Direct quantification of mono- and di-D-α-tocopherol polyethylene glycol 1000 succinate by high performance liquid chromatography

Rp-HPLC Determination of Quercetin in a Novel D-α-Tocopherol Polyethylene Glycol 1000 Succinate Based SNEDDS Formulation: Pharmacokinetics in Rat Plasma

Despite its proven efficacy in diverse metabolic disorders, quercetin (QU) for clinical use is still limited because of its low bioavailability. D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) is approved as a safe pharmaceutical adjuvant with marked antioxidant and anti-inflammatory activities. In the current study, several QU-loaded self-nanoemulsifying drug delivery systems (SNEDDS) were investigated to improve QU bioavailability. A reversed phase high performance liquid chromatography (RP-HPLC) method was developed, for the first time, as a simple and sensitive technique for pharmacokinetic studies of QU in the presence of TPGS SNEDDS formula in rat plasma. The analyses were performed on a Xterra C₁₈ column (4.6 × 100 mm, 5 µm) and UV detection at 280 nm. The analytes were separated by a gradient system of methanol and phosphate buffer of pH 3. The developed RP-HPLC method showed low limit of detection (LODs) of 7.65 and 22.09 ng/mL and LOQs of 23.19 and 66.96 ng/mL for QU and TPGS, respectively, which allowed their determination in real rat plasma samples. The method was linear over a wide range, (30-10,000) and (100-10,000) ng/mL for QU and TPGS, respectively. The selected SNEDDS formula, containing 50% w/w TPGS, 30% polyethylene glycol 200 (PEG 200), and 20% w/w pumpkin seed oil (PSO), showed a globule size of 320 nm and -28.6 mV zeta potential. Results of the pharmacokinetic studies showed 149.8% improvement in bioavailability of QU in SNEDDS relative to its suspension. The developed HPLC method proved to be simple and sensitive for QU and TPGS simultaneous determination in rat plasma after oral administration of the new SNEDDS formula.

Liquid ToF-SIMS revealing the oil, water, and surfactant interface evolution

Bilge water from ships is regarded as a major pollutant in the marine environment. Bilge water exists in a stable oil-in-water (O/W) emulsion form. However, little is known about the O/W liquid-liquid (l-l) interface. Traditional bulk characterization approaches are not capable of capturing the chemical changes at the O/W l-l interface. Although surfactants are deemed essential in droplet formation, their roles in bilge water stabilization have not been fully revealed. We have utilized novel in situ chemical imaging tools including in situ scanning electron microscopy (SEM) and in situ time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study the evolving O/W interface using a NAVY bilge model for the first time. The droplet size distribution (DSD) does not change significantly without the addition of X-100 surfactants under static or rocking conditions. Both the oil components and the water clusters are shown to evolve over time at the O/W droplet interface by in situ liquid SIMS imaging. Of particular interest to droplet stabilization, the contribution of surfactants to the aged bilge droplets becomes more significant as the droplet size increases. The higher mass surfactant component does not appear on the droplet surface immediately while many lower mass surfactants are solvated inside the droplet. We have provided the first three-dimensional images of the evolving O/W interface and demonstrated that in situ surface chemical mapping is powerful enough to reveal the complex and dynamic l-l interface in the liquid state. Our observational insights suggest that surfactants are important in mediating droplet growth and facilitating effective separation of bilge water emulsion.

Surface evolution of synthetic bilgewater emulsion

Bilgewater is a regulated shipboard produced waste stream that often contains oil-in-water emulsion. Fundamental knowledge of emulsion surface changes is required for improved wastewater treatment; however, limited information is currently available. We have reported the first surface characterization of synthetic bilgewater emulsions using time-of-flight secondary ion mass spectrometry (ToF-SIMS) coupled with optical microscopy. A Navy standard bilgewater solution consisting of a hydrocarbon and detergent mixture is used as the synthetic bilgewater emulsion model. Both fresh and aged emulsion samples are analyzed to determine their droplet size distributions (DSDs) and surface chemical composition. Our results show that fresh emulsions are largely mono-modal with hydrocarbon fragments as the main surface composition. Aged emulsions are also mono-modal with slightly larger size. Both SIMS spectral comparison and Principal Component Analysis (PCA) show that some surfactant components appear on the fresh emulsion surface while larger molecular weight components appear at the aged bilge droplet surface. Our results indicate that the oil-water interface evolves after emulsion droplet formation. More importantly, surface evolution not only changes the bilgewater DSD, but also alters the surface chemical composition and reactivity.

Synthesis, characterization, and in-vitro antitumor activity of the polyethylene glycol (350 and 1000) succinate derivatives of the tocopherol and tocotrienol isomers of Vitamin E

Vitamin E refers to a group of saturated tocopherol (T) isomers and the biologically more active unsaturated tocotrienol (T₃) isomers. PEGylated α-tocopherol, commercially known as Vitamin E TPGS, has been used as an emulsifier and therapeutic agent for children with vitamin E deficiency. Limited information, however, is available about the PEG conjugates of the tocotrienol isomers of vitamin E. The current work was therefore undertaken to synthesize and characterize the water soluble polyethylene glycol (PEG 350 and 1000) derivatives of T and T₃. Yield and the identity of the synthesized products were confirmed by ¹H NMR, mass spectroscopy, HPLC, and thermal analysis. The self-assembly of the PEGylated vitamin E isomers in water at critical micelle concentrations (CMC) was further confirmed by size, zeta, and Cryo-TEM image analysis. While stable at pH 7.4, PEG conjugates were found to rapidly hydrolyze at pH 1.2. Our data showed that PEGylated T₃ isomers were significantly more active as inhibitors for P-glycoprotein than PEGylated T. The in vitro cytotoxicity of the conjugates was also tested against a large panel of normal and tumorigenic cells. Of the conjugates, γ-T₃PGS 1000 and δ-T₃PGS 1000 were found to have the least toxicity against non-tumorigenic breast and pancreatic cell lines, which may be advantageous for its use as functional excipients in drug delivery. The results from the current work have demonstrated the feasibility of synthesizing PEGylated conjugates of vitamin E isomers and highlighted the potential use of these conjugates in drug delivery as functional and safer excipients especially for γ-T₃PGS 1000 and δ-T₃PGS 1000 conjugate.

