Structure-activity relationships in the hydrophobic interactions of polyphenols with cellulose and collagen

Polyphenol interactions with both cellulose and collagen in the solid state have been studied by using chromatography on cellulose and by evaluating the hydrothermal stability of the polyphenol treated sheepskin collagen. Twenty-four polyphenolic compounds were studied, including seven glucose-based gallotannins, five polyalcohol-based gallotannins, and twelve ellagitannins. In the cellulose-polyphenols systems, the polyphenol's affinity to cellulose is positively correlated with their molecular masses, the number of galloyl groups, and their hydrophobicity (logP). The polyphenol treatment increased the hydrothermal stability of collagen samples, and such effects are also positively correlated with the molecular masses, total number of galloyl groups and the hydrophobicity of polyphenols. Ellagitannins showed much weaker interactions with both biopolymers than gallotannins having similar molecular mass, the same number of galloyl groups, and the same number of phenolic hydroxyl groups. It is concluded that, for the polyphenol interactions with both cellulose and collagen, (1) the galloyl group of polyphenols is the functional group; (2) the strength of interactions are positively correlated with molecular size, the number of galloyl groups and the hydrophobicity of polyphenols; (3) the hydrophobic interactions are of great significance; and (4) the interactions are strongly dependent on the flexibility of galloyl groups.     

Can genetically based clines in plant defence explain greater herbivory at higher latitudes?

Greater plant defence is predicted to evolve at lower latitudes in response to increased herbivore pressure. However, recent studies question the generality of this pattern. In this study, we tested for genetically based latitudinal clines in resistance to herbivores and underlying defence traits of Oenothera biennis. We grew plants from 137 populations from across the entire native range of O. biennis. Populations from lower latitudes showed greater resistance to multiple specialist and generalist herbivores. These patterns were associated with an increase in total phenolics at lower latitudes. A significant proportion of the phenolics were driven by the concentrations of two major ellagitannins, which exhibited opposing latitudinal clines. Our analyses suggest that these findings are unlikely to be explained by local adaptation of herbivore populations or genetic variation in phenology. Rather greater herbivory at high latitudes can be explained by latitudinal clines in the evolution of plant defences.     

Polyphenols of Eucalyptus sideroxylon wood

Twenty-three major components were detected in the methanol extractives of the heartwood of Eucalyptus sideroxylon. The components identified include resveratrol, resveratrol-β-glucoside, 3,3′-di- and 3,3′,4-tri-o-methylellagic acids and their glucosides. The 3,3′-di-o-methylellagic acid 4′-glucoside isolated had properties significantly different from those previously reported for this compound. Also present were gailic acid, catechin, ellagic acid, an unidentified stilbene, the ellagitannins D-6 and D-13, polymerized leucocyanidin and an oily material. The sapwood contained gailic acid, small amounts of ellagitannins and ellagic acids and traces of other components. The heartwood extractives of related eucalypt species were also examined.     

Aphid feeding deterrency of ellagitannins, their phenolic hydrolysis products and related phenolic derivatives

Feeding deterrent activities of ellagic acid, two ellagitannins, gallic acid, pyrogallol, and several gallic acid derivatives towards three species of aphids were determined. The most sensitive species tested was Schizaphis graminum (Rondani), the least sensitive was Acyrthosiphon pisum (Harris). Myzus persicae (Sulzer) was of intermediate sensitivity. Ellagic acid (ED₅₀=15 ppm) and n-decyl gallate (ED₅₀=16 ppm) were particularly potent against S. graminum, while n-octyl gallate was the most active compound tested against A. pisum (ED₅₀=182 ppm) and M. persicae (ED₅₀=56 ppm). The ellagitannins, geraniin and pedunculagin, were active against S. graminum and M. persicae, but not against A. pisum. Methylation of the free hydroxyl groups of gallic acid resulted in a large decrease in activity, while esterification of its carboxyl group with alkyl chains of increasing length resulted in increasing activity against S. graminum. Against A. pisum and M. persicae, ellagic acid, gallic acid and 3,4,5-trimethoxybenzoic acid were inactive, whereas pyrogallol and the gallate esters were at least moderately active as feeding deterrents.

