch was isolated from taro corms with 98% purity, and 10.4±0.5% amylose content. By application of heating, autoclaving, enzymatic debranching, retrogradation, and drying processes to taro starch for two times, resistant starch (RS) content was increased 16 fold (35.1±1.9%, dry basis). The expected glycemic index (eGI) of taro starch and taro resistant starch was determined as 60.6±0.5 and 51.9±0.9, respectively and the decrease in the glycemic index of taro resistant starch was found as statistically significant (P<0.05). The in vitro binding of bile acids by taro starch and taro resistant starch relative to cholesterol decreasing drug cholestyramine were 5.2±0.2% and 7.6±1.7%, respectively.

Determination of glycemic index for some breads

Abstract Glucose-responses and glycemic indices of standard bread, rye bread and mixed bread were studied with 10 healthy subjects. Incremental areas of blood glucose (above fasting levels) were calculated as 81, 58 and 46 mmol/liter×120 min GI values determined as 100, 72, 57 for standard bread, rye bread and mixed bread, respectively. The area under the glucose-response curve and GI value of standard bread were significantly higher than rye bread and mixed bread ( p

In vitro determination of calcium bioavailability of milk, dairy products and infant formulas.

In this study, the aim was to determine the in vitro calcium bioavailability of different dairy products and to investigate the effect of dry matter, fat, acidity and calcium content on calcium bioavailability of the products. For this purpose, the dry matter, fat, acidity and calcium content of different kinds of milk, yogurt, cheese and infant formulas were analysed. Then, calcium bioavailability of products was determined by an in vitro method that involves simulating gastrointestinal digestion of the product with pepsin–HCl and pancreatin–biliary salts, and then measuring the fraction of element that dialyses through a membrane of a certain pore size. Each of the product groups was examined statistically and no difference was found among milk, yogurt and infant formula groups in terms of calcium bioavailability. However, there were differences among cheese kinds according to the results of the Duncan test; all cheese kinds were considerably different from each other (P < 0.05). Moreover, it was found that calcium, dry matter, fat content and acidity did not affect the calcium bioavailability (P < 0.05). According to the results of statistical analysis that was applied to all product groups, it was found that the yogurt group was different from the other products and that the acidity affected calcium bioavailability (P < 0.05).