Studies on the extraction and characterization of pectin and bitter principles from New Zealand grapefruit and Philippine calamansi : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University

A study was conducted to determine the presence of bitter components in NZ grapefruit and Philippine calamansi; describe the effect of maturity on the bitter components and other chemical constituents of grapefruit; reduce the bitterness of grapefruit juice by adsorption on polyvinylpyrrolidone; and to extract and characterize pectin from grapefruit peel. Naringin (995 PPm), narirutin (187 ppm), and limonoids (7.9 ppm) were detected in NZ grapefruit juice concentrate (27° Brix). Naringin was not detected in the calamansi juice, and limonin was detected at the level of 10.5 ppm in juice containing 5% crushed seeds. Maturation of the grapefruit caused an increase in pH from 3.00 to 3.50, an increase in total soluble solids from 10.8 to 14.4 with a decline to 13.5° Brix later in the season, a steady fall in acidity from 2.50 to 1.31 g citric acid/100 mL, and a continuous rise in the Brix/acid ratio from 4.2 to 10.3. Juice yield fluctuated throughout the season. Ascorbic acid remained fairly steady in the early and mid-season fruit but decreased in the late-season fruit. Naringin content was highest at the beginning of the season and fluctuated throughout the season. Naringin content in the grapefruit peel remained constant as the fruit matured. Narirutin was detected in the early-season fruit but disappeared later in the season. Limonoid content in both unpasteurized and pasteurized juices decreased with ripening. The use of polyvinylpyrrolidone significantly reduced naringin in grapefruit juice by up to 78.1% and limonin by up to 17.5% depending on the amount and reaction time of the adsorbent. A loss of 23.1% in ascorbic acid occurred with 5% PVP with a reaction time of 1 h. Pectin extraction at 85°C and the use of acidified isopropyl alcohol yielded a product with the following characteristics: 8.9% yield; 1.3% moisture content; 1.9% ash; 759 equivalent weight; 9.2% methoxyl content; 82.2% anhydrogalacturonic acid; 63.2% degree of esterification; 4.2 intrinsic viscosity; 89,362 molecular weight and setting time of 0.55 minute

New potential sodium-glucose co-transporters sugar-based inhibitors for the treatment of diabetes

Tese de doutoramento, Química (Química Orgânica), Universidade de Lisboa, Faculdade de Ciências, 2015A small library of C-glucosyl dihydrochalcones and their aglycones, chalcones and dihydrochalcones, were synthesized aiming at preparing new C-glucosyl analogues of phlorizin, a well-known non-selective sodium-glucose co-transporter inhibitor, bearing different substituents on the dihydrochalcone moiety. Chalcones were prepared by conventional aldol condensation methods and also by microwave-assisted synthesis. The yields using the latter were relatively similar to those obtained by conventional methods (70-95%) but it was possible to decrease the reaction time from 24 to 1 h. Dihydrochalcones were obtained in 90-99% by in situ hydrogenation using the system Et3SiH/Pd-C, a method that was used for the first time in this family of compounds, that revealed very promising and simple to run. C-Glucosylation of dihydrochalcones was investigated with the catalyst TMSOTf and using 2,3,4,6-tetra-O-benzyl--D-glucopyranose as glycosyl donor, instead of a donor with a more effective leaving group at the anomeric position, e.g. trichloroacetimidate, to decrease the number of reaction steps. The C-glucosylation proceeded smoothly with yields ranging from 40-47% and the following debenzylation by in situ hydrogenation (80- 98% yield) afforded the C-glucosyl dihydrochalcones. Cytoxicity of chalcones, dihydrochalcones and C-glucosyl dihydrochalcones was evaluated in HEK293 cells and no significant toxicity was found for those compounds bearing three hydroxyl groups in ring A. Conversely, chalcones and dihydrochalcones bearing one or two hydroxyl groups on ring B showed significant cytoxicity in the same cell line. Two stable cell lines were generated, HEK293-SGLT1 and HEK293-SGLT2, and the two stable clones showing the highest expression by Western Blot and RT-PCR were used to evaluate the inhibitory properties of chalcones, dihydrochalcones, and C-glucosyl dihydrochalcones as well as to determine their IC50 values towards SGLT1 and SGLT2 proteins. Results showed that chalcones and dihydrochalcones are able to partially inhibit SGLT1 and SGLT2 without showing significant selectivity towards with SGLT1 or SGLT2. On the other hand, C-glucosyl dihydrochalcones inhibit both SGLT1 and SGLT2 at 100 M but showed a > 500-fold SGLT2 selectivity. IC50 of these molecules were much better than those of phlorizin, but slightly worse than the commercial drug dapagliflozin. Nevertheless, changing from the O-glucoside phlorizin to its C-glucosyl analog, it was possible to increase its inhibitory ability as well its selectivity

Chalcones and Dihydrochalcones Augment TRAIL-Mediated Apoptosis in Prostate Cancer Cells

