Search Results

You are looking at 71 - 80 of 410 items for :

  • "polyphenols" x
  • Refine by Access: All x
Clear All
Free access

Jafar Milani*

Phenolic compounds and polyphenol oxidase (ppo) activity in five apple cultivars were assessed in relation tobrowning susceptibility. The degree of browning was determined by measuring brown pigments in homogenised pulp. The analysis variance of the browning rate, polyphenol content and ppo activity showed that only the effect of cultivar was significant while the interaction of location and cultivar not significant. Comparison of means (Duncan) classified the cultivars in view of browning rate in three groups (P < 0.01): Strong (Red Delicious), weak (Arangeh and Granny Smith), and mid (Golden Delicious). Arangeh was the superior variety due to its highest total soluble solids and lowest browning rate.

Open access

Claudia A. Espinosa-Leal and Silverio Garcia-Lara

culture of krantz aloe ( Bedini et al., 2009 ; Cardarelli et al., 2017 ; Kawai et al., 1993 ), the establishment of cultures from plant explants has proved difficult because of the long response times of the explants and their release of polyphenols

Free access

Keri L. Andersen, Susan L. Cuppett, Ellen T. Paparozzi, and Paul E. Read

Phenolic levels have been analyzed in several grape cultivars that are suited for growing in southeastern Nebraska. The phenolic levels of these cultivars are not known to have been previously published. The polyphenol content of fruits and fruit products such as wine have been shown to be directly correlated to the antioxidant potential of the product. Antioxidants help to prevent the effects of aging and age-associated diseases. The grape cultivars in the study are grown primarily for wine production, but also as fresh table grapes and for making juice and jellies. The total phenolic content is being analyzed by the Folin-Ciocalteu method. Of the red grapes, `St. Croix' and `Frontenac' have the highest levels of polyphenols, followed by `Chambourcin' and `deChaunac', with levels varying from 1.4–4.9 mg·g-1 (polyphenols/grape), measured as gallic acid equivalents (GAE). The white grapes `Vignoles' and `LaCrosse' have total phenolic levels of 1.4 to 2.2 mg·g-1 (polyphenols/grape), also measured as gallic acid equivalents (GAE).

Free access

Lajos Helyes, Zoltán Pék, and Andrea Lugasi

Soluble solids (Brixo), carbohydrate, organic acid, lycopene, polyphenols and HMF content of indeterminate round type tomato Lemance F1 fruits were measured in six ripeness stages from mature green to deep red stage. Color of fruits was determined by CIELab system. The L*, a*, b* values were received directly and used to calculate from which the a*/b* ratio was calculated. The Brixo, carbohydrate, lycopene and HMF content were the highest in the deep red stage. Carbohydrate contents constitute nearly 50% of the Brixo. The mature green stage had the lowest acid content but in subsequent stages it was fundamentally unchanged. Polyphenol content changed little during fruit ripening. Lycopene content changed significantly during maturation and accumulated mainly in the deep red stage. Analyses showed that a*/b* was closely correlated with lycopene and can be used to characterize stages of maturity in fresh tomatoes.

Free access

Amnon Levi, Glenn A. Galau, and Hazel Y. Wetzstein

A simple and efficient protocol is reported for the isolation of RNA from embryos and leaves of pecan [Carya illinoinensis (Wangenh.) K. Koch]. The method relies on suppression of the polyphenols from interaction with the RNA and their rapid removal from the homogenate by chloroform extraction. This method produced abundant amounts of high-quality RNA. This protocol is likely to be useful for Juglandaceous species and other recalcitrant plants with high levels of phenolic compounds.

Free access

M. Radi, M. Mahrouz, A. Jaouad, M. Tacchini, S. Aubert, M. Hugues, and M.J. Amiot

Phenolic composition and susceptibility to browning were determined for nine apricot (Prunus armeniaca L.) cultivars. Chlorogenic and neochlorogenic acids, (+)-catechin and (-)-epicatechin, and rutin (or quercetin-3-rutinoside) were the major phenolic compounds in apricots. In addition to these compounds, other quercetin-3-glycosides and procyanidins have been detected. Chlorogenic acid content decreased rapidly during enzymatic browning, but the susceptibility to browning seemed to be more strongly correlated with the initial amount of flavan-3-ols (defined as catechin monomers and procyanidins). As chlorogenic acid is certainly the best substrate for polyphenol oxidase, the development of brown pigments depended mainly on the flavan-3-ol content.

