Enhanced water solubility, antioxidant activity, and oral absorption of hesperetin by D-α-tocopheryl polyethylene glycol 1000 succinate and phosphatidylcholine / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Hesperetin, an abundant bioactive component of citrus fruits, is poorly water-soluble, resulting in low oral bioavailability. We developed new formulations to improve the water solubility, antioxidant activity, and oral absorption of hesperetin. Two nano-based formulations were developed, namely hesperetin-TPGS (D-α-tocopheryl polyethylene glycol 1000 succinate) micelles and hesperetin-phosphatidylcholine (PC) complexes. These two formulations were prepared by a simple technique called solvent dispersion, using US Food and Drug Administration (FDA)-approved excipients for drugs. Differential scanning calorimetry (DSC) and dynamic light scattering (DLS) were used to characterize the formulations' physical properties. Cytotoxicity analysis, cellular antioxidant activity assay, and a pharmacokinetic study were performed to evaluate the biological properties of these two formulations. The final weight ratios of both hesperetin to TPGS and hesperetin to PC were 1:12 based on their water solubility, which increased to 21.5- and 20.7-fold, respectively. The hesperetin-TPGS micelles had a small particle size of 26.19 nm, whereas the hesperetin-PC complexes exhibited a larger particle size of 219.15 nm. In addition, the cellular antioxidant activity assay indicated that both hesperetin-TPGS micelles and hesperetin-PC complexes increased the antioxidant activity of hesperetin to 4.2- and 3.9-fold, respectively. Importantly, the in vivo oral absorption study on rats indicated that the micelles and complexes significantly increased the peak plasma concentration (Cmax) from 2.64 μg/mL to 20.67 and 33.09 μg/mL and also increased the area under the concentration-time curve of hesperetin after oral administration to 16.2- and 18.0-fold, respectively. The micelles and complexes increased the solubility and remarkably improved the in vitro antioxidant activity and in vivo oral absorption of hesperetin, indicating these formulations' potential applications in drugs and healthcare products.

PEG-induced fusion of phosphatidylcholine-liposomes with protoplasts and post-fusion evaluation of plating efficiency and enrichment in plasmamembrane phosphatidylcholine of protoplasts in Datura innoxia Mill.

Liposomes entrapping fluorescein diacetate were fused with protoplasts of Datura innoxia Mill by employing polyethylene glycol (PEG) as the fusogen. Factors that influence liposome-protoplast fusion were optimized as a function of PEG-concentration and incubation duration, liposome composition and surface charge and liposome:protoplast ratio. Phosphatidylcholine-liposomes were found ideal for the objectives of the study. Fusion index based on per cent fluorescing protoplasts varied among the protoplast types. PEG-incubation duration in the fusion assay and growth ability of protoplasts to form microcalli subsequent to liposome-protoplast fusion was determined based on protoplast plating-efficiency. Plating efficiency of post-fusion protoplasts increased due to incorporation of liposome-phosphatidylcholine in the plasmamembrane of protoplasts. Results are discussed in relation to the application of liposome-protoplast fusion system in selective modification of plasmamembrane phospholipids of protoplasts.

Insight into the environment of tryptophan in a hydrophobic model peptide upon aggregation and interaction with lipid vesicles: a steady state and time resolved fluorescence study.