Chalcones and dihydrochalcones exhibit chemopreventive and antitumor activity. TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) is a natural endogenous anticancer agent. We examined the cytotoxic and apoptotic effect of chalcones and dihydrochalcones on TRAIL-mediated apoptosis in LNCaP prostate cancer cells. The cytotoxicity was evaluated by the MTT and LDH assays. The apoptosis was detected using annexin V-FITC by flow cytometry and fluorescence microscopy. The ΔΨm was evaluated using DePsipher staining by fluorescence microscopy. Our study showed that two tested chalcones (chalcone and 2’,6’dihydroxy-4’-methoxychalcone) and three dihydrochalcones (2’,6’-dihydroxy-4’4-dimethoxydihydrochalcone, 2’,6’-dihydroxy-4’-methoxydihydro- chalcone,  and 2’,4’,6’-trihydroxydihydrochalcone, called phloretin) markedly augmented TRAIL-induced apoptosis and cytotoxicity in LNCaP cells and confirmed the significant role of chalcones in chemoprevention of prostate cancer

The Study of Adsorption Kinetics of Flavan-3-Ols, Dihydrochalcones and Anthocyanins onto Barley β-Glucan

Polyphenols can interact with dietary fibers and these interactions can affect polyphenols bioactivities. The interactions can be studied with the adsorption process, and adsorptions of flavan-3-ols (procyanidin B1, procyanidin B2), dihydrochalcones (phloretin, phloretin-2-glucoside), and anthocyanins (cyanidin-3-glucoside, cyanidin-3-galactoside) onto β-D-glucan from barley were studied in this work. The intention was to reveal the kinetics of the adsorption process. Adsorption was carried out using model solutions at room temperature. The results showed that in the flavan-3-ol group procyanidin B1 showed higher adsorption capacity than procyanidin B2. Phloretin showed a higher adsorption capacity than phloretin-2-glucoside in the dihydrochalcone group and anthocyanins showed similar adsorption capacities. Parameter k1 for all polyphenols was in the range from 0.30 h−1 to 0.93 h−1. Adsorption capacity qe for all polyphenols ranged from 2.90 mmol g−1 to 9.76 mmol g−1, parameter k2 was in the range 70− 225 g mol−1 h−1, and adsorption capacities qe ranged from 3.70 mmol g−1 to 9.90 mmol g−1

Histolocalization and physico-chemical characterization of dihydrochalcones: Insight into the role of apple major flavonoids

Flavonoids, like other metabolites synthesized via the phenylpropanoid pathway, possess a wide range of biological activities including functions in plant development and its interaction with the environment. Dihydrochalcones (mainly phloridzin, sieboldin, trilobatin, phloretin) represent the major flavonoid subgroup in apple green tissues. Although this class of phenolic compounds is found in very large amounts in some tissues (≈200 mg/g of leaf DW), their physiological significance remains unclear. In the present study, we highlight their tissue-specific localization in young growing shoots suggesting a specific role in important physiological processes, most notably in response to biotic stress. Indeed, dihydrochalcones could constitute a basal defense, in particular phloretin which exhibits a strong broad-range bactericidal and fungicidal activity. Our results also indicate that sieboldin forms complexes with iron with strong affinity, reinforcing its antioxidant properties and conferring to this dihydrochalcone a potential for iron seclusion and/or storage. The importance of localization and biochemical properties of dihydrochalcones are discussed in view of the apple tree defense strategy against both biotic and abiotic stresses

DETERMINATION OF POLYPHENOLS BIOACCESSIBILITY BY IN VITRO GASTROINTESTINAL DIGESTION OF APPLE PEEL

Bioaccessible polyphenols represent polyphenols that are released from the food matrix during digestion and become available for absorption. This work aimed to determine the bioaccessible polyphenols from the peel of commercial apple variety ‘Idared’ throughout oral, gastric, and intestinal simulated digestion. Polyphenols were extracted by the means of chemical and enzymatic extraction. In vitro gastrointestinal digestion of the peel of apples was conducted. Polyphenols present in the extracts and oral, gastric, and intestinal digest were analyzed with the use of high-performance liquid chromatography. The amount of polyphenols released during the simulated digestion was lower than the one present in the extracts. Polyphenols bioaccessibility, expressed as a percentage of initial polyphenol concentrations, was 26%, 37%, and 22% for oral, gastric, and intestinal phases, respectively. Flavonols showed to be the most stable group with the intestinal recovery of 34%, followed by phenolic acids (11%) and dihydrochalcones (8%). Flavan-3-ols and anthocyanins were not found in the intestinal phase. These results suggest that polyphenols are released from the peel of apples during digestion and that the amount decreases in the intestines

Polyphenols of Traditional Apple Varieties - The Overview

Apples are one of the most popular foods around the world. However, recently there has been a growing interest in the preservation of traditional apple varieties. This interest has grown due to the studies that suggest that traditional apples contain higher amounts of polyphenolics and antioxidant activity compared to commercial ones. Polyphenolics in apples have gained much attention because of their beneficial effects on human health, and thus they became a quality trait of apples. Traditional apple varieties have the same groups of polyphenols as commercial ones and those are flavan-3-ols, phenolic acids, flavonols, dihydrochalcones, and anthocyanins. However, traditional apple varieties proved to be rich in some individual polyphenolics, such as procyanidins B1, B2, A2, epicatechin, quercetin-3-rutinoside, chlorogenic acid, etc. This chapter is underlying the great potential of traditional apple varieties as a source of some individual polyphenolics and natural antioxidants