Synthesis and in vitro evaluation of chlorogenic acid amides as potential hypoglycemic agents and their synergistic effect with acarbose.

Type 2 Diabetes mellitus is a chronic disease considered one of the most severe global health emergencies. Chlorogenic acid (1) has been shown to delay intestinal glucose absorption by inhibiting the activity of α-glucosidase (α-Glu) and α-amylase (α-Amy). In the present work, eleven chlorogenic acid amides have been synthesized and evaluated for their antioxidant properties (as DPPH and ORAC) and inhibition activity towards the two enzymes and, with the aim to obtain dual-action antidiabetic agents. The two most promising hypoglycemic compounds, bearing a tertiary amine function on an alkyl chain (8) and a benzothiazole scaffold (11), showed IC50 values lower than that of (1) (45.5 µM α-Glu; 105.2 µM α-Amy). Amides 8 and 11 were by far more potent α-Glu inhibitors than the antidiabetic drug acarbose (IC50 = 268.4 µM) and about twice less active toward α-Amy than acarbose (IC50 = 34.4 µM). Kinetics experiments on amides 8 and 11 indicated these compounds as mixed-type inhibitors of α-Glu with K'i values of 13.3 and 6.3 µM, respectively. The amylase inhibition occurred with a competitive mechanism in the presence of 8 (Ki = 79.7 µM) and with a mixed-type mechanism with 11 (Ki = 19.1 µM; K'i = 93.6 µM). Molecular docking analyses supported these results, highlighting the presence of additional binding sites in both enzymes. Fluorescence experiments confirmed the grater affinity of amides 8 and 11 towards the two enzymes respect to (1). Moreover, a significant enhancement in acarbose efficacy was observed when inhibition assays were performed adding acarbose and amide 11. The above outcomes pinpointed the benzothiazole-based amide 11 as a promising candidate for further studies on type 2 diabetes treatment, both alone or combined with acarbose.

Chitosan coated chlorogenic acid and rutincomposite phospholipid liposomes: Preparation, characterizations, permeability and pharmacokinetic.

In order to research and enhance bioavailability of chlorogenic acid and rutin(CA-R) via the oral route, chitosan coated composite phospholipid liposomes (C-CPLs) were applied to study on preparation, permeability and pharmacokinetic of C-CA-R-CPLs. TheC-CA-R-CPLs were prepared by the method of ethanol injection. The entrapment efficiency (EE), average particle sizes, polymer disperse index (PDI), zeta potential, shape and in vitro drug release were investigated to characterize physicochemical parameters of C-CA-R-CPLs. The penetration properties from C-CA-R-CPLs were studied through Caco-2 cells model and the pharmacokinetics in Sprague-Dawley (SD) rats were evaluated by rat jugular vein intubation tube. The EE of C-CA-R-CPLs of CA and R was 91.3±2.13% and 92.6±2.44%, particle size of C-CA-R-CPLs was 176.7±2.3 nm, PDI was 0.207±0.014 and zeta potential of 12.61±1.33 mV. CA-R-CPLs and C-CA-R-CPLs were spherical or elliptical sphere and the bilayer of the CPL was observed obviously under transmission electron. The Cmax, t1/2 and AUC0-12 h values of CA and R for groups of C-CA-R-CPLs were significantly increased.In conclusion, TheC-CA-R-CPLs as a novel nano-formulation have potential to be used to enhance the oral bioavailability of poorlywater-soluble drugs after oral administration.

Silica/Polyethylene Glycol Hybrid Materials Prepared by a Sol-Gel Method and Containing Chlorogenic Acid.

Chlorogenic acid (CGA) is a very common dietary polyphenolic compound. CGA is becoming very attractive due to its potential use as preventive and therapeutic agent in many diseases, including cancer. Inorganic/organic hybrid materials are gaining considerable attention in the biomedical field. The sol-gel process provides a useful way to obtain functional organic/inorganic hybrids. The aim of this study was to synthesize silica/polyethylene glycol (PEG) hybrids with different percentages of CGA by sol-gel technique and to investigate their impact on the cancer cell proliferation. Synthesized materials have been chemically characterized through the FTIR spectroscopy and their bioactivity evaluated looking by SEM at their ability to produce a hydroxyapatite layer on their surface upon incubation with simulated body fluid (SBF). Finally, their effects on cell proliferation were studied in cell lines by direct cell number counting, MTT, flow cytometry-based cell-cycle and cell death assays, and immunoblotting experiments. Notably, we found that SiO2/PEG/CGA hybrids exhibit clear antiproliferative effects in different tumor, including breast cancer and osteosarcoma, cell lines in a CGA dependent manner, but not in normal cells. Overall, our results increase the evidence of CGA as a possible anticancer agent and illustrate the potential for clinical applications of sol-gel synthesized SiO2/PEG/CGA materials.

