The small GTP-binding protein rho regulates the assembly of focal adhesions and actin stress fibers in response to growth factors

Antioxidant activity of propolis of various geographic origins

The increased resistance of pathogenic microorganisms is frequently attributed to the extreme and inadequate use of antibiotics and transmission of resistance within and between individuals. To counter the emergence of resistant microorganisms, considerable resources have been invested in the search for new antimicrobials. Plants synthesize a diverse array of secondary metabolites (phytochemicals) known to be involved in defense mechanisms, and in the last few years it is recognized that some of these molecules have health beneficial effects, including antimicrobial properties. In this study, the mechanism of action of gallic (GA) and ferulic (FA) acids, a hydroxybenzoic acid and a hydroxycinnamic acid, was assessed on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Listeria monocytogenes. The targets of antimicrobial action were studied using different bacterial physiological indices: minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), membrane ...

Antibacterial activity and mode of action of ferulic and gallic acids against pathogenic bacteria

Are polyphenols antioxidants or pro-oxidants? What do we learn from cell culture and in vivo studies?

Natural polyphenols are valuable compounds possessing scavenging properties towards radical oxygen species, and complexing properties towards proteins. These abilities make polyphenols interesting for the treatment of various diseases like inflammation or cancer, but also for anti-ageing purposes in cosmetic formulations, or for nutraceutical applications. Unfortunately, these properties are also responsible for a lack in long-term stability, making these natural compounds very sensitive to light and heat. Moreover, polyphenols often present a poor biodisponibility mainly due to low water solubility. Lastly, many of these molecules possess a very astringent and bitter taste, which limits their use in food or in oral medications. To circumvent these drawbacks, delivery systems have been developed, and among them, encapsulation would appear to be a promising approach. Many encapsulation methods are described in the literature, among which some have been successfully applied to plant polyphenols. In this review, after a general presentation of the large chemical family of plant polyphenols and of their main chemical and biological properties, encapsulation processes applied to polyphenols are classified into physical, physico-chemical, chemical methods, and other connected stabilization methods. After a brief description of each encapsulation process, their applications to polyphenol encapsulation for pharmaceutical, food or cosmetological purposes are presented.

/pdf/encapsulation-of-natural-polyphenolic-compounds-a-review-148qv6x05l.pdf

Encapsulation of Natural Polyphenolic Compounds; a Review

Interaction of tea catechins with lipid bilayers has been investigated with liposome systems. Tea catechins are classified into cis-type and trans-type from the configuration of the two hydrogens at the 2 and 3 positions on the C-ring. The amount of trans-type catechins incorporated into liposomes was less than that of the respective cis-type catechins. Furthermore, the order of the partition coefficients of catechins in an n-octanol/PBS system is the same as that of the amount incorporated into liposomes. These results indicate that in addition to the number of hydroxyl groups on the B-ring and the presence of the galloyl moiety, the stereochemical structure of the C-ring also governs the hydrophobicity and the affinity for lipid bilayers. Trans-type catechins with the galloyl moiety were located on the surface of the lipid bilayer, as well as cis-type catechins with the galloyl moiety, and perturbed the membrane structure. These different stereochemical structures should influence the affinity for lipid bilayers, the alteration of membrane structures, and the difference in the order of the biological activities.

Steric Effects on Interaction of Tea Catechins with Lipid Bilayers

Green tea contains a high concentration of such catechins as (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg) Their biological activities have been evaluated by in vitro experiments using cultured cells or bacteria, but the order of activity of the various catechins differed with the study We have been studying the interaction of tea catechins with lipid bilayers, and clarified that the number of hydroxyl groups on the B-ring, the presence of the galloyl moiety, and the stereochemical structure of each catechin govern their affinity for lipid bilayers We investigated in this present study the effects of various external factors on the affinity of tea catechins for lipid bilayers by using liposomes as model membranes The amount of tea catechins incorporated into the lipid bilayers increased with increasing salt concentration in an aqueous medium and decreased with increasing negative electric charge of the lipid bilayers Furthermore, the amount of EGCg or ECg incorporated into the lipid bilayers increased with increasing EC concentration These results reveal that the salt concentration in an aqueous medium, the electric charge of the membrane, and the presence of other catechins governed the affinity of tea catechins for the lipid bilayers

Effects of External Factors on the Interaction of Tea Catechins with Lipid Bilayers

(+)-Catechin derivatives with different alkyl chain lengths were synthesized from (+)-catechin and various straight chain alkylaldehydes in the presence of methyl mercaptan, and their antibacterial activities against Gram-positive bacteria were evaluated. The antibacterial activity increased markedly with elongation of the alkyl chain lengths of the derivatives and reached a maximum at a chain of four to seven carbons. Subsequently, interaction of the (+)-catechin derivatives with a model membrane using liposome was investigated. The derivatives with a chain of three carbons or more were found to have very strong affinity for the membrane. The injury action of the derivatives against the membrane was examined with liposome in which calcein was enclosed as a fluorescent indicator. The leakage was observed in the derivatives with chain lengths of four carbons or more. Particularly the derivatives with chains longer than five carbons are considered to destroy the liposome membrane judging from the degree of the fluorescent leakage. These results implied that the lipophilicity and disrupting ability of the (+)-catechin derivatives to the liposome membrane participate in their antibacterial activity.

Relationship between antibacterial activity of (+)-catechin derivatives and their interaction with a model membrane.

Eighteen flavonoids including two new compounds, four aromatic carboxylic acids, and eleven phenolic acid esters including one new compound were isolated and identified from the ethyl acetate soluble fraction of the 70% ethanol extract of Uruguayan propolis. The new compounds were elucidated as pinobanksin 3-(2-methyl)butyrate (1; recently reported in Usia, T.; Banskota, A. H.; Tezuka, Y.; Midorikawa, K.; Matsushige, K.; Kadota, S. J. Nat. Prod. 2002, 65, 673-676) pinobanksin 3-isobutyrate (2), and 2-methyl-2-butenyl ferulate (24). The constituents isolated from Uruguayan propolis in this study were similar to those of propolis of European and Chinese origin. Thus, it is suggested that the Uruguayan propolis has a plant origin similar to those of propolis from Europe and China.

Studies of the constituents of Uruguayan propolis.

The interaction of a tea catechin, epigallocatechin gallate (EGCg), with the model membrane of dimyristoylphosphatidylcholine (DMPC) was studied by solid-state 31P and 2H NMR. The 31P chemical shift anisotropy of the DMPC phosphate group decreased on addition of EGCg. The 2H NMR spectrum of [4-2H]EGCg, which is deuterated at the 4-position, in the DMPC liposomes gave deuterium nuclei with much smaller quadrupole splittings than those in the solid phase. These 31P and 2H NMR observations provide direct experimental evidence that the EGCg molecule interacts with the lipid bilayers.

https://www.tandfonline.com/doi/pdf/10.1271/bbb.68.1743

Katsuko Kajiya

Papers

Steric Effects on Interaction of Tea Catechins with Lipid Bilayers

Effects of External Factors on the Interaction of Tea Catechins with Lipid Bilayers

Relationship between antibacterial activity of (+)-catechin derivatives and their interaction with a model membrane.

Studies of the constituents of Uruguayan propolis.

Direct evidence of interaction of a green tea polyphenol, epigallocatechin gallate, with lipid bilayers by solid-state Nuclear Magnetic Resonance.