Fluorescence spectroscopy is extensively used to monitor binding of peptides to lipid vesicles as well as orientation in the lipid bilayer. In steady-state fluorescence, the emission characteristics of intrinsic and extrinsic fluorophores, which are sensitive to environment are monitored. Life time measurements should yield useful information about the location and flexibility of fluorophores, as these factors have a significant effect on the life times. However, studies on protein structure and dynamics indicate that interpretation of life-time data is complicated (Beechem. J.M. and Brand, L. (1985) Annu. Rev. Biochem. 54, 43-71). Hence, simple well-defined systems should help in interpretation of life time data, especially in lipid-peptide interactions. In order to examine how fluorescence characteristics of tryptophan and anthroyl group would reflect molecular details of peptide aggregation and lipid-peptide interaction, studies have been carried out on a model hydrophobic peptide and its fatty acylated derivative. Steady-state fluorescence measurements suggest that: (1) the fatty acyl chain attached to an amino acid associates with the peptide chain in aqueous environment. (2) In the lipid bilayer, the acyl chain is oriented perpendicular to the lipid bilayer surface with the peptide chain at an angle to it. Analysis of the fluorescence decay of tryptophan indicates the predominance of a very short life-time component (<1ns) in aqueous environment and lipid-vesicles. Since the preexponentials were not negative, it is unlikely that this is due to extensive deactivation process. We attribute the observation of the low life time component to predominance of one rotamer around (C alpha-C beta)bond of tryptophan in aqueous and lipid environments. Our investigations suggest that fluorescence life time data need to be complemented with steady state measurements to get an insight into details of lipid-peptide interaction.

Lipid molecular shapes and membrane architecture.

A simple biomembrane like erythrocyte contains well over hundred lipid species with diverse molecular shapes differing in the number of acyl chains, chain length, unsaturation and head group composition. A delicate balance between these molecular shapes is necessary in order to have a functional membrane. It is well established that the activities of a number of membrane-bound enzymes and other properties such as aggregation, spontaneous vesiculation, pathophysiological properties and lipid-protein interactions of lipids depend on the acyl chain length, unsaturation and head group composition. In fact, the molecular shape of a phospholipid molecule, as modulated by changes in chain length, unsaturation and head group composition, is probably what is affecting the above mentioned properties. The molecular shape of a lipid depends on a dimensionless packing parameter, S, the value of which influences the size and shape of aggregate formed upon hydration. In fact, the additivity of S values of lipid mixtures explains a number of experimental observations. The molecular shape concept, although very simple, explains many membrane phenomena like complementarity of molecular shapes of non-bilayer lipids to form stable bilayers. Membrane permeability is controlled to a large extent by lipid packing which depends upon molecular shapes. In fact, membranes maintain their lamellar structure by delicately balancing the composition of bilayer-forming and non-bilayer-forming lipids indicating that complementarity of molecular shapes is essential to maintain the permeability barrier. Based on this, the complementary molecular shape model of cell membrane is proposed.

Fatty acid composition and dynamics of phospholipids from fresh water fish Prochilodus Lineatus brain and spinal cord

Se estudió la composición de fosfolípidos y ácidos grasos de lípidos de cerebro y médula del pez de de agua dulce Prochilodus lineatus (sábalo). También hemos investigado la anisotropía de fluorescencia de fosfolípidos marcados con 1.6-difenil-1.3.5 hexatrieno. Se halló que la fosfatidilcolina era el fosfolípido más abundante, seguido por la fosfatidil etanolamina, fosfatidil-serina, fosfatidil-inositol y la esfingomielina. La composición de ácidos grasos de todos los fosfolípidos, exceptuando la esfingomielina, mostró la presencia de ácidos no saturados de la series n-3, n-6 y n-9. El ácido araquidónico evidenció la presencia de ácidos grasos polinosaturados de la serie n-6, y se lo encontró preferentemente en el fosfatidil-inositol. Los ácidos grasos n-3 fueron representados por los ícidos 20:5n-3, (araquidónico) y 3 en peces de agua dulce contrasta con la ausencia de los n-6 en el tejido nervioso de peces marinos. La fosfatidilcolina mostró la mayor fluidez de todos los fosfolípidos de cerebro y médula

Liquid membrane phenomenon in the actions of digitalis.

The liquid membrane phenomenon in the actions of digitalis glycosides (digitoxin, digoxin and ouabain) has been studied. Formation of liquid membranes, in series with a supporting membrane, by digitalis alone and by digitalis in association with lecithin and cholesterol has been demonstrated. The results obtained on the transport of relevant permeants, viz. sodium, potassium and calcium ions and dopamine, adrenaline, noradrenaline and serotonin, in the presence of the liquid membrane generated by digitalis in association with lecithin and cholesterol indicate that the liquid membrane barrier to transport may have a relevance with the biological actions of digitalis.