Synthesis, biological evaluation, and metabolic stability of chlorogenic acid derivatives possessing thiazole as potent inhibitors of α-MSH-stimulated melanogenesis.

A series of catechol and dioxolane analogs containing thiazole CGA derivatives have been synthesized and evaluated for their inhibitory activity against α-MSH. The inhibitory activity was improved by replacing an α,ß-unsaturated carbonyl of previously reported caffeamides with thiazole motif. Surprisingly, compound 7d, one of the derivatives of dioxolane analogs, displayed the most potent inhibitory activity with an IC50 of 0.90µM. Further studies on metabolic stability and bioactivation potential were also accomplished.

Synthesis, Anti-HCV, Antioxidant and Reduction of Intracellular Reactive Oxygen Species Generation of a Chlorogenic Acid Analogue with an Amide Bond Replacing the Ester Bond.

Chlorogenic acid is a well known natural product with important bioactivities. It contains an ester bond formed between the COOH of caffeic acid and the 3-OH of quinic acid. We synthesized a chlorogenic acid analogue, 3α-caffeoylquinic acid amide, using caffeic and quinic acids as starting materials. The caffeoylquinc acid amide was found to be much more stable than chlorogenic acid and showed anti-Hepatitis C virus (anti-HCV) activity with a potency similar to chlorogenic acid. The caffeoylquinc acid amide potently protected HepG2 cells against oxidative stress induced by tert-butyl hydroperoxide.

Synthesis and Application of Novel 3D Magnetic Chlorogenic Acid Imprinted Polymers Based on a Graphene-Carbon Nanotube Composite.

A novel three-dimensional (3D) magnetic chlorogenic acid (CGA) imprinted polymer (MMIP) was prepared with novel carbon hybrid nanocomposite as the carrier, chlorogenic acid as the template molecule, and methacrylic acid as the functional monomer. The 3D MMIPs were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, vibrating sample magnetometer, and UV spectrometry in detail. The results showed that the imprinted layer was attached successfully on the surface of a 3D magnetic carbon hybrid nanocomposite. The adsorption performance of the 3D MMIPs was investigated, and the results showed that the 3D MMIPs exhibited high adsorption capacity and fast adsorption rate toward CGA with a maximum adsorption capacity of 10.88 mg g(-1). The extraction conditions involving washing solvent, the pH of eluent solvent, elution volume, and desorption time were also investigated in detail. Combined with high-performance liquid chromatography, the 3D MMIPs have been applied to successfully extract CGA from Eucommia leaf extract samples.

Evaluation of structural and functional properties of chitosan-chlorogenic acid complexes.

The objectives of the present study were to first synthesize chitosan-chlorogenic acid (CA) covalent complex and then compare structural and functional properties between chitosan-CA covalent complex and physical complex. First, chitosan-CA covalent complex was synthesized and its total phenolic content was as high as 276.5 ± 6.2 mg/g. Then structural and functional properties of chitosan-CA covalent and physical complexes were analyzed. The covalent reaction induced formation of both amide and ester bonds in chitosan. Data of X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the complexations of CA changed crystallinity and morphology of chitosan, and covalent complexation induced a larger change of physical structure than physical complexation. In terms of functional properties, chitosan-CA covalent complex exhibited better thermal stability than physical complex in terms of antioxidant activity, and the viscosity of chitosan was significantly increased by covalent modification.

Botulinum neurotoxin A protease: discovery of natural product exosite inhibitors.

A new mechanistic class of BoNT/A zinc metalloprotease inhibitors, from Echinacea, exemplified by the natural product d-chicoric acid (I1) is disclosed. A detailed evaluation of chicoric acid's mechanism of inhibition reveals that the inhibitor binds to an exosite, displays noncompetitive partial inhibition, and is synergistic with a competitive active site inhibitor when used in combination. Other components found in Echinacea, I3 and I4, were also inhibitors of the protease.

[Synthesis and optimize reaction conditions of chlorogenic acid artificial antigen].