Free access

Ena Akamatsu, Takanori Kai, Hideaki Hirabaru, Chizuko Yukizaki, Miho Sakai, Hirofumi Uto, Hirohito Tsubouchi, and Hisato Kunitake

Blueberry (Vaccinium sp.) fruits contain high concentrations of polyphenols such as anthocyanin. It is well known that polyphenols have antioxidant activity, so it is likely that the fruit has a possible preventative effect against several diseases like cancer. However, only a few reports so far have studied the human health benefits of the leaves. In this study, the antioxidant activity and antiviral effects of blueberry leaves were investigated. The leaves of three groups of blueberry, northern highbush blueberry (NHB), southern highbush blueberry (SHB), and rabbiteye blueberry (REB), were examined. These leaves were harvested in July and extracted with 80% ethanol. Samples were analyzed for antioxidant activity (DPPH radical scavenging activity) and antiviral activity against hepatitis C virus using the replicon cell assay (Lomann et al., 1999). The antioxidant activity showed significant variability between cultivars and species, with REB having about two times the activity of NHB and SHB. Antiviral activity was observed in the extracts of the leaves and the fruit, and the activity of the leaves was higher than that of the fruit. Among the cultivars and species evaluated, the antiviral activity of REB was higher than that of NHB and SHB. In addition, we discovered a positive correlation (r=0.68) between the antioxidant activity and the antiviral activity, using the leaves of hybrid seedlings of REB. Therefore, it is possible to speculate that the antiviral activity bears some relation to the antioxidant activity.

Free access

R.C. Gueldner, I.E. Yates, C.C. Reilly, B.W. Wood, and M.T. Smith

Polyphenols were analyzed in expanding buds and developing leaves of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars with varying responses to Cladosporium caryigenum (Ell. et Lang. Gottwald), the organism causing scab. Plant tissue extracts were examined by high-performance liquid chromatography using a water: methanol gradient to separate polyphenolic components on a C-18 reversed phase column. A diode-array detector was used to identify profile components by retention times and computer matching of ultraviolet spectra to standard compounds in a library. Concentrations of these polyphenols were compared throughout the growing season in leaves of pecan cultivars with low (`Elliott'), intermediate (`Stuart'), and high (`Wichita') susceptibility to scab; during susceptibility to infection by Cladosporium caryigenum from 16 cultivars; and in `Wichita' leaf discs with and without scab lesions. The major polyphenolic constituent of tissues for all cultivars was identified as hydrojuglone glucoside, which was detected in intact buds and leaves throughout the growing season. Hydrojuglone glucoside concentration increased concomitantly with leaf expansion and then declined slowly. Juglone was barely, if at all, detectable, regardless of leaf age. No correlation was found between cultivar susceptibility to pecan scab and the levels of either juglone or hydrojuglone glucoside in the healthy leaves of 16 cultivars. Leaf tissue with scab lesions had significantly higher juglone and hydrojuglone glucoside levels than leaf discs without scab lesions. Chemical names used: 4-8-dihydroxy-1-naphthyl b-d-glucopyranoside (hydrojuglone glucoside); 1,5-hydroxy-naphthoquinone (juglone).

Free access

S. Y. Wang, J. L. Maas, E. M. Daniel, and G. J. Galletta

Ellagic acid (EA) a naturally occurring polyphenol in many fruit and nut crops, is a putative inhibitor of certain chemically-induced cancers. Improved methods of extraction, detection and quantification are essential for accurate determination of EA for plant physiological and genetic studies and animal nutrition and chemopreventative studies. Column (C18) preconditioning significantly reduced column retention of EA. An ammonium phosphate/methanol solvent system was used in preference to sodium phosphate/methanol. Fruit sample determinations were 10-100 times higher than previously reported, due to the improvements in efficiency of these methods. EA levels (mg/g dry wt) were: strawberry pulp (1.55), achene (8.46), root (1.55), crown (3.32) and leaf (14.27); blackberry pulp (,2.43) and seed (3.37); and cranberry skin (1.06), pulp (0.31), seed (0.69), leaf (4.10).

Free access

S.J.R. Underhill and C. Critchley

Mature lychee (Litchi chinensis Sonn.) fruit were heat-treated at 60C for 10 min to study heat-induced pericarp browning. Polyphenol oxidase (EC 1.10.3.2) activity of the pericarp increased immediately, corresponding with rapid anthocyanin degradation, Tissue browning was observed 2 min after heating, with pigmentation distributed uniformly throughout the pericarp. The distribution of brown pigments was different than the highly localized browning observed under ambient desiccation. Although both ambient and heat-induced pericarp browning are visually similar, the anatomical distribution of brown pigmentation is quite distinct. The distribution of brown pigmentation was not consistent with anthocyanin localization. Following ambient desiccation, the mesocarp became colorless even though this represented the greatest concentration of pigment. Browning caused by heating may result from nonselective degradation of a range of compounds, including anthocyanin.