Phytochemical shift from condensed tannins to flavonoids in transgenic Betula pendula decreases consumption and growth but improves growth efficiency of Epirrita autumnata larvae

Despite active research, antiherbivore activity of specific plant phenolics remains largely unresolved. We constructed silver birch (Betula pendula) lines with modified phenolic metabolism to study the effects of foliar flavonoids and condensed tannins on consumption and growth of larvae of a generalist herbivore, the autumnal moth (Epirrita autumnata). We conducted a feeding experiment using birch lines in which expression of dihydroflavonol reductase (DFR), anthocyanidin synthase (ANS) or anthocyanidin reductase (ANR) had been decreased by RNA interference. Modification-specific effects on plant phenolics, nutrients and phenotype, and on larval consumption and growth were analyzed using uni- and multivariate methods. Inhibiting DFR expression increased the concentration of flavonoids at the expense of condensed tannins, and silencing DFR and ANR decreased leaf and plant size. E. autumnata larvae consumed on average 82% less of DFRi plants than of unmodified controls, suggesting that flavonoids or glandular trichomes deter larval feeding. However, larval growth efficiency was highest on low-tannin DFRi plants, indicating that condensed tannins (or their monomers) are physiologically more harmful than non-tannin flavonoids for E. autumnata larvae. Our results show that genetic manipulation of the flavonoid pathway in plants can effectively be used to produce altered phenolic profiles required for elucidating the roles of low-molecular weight phenolics and condensed tannins in plant–herbivore relationships, and suggest that phenolic secondary metabolites participate in regulation of plant growth.</p

Retention of Tannin-C is Associated with Decreased Soluble Nitrogen and Increased Cation Exchange Capacity in a Broad Range of Soils

Phenolic compounds, called tannins, can be retained by soil and affect soluble N but have been studied in only a few soil types. Surface samples (0–10 cm), collected from the United States and Canada, were treated with water (Control) or solutions containing procyanidin, catechin, ß-1,2,3,4,6-pentagalloyl-O-Dglucose (PGG), tannic acid, gallic acid, or methyl gallate. Soluble C and N in treatment supernatants and after incubation (16 h, 80°C) were measured to determine retention of treatment C and effects on soluble N and cation exchange capacity (CEC). Retention varied significantly with treatment (T) and soil order (S) and was greatest for PGG \u3e tannic acid \u3e procyanidin \u3e catechin \u3e methyl gallate \u3e gallic acid and in Alfisols, Aridisols and Mollisols compared Ultisols. However, differences among soil orders were observed only for strongly retained compounds (T × S, P \u3c 0.001). Extraction of soluble N was decreased by gallic acid and tannins, especially PGG, but unaffected by methyl gallate or catechin. All treatments decreased soluble N from Aridisols while Entisols were less affected by tannins (T × S, P \u3c 0.01). Soil CEC was significantly increased by tannins but unaffected by other compounds. However, CEC increased more in Aridisols than in Mollisols or Ultisols and treatment effects were small and unvarying in Ultisols (T × S, P \u3c 0.001). Changes to both soluble N and CEC were linearly related with retention of treatment C. Tannins produced effects associated with improved soil quality on a broad range of soils and may have a role in land management

Conformation and Aggregation of Human Serum Albumin in the Presence of Green Tea Polyphenol (EGCg) and/or Palmitic Acid

Polyphenols such as epigallocatechin gallate (EGCg) may have roles in preventing some chronic diseases when they are ingested as components of plant-based foods and beverages. Human serum albumin (HSA) is a multi-domain protein that binds various ligands and aids in their transport, distribution, and metabolism in the circulatory system. In the present study, the HSA-EGCg interaction in the absence or presence of fatty acid has been investigated. F&ouml;rster resonance energy transfer (FRET) was used to determine inter- and intra-domain distances in the protein with and without EGCg and palmitic acid (PA). By labeling Cys-34 with 7-(diethyl amino)-4-methylcoumarin 3-maleimide (CPM), the distance between Trp-214 at domain IIA and CPM-Cys-34 at domain IA could be established. A small amount of PA decreased the distance, while a large amount increased the distance up to 5.4 &Aring;. EGCg increased the inter-domain distance in HSA and HSA-PA up to 2.8 and 7.6 &Aring;, respectively. We concluded that PA affects protein conformation more significantly compared to EGCg. Circular dichroism (CD) established that EGCg affects protein secondary structure more significantly than PA. PA had little effect on the &alpha;-helix content of HSA, while EGCg decreased the &alpha;-helix content in a dose-dependent fashion. Moreover, EGCg decreased &alpha;-helix content in HSA and HSA-PA to the same level. Dynamic light scattering (DLS) data revealed that both PA and EGCg increased HSA aggregation. EGCg increased HSA aggregation more significantly and promoted formation of aggregates that were more heterogenous. Any of these effects could impact the ability of serum albumin to transport and stabilize ligands including EGCg and other polyphenols

Role of the Flavan-3-ol and Galloyl Moieties in the Interaction of (−)-Epigallocatechin Gallate with Serum Albumin

The principal green tea polyphenol, (−)-epigallocatechin-3-<i>O</i>-gallate (EGCg), may provide chemoprotection against conditions ranging from cardiovascular disease to cancer. Binding to plasma proteins stabilizes EGCg during its transport to targeted tissues. This study explored the details EGCg binding to bovine serum albumin. Both fluorescence lifetime and intensity data showed that the hydrophobic pocket between subdomains IIA and IIIA is the binding site for EGCg. Fluorescence and circular dichroism were used to establish the roles of the flavan-3-ol and galloyl moieties of the EGCg in binding and to demonstrate a binding-dependent conformational change in the protein. Competitive binding experiments confirmed the location of binding, and molecular modeling identified protein residues that play key roles in the interaction. This model of EGCg–BSA interactions improves the understanding of the likely physiological fate of this green tea-derived bioactive polyphenol