A novel strategy by combining foam fractionation with high-speed countercurrent chromatography for the rapid and efficient isolation of antioxidants and cytostatics from Camellia oleifera cake.

Camellia oleifera cake is a by-product, which is rich in functional chemical components. However, it is typically used as animal feed with no commercial value. The purpose of this study was to isolate and identify compounds from Camellia oleifera cake using a combination of foam fractionation and high-speed countercurrent chromatography (HSCCC) and to investigate their biological activities. Foam fractionation with enhanced drainage through a hollow regular decahedron (HRD) was first established for simultaneously enriching flavonoid glycosides and saponins for further separation of target compounds. Under suitable operating conditions, the introduction of HRD resulted in a threefold increase in enrichment ratio with no negative effect on recovery. A novel elution-extrusion countercurrent chromatography (EECCC) coupled with the consecutive injection mode was established for the successful simultaneous isolation of flavonoid glycosides and saponins. As a result, 38.7 mg of kaemferol-3-O-[2-O-D-glucopyranosyl-6-O-α-L-rhamnopyranosyl]-ß-D-glucopyranoside (purity of 98.17%, FI), 70.8 mg of kaemferol-3-O-[2-O-ß-D-xylopyranosyl-6-O-α-L-rhamnopyranosyl]-ß-D-glucopyranoside (purity of 97.52%, FII), and 560 mg of an oleanane-type saponin (purity of 92.32%, FIII) were separated from the sample (900 mg). The present study clearly showed that FI and II were natural antioxidants (IC50 < 35 µg/mL) without hemolytic effect. FIII displayed the effect of inhibiting Hela cell proliferation (IC50 < 30 µg/mL). Further erythrocyte experiments showed that this correlated with the extremely strong hemolytic effect of FIII. Overall, this study offers a potential strategy for efficient and green isolation of natural products, and is beneficial to further expanding the application of by-products (Camellia oleifera cake) in food, cosmetics, and pharmacy.

Design of diversified self-assembly systems based on a natural rosin-based tertiary amine for doxorubicin delivery and excellent emulsification.

A novel rosin-based ester tertiary amine (RETA) with three hydrophilic groups and a rigid hydrophobic group was synthesized from rosin by Diels-Alder addition, acylation and esterification reactions. RETA was characterized by infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance spectroscopy (13C NMR). Results from testing surface tension, zeta potential, and transmission electron spectroscopy showed that RETA had unique pH responsiveness. RETA self-assembled into worm-like micelles, spherical micelles 130 nm in diameter and big spherical worm-like aggregates with diameter of 2 µm at pH = 5.76, 8.04 and 9.38, respectively. The critical micelle concentration (CMC) of RETA was 0.42 mmol/L, and the surface tension at CMC (γcmc) was 38.73 mN/m when pH was 8.04. The RETA had a potential application in delivering doxorubicin hydrochloride (DOX) due to the pH responsiveness. Self-assembly mixed systems of RETA and rosin-based phosphoric acid (DDPD) were designed to improve emulsification. The mixed systems had obvious synergistic effects and unexpected emulsification. The γcmc and CMC of mixtures were 41.74 mN/m and 0.20 mmol/L, the size of mixture micelles increased up to 300 nm in the optimum molar ratio of RETA/DDPD (7:3) by TEM and cryo-TEM. It was worth noting that the mixture system formed vesicles in the RETA/DDPD molar ratio of 5:5. The stability time of emulsion with RETA and DDPD as emulsifier were only 63 s and 52 s respectively, but the stability time increased to 234 s in the optimum molar ratio. In addition, the formation mechanisms of micelles at different pH and in various mixtures were discussed in detail. What's more, cytotoxicity results showed that the toxicity of RETA was lower significantly than that of lecithin, a food ingredient in egg yolk and soybean. The cell viability was more than 83% in the high concentration of RETA (4000 µg/ml).

Mechanical and viscoelastic properties of cellulose nanocrystals reinforced poly(ethylene glycol) nanocomposite hydrogels.

The preparation and mechanical properties of elastomeric nanocomposite hydrogels consisting of cellulose nanocrystals (CNCs) and poly(ethylene glycol) (PEG) are reported. The aqueous nanocomposite CNC/PEG precursor solutions covalently cross-linked through a one-stage photocross-linking process. The mechanical properties of nanocomposite hydrogels, including Young's modulus (E), fracture stress (σ), and fracture strain (ε), were measured as a function of CNC volume fraction (φCNC, 0.2-1.8%, v/v) within polymeric matrix. It was found that the homogeneously dispersed nanocomposite hydrogels can be prepared with φCNC being less than 1.5%, whereas the heterogeneous nanocomposite hydrogels were obtained with φCNC being higher than 1.5%. The nanocomposite hydrogels exhibited higher strengths and flexibilities when compared with neat PEG hydrogels, where the modulus, fracture stress, and fracture strain enhanced by a factor of 3.48, 5, and 3.28, respectively, over the matrix material alone at 1.2% v/v CNC loading. Oscillatory shear data indicated the CNC-PEG nanocomposite hydrogels were more viscous than the neat PEG hydrogels and were efficient at energy dissipation due to the reversible interactions between CNC and PEG polymer chains. It was proposed that the strong gel viscoelastic behavior and the mechanical reinforcement were related to "filler network", where the temporary interactions between CNC and PEG interfered with the covalent cross-links of PEG.