PEGylated γ-tocotrienol isomer of vitamin E: Synthesis, characterization, in vitro cytotoxicity, and oral bioavailability

Vitamin E refers to a family of eight isomers divided into two subgroups, tocopherols and the therapeutically active tocotrienols (T3). The PEGylated α-tocopherol isomer of vitamin E (vitamin E TPGS) has been extensively investigated for its solubilizing capacity as a nonionic surfactant in various drug delivery systems. Limited information, however, is available about the PEG conjugates of the tocotrienol isomers of vitamin E. In this study two PEGylated γ-T3 variants with mPEG molecular weights of 350 (γ-T3PGS 350) and 1000 (γ-T3PGS 1000) were synthesized by a two-step reaction procedure and characterized by (1)H NMR, HPLC, and mass spectroscopy. The physical properties of their self-assemblies in water were characterized by zeta, CMC, and size analysis. Similar physical properties were found between the PEGylated T3 and vitamin E TPGS. PEGylated T3 were also found to retain the in vitro cytotoxic activity of the free T3 against the MCF-7 and the triple-negative MDA-MB-231 breast cancer cells. PEGylated γ-T3 also increased the oral bioavailability of γ-T3 by threefolds when compared to the bioavailability of γ-T3 formulated into a self-emulsified drug delivery system. No significant differences in biological activity were found between the PEG 350 and 100 conjugates. Results from this study suggest that PEGylation of γ-T3 represents a viable platform for the oral and parenteral delivery of γ-T3 for potential use in the prevention of breast cancer.

TPGS emulsified zein nanoparticles enhanced oral bioavailability of daidzin: in vitro characteristics and in vivo performance

A novel drug delivery system, TPGS 1000 (TPGS) emulsified zein nanoparticles (TZN), were designed with an objective to improve the oral bioavailability of daidzin, an isoflavone glycoside with estrogenic activities. Zein nanoparticles (ZN) and TZN were fabricated using an antisolvent method. They were found to be spherical in shape with a mean size around 200 nm and a low polydispersity. Their zeta potentials were about +25 mV at pH 5.5 and -23 mV at pH 7.4. Adding TPGS as an emulsifier increased the encapsulation efficiency of daidzin in ZN from 53% to 63%. Daidzin loaded TZN had a slower daidzin release compared with daidzin loaded ZN in both simulated digestive fluids and a pH 7.4 buffer. Confocal laser scanning microscopy suggested that the cellular uptake of coumarin-6 labeled TZN in human intestinal epithelial Caco-2 cells were significantly higher than fluorescent ZN. Cellular uptake and transport studies revealed that daidzin in TZN were taken up more efficiently into Caco-2 cells and transported more quickly through Caco-2 monolayer than daidzin solution. A pharmacokinetic study demonstrated that the Cmax of daidzein in mice after oral administration of daidzin loaded TZN was 5.66 ± 0.16 μM, which was improved by 2.64-fold compared with that of daidzin solution (2.14 ± 0.04 μM). Moreover, the areas under the curve (AUC0-12 h) for daidzin loaded in TZN were enhanced by 2.4-fold compared with that of daidzin solution. These results suggested that TZN could be an effective strategy to improve the oral bioavailability of isoflavone glycosides like daidzin.

Sequential determination of fat- and water-soluble vitamins in green leafy vegetables during storage

The simultaneous analysis of fat- and water-soluble vitamins from foods is a difficult task considering the wide range of chemical structures involved. In this work, a new procedure based on a sequential extraction and analysis of both types of vitamins is presented. The procedure couples several simple extraction steps to LC-MS/MS and LC-DAD in order to quantify the free vitamins contents in fresh-cut vegetables before and after a 10-days storage period. The developed method allows the correct quantification of vitamins C, B(1), B(2), B(3), B(5), B(6), B(9), E and provitamin A in ready-to-eat green leafy vegetable products including green lettuce, ruby red lettuce, watercress, swiss chard, lamb's lettuce, spearmint, spinach, wild rocket, pea leaves, mizuna, garden cress and red mustard. Using this optimized methodology, low LOQs were attained for the analyzed vitamins in less than 100 min, including extraction and vitamin analysis using 2 optimized procedures; good repeatability and linearity was achieved for all vitamins studied, while recoveries ranged from 83% to 105%. The most abundant free vitamins found in leafy vegetable products were vitamin C, provitamin A and vitamin E. The richest sample on vitamin C and provitamin A was pea leaves (154 mg/g fresh weight and 14.4 mg/100g fresh weight, respectively), whereas lamb's lettuce was the vegetable with the highest content on vitamin E (3.1 mg/100 g fresh weight). Generally, some losses of vitamins were detected after storage, although the behavior of each vitamin varied strongly among samples.