Levels Of Proanthocyanidins Research Articles

Stability of phenolic and protein measures in excised oak foliage

The stability of protein and phenolic measures in excised foliage from two oak species was measured under conditions that simulated the handling and treatment of foliage during insect rearing trials. Excised foliage kept hydrated under refrigeration or insect-rearing conditions maintained stable levels of protein content, proanthocyanidins, gallotannins, total phenolics, and protein-binding capacity for up to 48 hr following field sampling. Measures of protein content, total phenolics, protein-binding capacity, and proanthocyanidins were significantly greater 48-72 hr after field sampling, followed by declines to near field levels within 120 hr.

Fodder tree and straw diets for sheep: intake, growth, digestibility and the effects of phenolics on nitrogen utilisation

Intake, growth, digestibility and nitrogen (N) utilisation by sheep were investigated for seven experimental diets which consisted of teff straw ( Eragrostis abyssinica) fed ad libitum with phyllodes of Acacia cyanophylla (Diet 10, fruits of Acacia sieberiana (Diet 2), leaves of Acacia seyal (Diet 3) and Sesbania sesban (Diet 4), vetch hay ( Vicia dasycarpa) (Diet 5) and noug cake ( Guizotia abyssinica) (Diet 6). Diet 7 included urea to provide an intake of 1% N. A. cyanophylla had a high fibre and lignin content due to a high level of proanthocyanidins (condensed tannins). The three acacias had the highest content of soluble phenolics and insoluble proanthocyanidins. S. sesban had the lowest content of fibre and polyphenols. Diets containing acacias had the highest levels of feed refusals and the lowest intake of teff straw. However, the intake of A. seyal increased over time. Sheep fed S. sesban had the highest intake of teff straw. The growth rate was highest for Diets 4 and 5, reflecting high intakes, while sheep eating Diet 1 lost weight. Growth rates for sheep fed A. seyal were similar to those of sheep fed S. sesban and vetch hay during the last 7 weeks of the growth trial after intake had increased. Digestibility of fibre was lowest for diets containing acacias. Proanthocyanidins in A. cyanophylla may have complexed protein in the digestive tract causing negative digestion coefficients for lignin and N insoluble in neutral detergent. The content of faecal N that was soluble in neutral detergent was highest for sheep fed A. seyal, indicating higher excretion of microbial and endogenous N in the faeces. Urinary N loss was lowest and faecal N loss was highest for diets containing acacias. N balance was positive for sheep fed all diets except A. cyanophylla. The N fraction in diets containing acacias was not nutritionally uniform because of the influence of polyphenols on protein digestion and metabolism.

グアバに含まれるポリフェノールの消長とその特性

With the purpose of utilizing tropical and substropical fruits more effectively, abundant polyphenols found in guava (Psidium guajava L.) fruit and leaves were examined seasonally in both qualitative and quantitative aspects.1) The method reported by Peri and Pompei was recognized to be highly useful for determining various polyphenols in crude extracts of guava.2) Young guava fruit (picked on 18th August and weighting 2.9g) contained 620mg of total polyphenols per 100g fresh weight and 68% of the polyphenols was shown to be condensed tannin. Ass the fruit grew up, their contents of condensed tannin decreased remarkably.3) Proanthocyanidin levels in the guava fruit also decreased with the increase in fruit weight from August to October.4) Gel permeation chromatographic analyses of polyphenols suggest that high molecular weight polyphenols of more than 14, 000 disappeared with fruit development.5) The polyphenol level of guava picked on 3rd August was about 10 times that of young fruit (picked on 18th August) and 84% of the total polyphenols was found to be condensed tannin. The levels decreased markedly at the late of August.6) (+)-Catechin and (+)-gallocatechin were identified by a reversed phase HPLC in the extracts of guava fruit and leaves.These results indicate that a large percentage of polyphenols in guava fruit and leaves is a type of flavans, especially proanthocyanidin heteropolymers that are composed of (+)-catechin and (+)-gallocatechin, and these compounds decrease remarkably at the early stage of fruit development or at the late of August in the leaves.

