Peptide transporters are integral plasma membrane proteins that mediate the cellular uptake of dipeptides and tripeptides in addition to a variety of peptidomimetics. The carriers, which occur predominantly in the brush-border membranes of epithelial cells of the small intestine, lung, choroid plexus and kidney, contribute to absorption, distribution and elimination of their substrates. The cellular uptake of peptides and peptidomimetics involves the cotransport of protons down an inwardly directed, electrochemical proton gradient that provides the driving force and causes the electrogenicity of the translocation step. Peptide transporters represent excellent targets for the delivery of pharmacologically active compounds because their substrate-binding site can accommodate a wide range of molecules of differing size, hydrophobicity and charge.

Mammalian peptide transporters as targets for drug delivery

Natural products and their derivatives are important sources for drug discovery; however, they usually have poor solubility and low activity and require structural modification. Amino acids are highly soluble in water and have a wide range of activities. The introduction of amino acids into natural products is expected to improve the performance of these products and minimize their adverse effects. Therefore, this review summarizes the application of amino acids in the structural modification of natural products and provides a theoretical basis for the structural modification of natural products in the future. The articles were divided into six types based on the backbone structures of the natural products, and the related applications of amino acids in the structural modification of natural products were discussed in detail.

/pdf/application-of-amino-acids-in-the-structural-modification-of-2np2ig0b9s.pdf

Application of Amino Acids in the Structural Modification of Natural Products: A Review

Design, synthesis and evaluation of novel scutellarin and scutellarein-N,N-bis-substituted carbamate-l-amino acid derivatives as potential multifunctional therapeutics for Alzheimer's disease.

A valine carbamate prodrug of daidzein was synthesized to improve its bioavailability because of the poor solubility and low permeability of daidzein. To evaluate the pharmacokinetic behavior of the prodrug, a sensitive and high-throughput method was developed and validated for the simultaneous determination of daidzein and its prodrug in rat plasma. The samples were extracted by ethyl acetate and then analyzed by a supercritical fluid chromatography with electrospray ionization tandem mass spectrometry method. The separation was achieved by an ACQUITY UPC2 ™ BEH 2-EP column maintained at 40°C using carbon dioxide (≥99.99%) and methanol within 3.0 min by gradient elution. The mass transition ion pairs were m/z 254.8→136.7, 398.0→254.9, and 271.0→91.07 for daidzein, the prodrug, and genistein, respectively. The calibration curves were linear over the concentration ranges of 2-500 (r > 0.997) and 10.0-5000.0 ng/mL (r > 0.996) with lower limits of quantification of 2 and 10 ng/mL for daidzein and the prodrug, respectively. The intra- and interday accuracy and precision were within ±15% for all quality control samples. This developed method enabled high specificity, low cost, low solvent consumption, and a brief analysis time and was successfully applied to a bioavailability evaluation of daidzein and its carbamate prodrug.

A sensitive, high-throughput, and eco-friendly analysis of daidzein and its valine carbamate prodrug in rat plasma by supercritical fluid chromatography with tandem mass spectrometry

In this article, a DPPH·-luminol chemiluminescence (CL) system was reported and the CL mechanism was discussed according to the CL kinetic properties after sequence injecting DPPH· into the DPPH·-luminol reaction mixture. It was observed that scutellarin could inhibit the CL response of the DPPH·-luminol system. Based on this observation, a simple and rapid flow injection CL method was developed for the determination of scutellarin using the inhibition effect in alkaline medium. The optimized chemical conditions for the CL reaction were 5 × 10-6  mol/L DPPH· and 1.0 × 10-4  mol/L luminol in 0.01 mol/L NaOH. Under optimized conditions, the CL intensity was inversely proportional to the concentration of scutellarin over the ranges 5-2000 and 40-3200 ng/ml in pharmaceutical injection and rat plasma, respectively. The limits of detection (S/N = 3) were 5 and 40 ng/ml in preparations and rat plasma, respectively. Furthermore, the precision, recovery and stability of the validated method were acceptable for the determination of scutellarin in both pharmaceutical injections and rat plasma. The presented method was successfully applied in the determination of scutellarin in pharmaceutical injections and real rat plasma samples.

DPPH·–luminol chemiluminescence system and its application in the determination of scutellarin in pharmaceutical injections and rat plasma with flow injection analysis

A series of 4′-l-amino acid carbamate derivatives of scutellarin methyl ester were synthesized Physiochemical properties evaluation results showed that designed target compounds have higher chemical and enzymatic stability, and aqueous solubility The permeability (P
 app
 AP to BL) of 4c, 4f, and 4g in Caco-2 cell was 8, 7, and 13 times higher than that of scutellarin, respectively, especially 4g had highest P
 app AP to BL value (185 ± 029 × 10−6 cm/s) and lowest ER (P
 app BL to AP/P
 app
 AP to BL) value 056 In vitro anti-oxidative evaluation results revealed that 4g can protect against H2O2-induced PC12 cells oxidative damage by attenuating the MMP loss and decreasing H2O2-induced ROS production

l-Amino acid carbamate prodrugs of scutellarin: synthesis, physiochemical property, Caco-2 cell permeability, and in vitro anti-oxidative activity

The invention discloses flavonoid compounds which can treat neurodegenerative disease and have the structures represented by the following structure general formula I, II and III, and preparation methods and an application thereof. Physicochemical properties and in-vitro metabolism experiments prove that the compounds have better physicochemical and metabolic properties compared with scutellarin and seutellarein, and can be applied in preparation of drugs for treating the neurodegenerative disease.

Carbamate derivates of scutellarin and seutellarein, and application thereof

The invention discloses a compound with a chemical structure as described in the specification, and pharmaceutically acceptable salts, salt crystalline hydrates and salt crystalline solvents thereof. In the chemical structure, R1 is H or OH; R2 is H or OH; and R3 is an alkyl group with 1 to 4 carbon atoms. Antiviral activity and primary hepatocyte uptaking experiment results show that the compound has better antiviral activity and liver cell transfer specificity than adefovir dipivoxil, and can be used for preparation of drugs treating hepatitis B virus infection.

Adefovir thio L-amino acid ester and mono bile acid ester derivatives and preparation method thereof

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l-Amino acid carbamate prodrugs of scutellarin: synthesis, physiochemical property, Caco-2 cell permeability, and in vitro anti-oxidative activity

Carbamate derivates of scutellarin and seutellarein, and application thereof

Adefovir thio L-amino acid ester and mono bile acid ester derivatives and preparation method thereof