OBJECTIVE: To synthesize artificial antigen of the chlorogenic acid (CGA), a constituent in Traditional Chinese Medicine, then optimize the reaction conditions, so that to supply the basis in material and technique for study on Chinese medicine injection of adverse reactions in-depth. METHOD: The complete antigen of chlorogenic acid (CGA-BSA) was synthesized by CGA coupled to carrier protein bovine serum albumi (BSA) using carbodiimide method. We used the orthogonal design test to optimize reaction conditions and used the MALDI-TOF-MS and UV motheds to determine the coupling rate of the CGA-BSA. RESULT: The coupling rate were 20 and 18.8, counting by MALDI-TOF-MS and UV, respectively; while the best reaction conditions were NHS: CGA, EDC: CGA, CGA: BSA were 4: 1, 1: 1, 200: 1, respectively, with the pH 9. CONCLUSION: The complete antigen is preparated successfully. Which supplied the basis to advanced study of correlation.

Chlorogenic acid derivatives with alkyl chains of different lengths and orientations: potent alpha-glucosidase inhibitors.

Alpha-glucosidases play important roles in the digestion of carbohydrates and biosynthesis of viral envelope glycoproteins. Inhibitors of alpha-glucosidase are promising candidates for the development of antitype II diabetics and anti-AIDS drugs. Here, we report the synthesis and alpha-glucosidase inhibitory activity of mono- and diketal/acetal derivatives of chlorogenic acid. The diketal derivatives showed more potent inhibitory activity than the monoketals. The 1,7-(5-nonanone) 3,4-(5-nonanone)-chlorogenic acid diketal showed remarkable inhibitory activity against alpha-glucosidases with potency better than that of 1-deoxynojirimycin hydrochloride. Four diasteremers of pelargonaldehyde diacetal and two of monoacetal derivatives of chlorogenic acid were synthesized in this study. They showed significant potent inhibition similar to or more potent than the ketal counterparts. Acetals with the alkyl chain oriented toward position 2 of chlorogenic acid showed more potent activity than those oriented toward position 6.

Dicaffeoyltartaric acid analogues inhibit human immunodeficiency virus type 1 (HIV-1) integrase and HIV-1 replication at nontoxic concentrations.

The human immunodeficiency virus type 1 (HIV-1) is a major health problem worldwide. In this study, 17 analogues of L-chicoric acid, a potent inhibitor of HIV integrase, were studied. Of these analogues, five submicromolar inhibitors of integrase were discovered and 13 compounds with activity against integrase at less than 10 microM were identified. Six demonstrated greater than 10-fold selectivity for HIV replication over cellular toxicity. Ten analogues inhibited HIV replication at nontoxic concentrations. Alteration of the linkages between the two bis-catechol rings, including the use of amides, mixed amide esters, cholate, and alkyl bridges, was explored. Amides were as active as esters but were more toxic in tissue culture. Alkyl and cholate bridges were significantly less potent against HIV-1 integrase in vitro and were inactive against HIV-1 replication. Two amino acid derivates and one digalloylderivative of L-chicoric acid (L-CA) showed improved selectivity over L-CA against integration in cell culture. These data suggest that in addition to the bis-catechols and free carboxylic acid groups reported previously, polar linkages are important constituents for optimal activity against HIV-1 integrase and that new derivatives can be developed with increased specificity for integration over HIV entry in vivo.

Chlorogenic acid and synthetic chlorogenic acid derivatives: novel inhibitors of hepatic glucose-6-phosphate translocase.

The enzyme system glucose-6-phosphatase (EC 3.1.3.9) plays a major role in the homeostatic regulation of blood glucose. It is responsible for the formation of endogenous glucose originating from gluconeogenesis and glycogenolysis. Recently, chlorogenic acid was identified as a specific inhibitor of the glucose-6-phosphate translocase component (Gl-6-P translocase) of this enzyme system in microsomes of rat liver. Glucose 6-phosphate hydrolysis was determined in the presence of chlorogenic acid or of new synthesized derivatives in intact rat liver microsomes in order to assess the inhibitory potency of the compounds on the translocase component. Variation in the 3-position of chlorogenic acid had only poor effects on inhibitory potency. Introduction of lipophilic side chain in the 1-position led to 100-fold more potent inhibitors. Functional assays on isolated perfused rat liver with compound 29i, a representative of the more potent derivatives, showed a dose-dependent inhibition of gluconeogenesis and glycogenolyosis, suggesting glucose-6-phosphatase as the locus of interference of the compound for inhibition of hepatic glucose production also in the isolated organ model. Gl-6-P translocase inhibitors may be useful for the reduction of inappropriately high rates of hepatic glucose output often found in non-insulin-dependent diabetes.