Jinyou Duan

A Novel Chemometric Method for the Prediction of Human Oral Bioavailability

Orally administered drugs must overcome several barriers before reaching their target site. Such barriers depend largely upon specific membrane transport systems and intracellular drug-metabolizing enzymes. For the first time, the P-glycoprotein (P-gp) and cytochrome P450s, the main line of defense by limiting the oral bioavailability (OB) of drugs, were brought into construction of QSAR modeling for human OB based on 805 structurally diverse drug and drug-like molecules. The linear (multiple linear regression: MLR, and partial least squares regression: PLS) and nonlinear (support-vector machine regression: SVR) methods are used to construct the models with their predictivity verified with five-fold cross-validation and independent external tests. The performance of SVR is slightly better than that of MLR and PLS, as indicated by its determination coefficient (R2) of 0.80 and standard error of estimate (SEE) of 0.31 for test sets. For the MLR and PLS, they are relatively weak, showing prediction abilities of 0.60 and 0.64 for the training set with SEE of 0.40 and 0.31, respectively. Our study indicates that the MLR, PLS and SVR-based in silico models have good potential in facilitating the prediction of oral bioavailability and can be applied in future drug design.

Potent Antibacterial Nanoparticles against Biofilm and Intracellular Bacteria

The chronic infections related to biofilm and intracellular bacteria are always hard to be cured because of their inherent resistance to both antimicrobial agents and host defenses. Herein we develop a facile approach to overcome the above conundrum through phosphatidylcholine-decorated Au nanoparticles loaded with gentamicin (GPA NPs). The nanoparticles were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS) and ultraviolet−visible (UV−vis) absorption spectra which demonstrated that GPA NPs with a diameter of approximately 180u2009nm were uniform. The loading manner and release behaviors were also investigated. The generated GPA NPs maintained their antibiotic activities against planktonic bacteria, but more effective to damage established biofilms and inhibited biofilm formation of pathogens including Gram-positive and Gram-negative bacteria. In addition, GPA NPs were observed to be nontoxic to RAW 264.7u2009cells and readily engulfed by the macrophages, which facilitated the killing of intracellular bacteria in infected macrophages. These results suggested GPA NPs might be a promising antibacterial agent for effective treatment of chronic infections due to microbial biofilm and intracellular bacteria.

Chitosan Coupling Makes Microbial Biofilms Susceptible to Antibiotics

Microbial biofilms, prevalent in nature and inherently resistant to both antimicrobial agents and host defenses, can cause serious problems in the chemical, medical and pharmaceutical industries. Herein we demonstrated that conjugation of an aminoglycoside antibiotic (streptomycin) to chitosan could efficiently damage established biofilms and inhibit biofilm formation. This method was suitable to eradiate biofilms formed by Gram-positive organisms, and it appeared that antibiotic contents, molecular size and positive charges of the conjugate were the key to retain this anti-biofilm activity. Mechanistic insight demonstrated chitosan conjugation rendered streptomycin more accessible into biofilms, thereby available to interact with biofilm bacteria. Thus, this work represent an innovative strategy that antibiotic covalently linked to carbohydrate carriers can overcome antibiotic resistance of microbial biofilms, and might provide a comprehensive solution to combat biofilms in industrial and medical settings.

Antioxidative Properties of Crude Polysaccharides from Inonotus obliquus

The mushroom Inonotus obliquus has been widely used as a folk medicine in Russia, Poland and most of the Baltic countries. In this study, water-soluble and alkali-soluble crude polysaccharides (IOW and IOA) were isolated from I. obliquus, and the carbohydrate-rich fractions IOW-1 and IOA-1 were obtained respectively after deproteination and depigmentation. Their contents, such as neutral carbohydrate, uronic acid and protein, were measured. Their antioxidant properties against chemicals-induced reactive species (ROS) including 1,1′-Diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical and superoxide anion radical, as well as their protective effects on H2O2-induced PC12 cell death were investigated. Results showed that I. obliquus polysaccharides can scavenge all ROS tested above in a dose-dependent manner. IOA and its product IOA-1 could rescue PC12 cell viability from 38.6% to 79.8% and 83.0% at a concentration of 20μg/mL. Similarly, IOW and its product IOW-1 at the same dose, can also increase cell viability to 84.9% and 88.6% respectively. The antioxidative activities of water-soluble and alkali-soluble polysaccharide constituents from I. obliquus might contribute to diverse medicinal and nutritional values of this mushroom.

Extraction optimization, characterization and immunity activity of polysaccharides from Fructus Jujubae.

The versatile Fructus Jujubae is widely used in Chinese and Korean traditional medicine. In this study, the extraction optimization, characterization and immunostimulatory activities of polysaccharides from Fructus Jujubae were investigated. Based on a four-variable-three-level Box-Behnken statistical design, the optimal extraction parameters were optimized as follows: extraction temperature 90 °C, extraction time 3.23 h, water to raw material ratio 33:1 and extraction 3 times. Under these conditions, the experimental yield of polysaccharides was 6.47 ± 0.26%, which was close to the predicted yield value (6.54%). The crude Fructus Jujubae polysaccharide was further purified by DEAE-cellulose chromatography repeatedly, and two homogenous fractions, designated as RQP1d and RQP2d with molecular weight of 83.8 and 123.0 kDa respectively, were obtained. Their structures were determined by chemical analysis, Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Finally, preliminary immunological tests indicated that both RQP1d and RQP2d significantly stimulated NO production in RAW264.7 macrophages, and promoted LPS-induced splenocyte proliferation. These data implied Fructus Jujubae polysaccharides had the potential to be explored as novel natural immunostimulant for using in functional foods or medicine.