Gravimetric determination of soluble phenolics including tannins from leaves by precipitation with trivalent ytterbium

AbstractA method for the gravimetric determination of soluble phenolics based on precipitation with trivalent ytterbium is described. Solutions of ytterbium‐precipitated phenolics can be prepared in order to study u.v. absorbance, colorimetric assays for phenolics, protein precipitation and cellulase inhibition. The method was applied to mature leaves of 10 East African browse species in the diets of goats and camels. There was a large range in ytterbium‐precipitated phenolics (Yb‐ppt), from 50% dry matter (DM) in Acacia nilotica to less than 15% in Acacia brevispica and Cadaba farinosa. Results from u.v. absorbance and the Folin‐Ciocalteu assay on solutions of ytterbium‐precipitated phenolics indicated that ytterbium precipitates many types of phenolics including proanthocyanidins. The vanillin‐HCl and n‐butanol‐HCl assays for proanthocyanidins separated the samples into two groups with high or low levels. The group with high levels of proanthocyanidins had greater protein precipitation capacity and cellulase inhibition at similar amounts of Yb‐ppt. The results indicate that the method may be useful in nutritional studies involving browse and other forages. Gravimetric analysis avoids problems associated with colorimetric assays because it does not rely on the use of standards. The preparation of solutions of Yb‐precipitated phenolics allows direct comparison between amount and nutritional effects such as protein precipitation and enzyme inhibition.

Variability in accumulation of proanthocyanidins (condensed tannins) in needles of Douglas-fir (Pseudotsuga menziesii) following long-term budworm defoliation

Long-term defoliation by budworms was associated with higher levels of soluble proanthocyanidins in the current year needles of Douglas-fir trees. The proanthocyanidin contents of needles from defoliated Douglas-fir trees were considerably more variable than those levels of undefoliated ones. The increased mean and variability of proanthocyanidin levels following defoliation may have interesting ecological consequences for Douglas-fir and its defoliators.

Enzyme activities and polyphenols related to mesocarp discolouration of avocado fruit

Avocado fruit showing severe symptoms of the mesocarp discolouration disorder exhibited significantly higher extractable activities of soluble polyphenol oxidase and peroxidase, as well as higher levels of total phenols, hydroxycinnamic acids and proanthocyanidins, when compared to healthy fruit. However, l-phenylalanine ammonia-lyase activity was very variable, and no significant differences were observed between healthy and affected fruit. Extraction of healthy, but not severely affected, fruit in the presence of 0.1 % SDS resulted in increased polyphenol oxidase activity reflecting the release of bound and/or latent enzyme. Qualitative differences between healthy and affected fruit included different patterns of polyphenol oxidase multiple forms and different polyphenol profiles. The pattern of polyphenol oxidase multiple forms from SDS-extracted healthy fruit was similar to that from mildly affected fruit not extracted with detergent.

Condensed proanthocyanidins of fababeans.

AbstractCondensed proanthocyanidins were extracted from fababean hulls with water. The aqueous extract, after deproteinisation by freezing, thawing and acetone precipitation, was purified by chromatography using Sephadex LH20 gel and 95% ethanol developing solvent. Gradient chromatography of the purified condensed proanthocyanidins using 95% ethanol‐(50% v/v)acetone‐water with a Sephadex LH20 column yielded two peaks when the column effluent was monitored at 400 nm. Chromatographic behaviour before and after oxygen treatment indicated certain structural differences between fractions collected under the major peak. There were also considerable differences between the chromatographic properties of material collected from under the major peak and under the minor peak. Solvolysis experiments on the various fractions yielded differences in delphinidin: cyanidin and delphinidin: phlobaphene ratios. There were also differences in ‘tannin’ contents (determined by acidified vanillin methods) and all these differences confirmed that there were structural dissimilarities between the fractions. Tannin determinations made on the hulls of seven different cultivars of fababeans indicated condensed proanthocyanidin levels between 0–6%.