---

Résumé L'examen a porté sur l'action répulsive, lors de l'alimentation de trois espèces de pucerons, de l'acide ellgique, de deux ellagitanins, de l'acide gallique, du pyrogallol et de plusieurs dérivés de l'acide gallique. Schizaphis graminum Rondani a été l'espèce la plus sensible, tandis que Acyrthosiphon pisum. Harris a été la moins sensible; la sensibilité de Myzus persicae Sulzer était intermédiaire. L'acide ellagic (ED₅₀=15 ppm) et le n-décyl gallate (ED₅₀=16 ppm) ont été particulièrement actifs contre S. graminum, tandis que le n-octyl gallate a été le produit le plus actif contre A. pisum (ED₅₀=182 ppm) et M. persicae (ED₅₀=56 ppm). Les ellagitanins, géraniine et pédunculagine ont été actifs contre S. graminum et M. persicae, mais pas contre A. pisum. La méthylation des groupes hydroxyl libres de l'acide gallique a réduit fortement l'activité, tandis qu l'estérification de son groupe carboxyl avec des chaînes alkyl de longuers croissantes a augmenté l'activité contre S. graminum. Les acides ellagique, gallique et 3,4,5-triméthoxybenzoïque ont été inactifs contre A. pisum et M. persicae, tandis que le pyrogallol et les esters de gallate on été pour le moins des répulsifs modérément actifs au cours de l'alimentation.

     

Two ellagitannins from the stem bark of Caesalpinia pulcherrima

Two ellagitannins have been isolated from the stem bark of C. pulcherrima. These tannins have been assigned structures with glucose as the carbohydrate core, esterified with two galloyl and one hexahydroxydiphenoyl group and with a galloyl, a hexahydroxydiphenoyl and a m-digalloyl group, respectively.     

A systematic study of the polyphenolic composition of aqueous extracts deriving from several Cistus genus species: evolutionary relationship

Introduction – Cistaceae is a large family of shrubs widely spread over the Mediterranean area. It includes Helianthemum, Halimium and Cistus genus. Cistus genus contains approximately 20 species distributed in three subgenus. The essential oil of Cistus species has been thoroughly studied, but the polyphenolic composition of the aerial parts of the different Cistus species needs further characterisation. Objective – To perform a comparative analysis of the qualitative and quantitative polyphenolic composition of the aerial parts of the most commonly distributed Spanish Cistus species in order to find a relationship between chemotype and subgenus. Methodology – Thirteen aqueous extracts derived from 10 different Cistus species were analysed by using HPLC with diode array‐detection coupled to electrospray ion trap mass spectrometry technique (HPLC‐DAD‐ESI‐MS/MS). Their major compounds were identified and ellagitannins were quantified. Principal component analysis (PCA) was performed on the most relevant compounds to find out the statistical association between chemotype and variety. Results – Three main groups of compounds were found, i.e. ellagitannins, flavonoids and phenolic acids derivatives. The polyphenolic profile was specific for each species, although the abundance of some compounds also varied depending on the soil type. Whereas C. ladanifer, C. salviifolius, C. populifolius and C. libanotis were specially rich in ellagitannins, C. clusii, C. laurifolius and C. monspeliensis contained significant amounts of flavonoids and much less ellagitannins. In contrast, C. crispus, C. incanus and C. albidus showed a polyphenolic profile mostly based on flavonoids. PCA analysis showed a strong relationship between Cistus subgenus and its chemotype based on the most relevant water‐soluble polyphenolic compounds. Conclusions – Chemical composition of the leaves' aqueous extracts from plants belonging to the Cistus genus is strongly related to their subgenus, in agreement to previous taxonomical and phylogenetic divisions. In contrast, soil and climate are less influencing factors. Leucocistus and Halimioides subgenus showed a higher content in ellagitannins. However, Cistus subgenus had higher flavonoid content. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimization of Ellagitannase Production by Aspergillus niger GH1 by Solid-State Fermentation

Ellagic acid is one of the most bioactive antioxidants with important applications in pharmaceutical, cosmetic, and food industries. However, there are few biotechnological processes developed for its production, because it requires precursors (ellagitannins) and the corresponding biocatalyst (ellagitannase). The aim of this study was to optimize the culture conditions for ellagitannase production by Aspergillus niger in solid-state fermentation (SSF). The bioprocess was carried out into a column bioreactor packed with polyurethane foam impregnated with an ellagitannins solution as carbon source. Four strains of Aspergillus niger (PSH, GH1, HT4, and HC2) were evaluated for ellagitannase production. The study was performed in two experimental steps. A Plackett–Burman design was used to determine the influencing parameters on ellagitannase production. Ellagitannins concentration, KCl, and MgSO₄ were determined to be the most significant parameters. Box–Behnken design was used to define the interaction of the selected parameters. The highest enzyme value was obtained by A. niger PSH at concentrations of 7.5 g/L ellagitannins, 3.04 g/L KCl, and 0.76 g/L MgSO₄. The methodology followed here allowed increasing the ellagitannase activity 10 times over other researcher results (938.8 U/g ellagitannins). These results are significantly higher than those reported previously and represent an important contribution for the establishment of a new bioprocess for ellagic acid and ellagitannase production.