Characterization of polysaccharides with antioxidant and immunological activities from Rhizoma Acori Tatarinowii

Rhizoma Acori Tatarinowii is widely used in traditional Chinese medicine. In this study, three novel polysaccharides designated RATPW, RATPS1 and RATPS2 were isolated from Rhizoma Acori Tatarinowii by DEAE-52 cellulose chromatography. Their structures were characterized using physicochemical and spectral methods. Chemical analysis indicated that RATPW (6.5×10(3)Da) mainly composed of glucose and fructose. RATPS1 (1.5×10(5)Da) contained galactose and arabinose, while RATPS2 (5.3×10(4)Da) contained ∼49.5% galacturonic acid along with rhamnose, fructose, galactose, and arabinose. In vitro, RATPS2 showed the most significant scavenging activity on DPPH and hydroxyl radical. Three polysaccharides could protect the PC12 cells from H2O2-induced damage. Immunological tests indicated that both RATPW and RATPS2 significantly stimulated NO production and phagocytic activity in RAW264.7, and promoted splenocyte proliferation. These data suggested that polysaccharides RATPW and RATPS2 had the potential as novel natural sources of antioxidative and immunopotentiating agents.

Synergy among thymol, eugenol, berberine, cinnamaldehyde and streptomycin against planktonic and biofilm‐associated food‐borne pathogens

Essential oils have been found to exert antibacterial, antifungal, spasmolytic, and antiplasmodial activity and therapeutic effect in cancer treatment. In this study, the antibacterial activities of four main essential oils components (thymol (Thy), eugenol (Eug), berberine (Ber), and cinnamaldehyde (Cin)) were evaluated against two food‐borne pathogens, Listeria monocytogenes and Salmonella Typhimurium, either alone or in combination with streptomycin. Checkerboard assay demonstrated that Thy and Cin elicited a synergistic effect with streptomycin against L. monocytogenes, while a synergy existed between Cin or Eug and streptomycin against Salm. Typhimurium. Further experiments showed that this synergy was sufficient to eradicate biofilms formed by these two bacteria. Thus, our data highlighted that the combinations of specific components from essential oils and streptomycin were useful for the treatment of food‐borne pathogens, which might help prevent the spread of antibiotic resistance through improving antibiotic effectiveness.

Chitosan improves anti-biofilm efficacy of gentamicin through facilitating antibiotic penetration.

Antibiotic overuse is one of the major drivers in the generation of antibiotic resistant “super bugs” that can potentially cause serious effects on health. In this study, we reported that the polycationic polysaccharide, chitosan could improve the efficacy of a given antibiotic (gentamicin) to combat bacterial biofilms, the universal lifestyle of microbes in the world. Short- or long-term treatment with the mixture of chitosan and gentamicin resulted in the dispersal of Listeria monocytogenes (L. monocytogenes) biofilms. In this combination, chitosan with a moderate molecular mass (~13 kDa) and high N-deacetylation degree (~88% DD) elicited an optimal anti-biofilm and bactericidal activity. Mechanistic insights indicated that chitosan facilitated the entry of gentamicin into the architecture of L. monocytogenes biofilms. Finally, we showed that this combination was also effective in the eradication of biofilms built by two other Listeria species, Listeria welshimeri and Listeria innocua. Thus, our findings pointed out that chitosan supplementation might overcome the resistance of Listeria biofilms to gentamicin, which might be helpful in prevention of gentamicin overuse in case of combating Listeria biofilms when this specific antibiotic was recommended.

A decrease in moisture absorption–retention capacity of N-deacetylation of hyaluronic acid

The linear non-sulfated glycosaminoglycan, hyaluronic acid (HA), is widely distributed throughout connective, epithelial and neural tissues etc., and is of great importance in tissue hydration, lubrication and cellular function. Along with the age growth, HA will lose its acetyl groups under action of HA N-deacetylase in vivo. However, the biological consequence of this physiological process remains largely unknown. Herein two highly N-deacetylated HAs, dHA-6 and dHA-10 were generated via the NH2NH2-HIO3 procedure. Their molecular weights were estimated to be 24 and 16xa0kDa by high performance gel-permeation chromatography (HPGPC), and the N-deacetylation degrees were 79.4xa0% and 93xa0% respectively, as determined by 1H nuclear magnetic resonance (NMR). The study on moisture-absorption (Ra) and -retention (Rh) abilities demonstrated that the Ra values of dHAs under conditions of 81xa0% or 43xa0% relative humidity, as well as the Rh values of dHAs under dry condition or 43xa0% relative humidity, were significantly smaller than that of their respective re-N-acetylated products. The decline of moisture-absorption and –retention capacity after HA N-deacetylation were consistent with the appearance of unsolvated amides remained in the N-deacetylated products, as indicated by circular dichroism (CD) spectroscopy. Our findings implied that HA N-deacetylation, in addition to the decrease of HA contents in the elderly persons, might account for manifestations of naturally aged skin, such as laxity, sagging, and wrinkling.

Unveiling the Mode of Action of Two Antibacterial Tanshinone Derivatives

In this study, 2-(N-pyrrolidine-alkyl) tanshinones bearing pyrrolidine groups were synthesized and the antibacterial mechanism was explored. These derivatives selectively elicited antibacterial activity against Gram-positive bacteria. Moreover, their antibacterial activities were time-, concentration-dependent and persistent. It appeared that Fenton-mediated hydroxyl radicals were involved, and the disruption of cell membranes was observed. This study indicates that 2-(N-pyrrolidine-alkyl) tanshinones might be potential candidates as antibacterial agents.