Method development for β-glucogallin and gallic acid analysis: Application to urinary pharmacokinetic studies

Novel Emblica officinalis extract containing β-glucogallin vs. metformin: a randomized, open-label, comparative efficacy study in newly diagnosed type 2 diabetes mellitus patients with dyslipidemia

The efficacy of Emblica officinalis extract (EOE) containing 10% β-glucogallin was compared against metformin in newly diagnosed subjects with diabetic dyslipidemia which is a significant factor in cardiovascular disease. Daily administration with EOE-1 g, EOE-2 g, or metformin 500 mg for 90 days significantly decreased fasting blood sugar and postprandial blood sugar (FBS and PPBS), hemoglobin A1c (HbA1c) and lipid levels in all three treatment groups. The FBS, PPBS and HbA1c were significantly lower in the EOE-2 g group compared with metformin and EOE-1 g groups. The reductions in LDL and TC in the EOE-2 g group were also significantly higher than in the EOE-1 g group and were comparable to the metformin group. No serious adverse effects were observed in any study participants. EOE-1 g and 2 g day^-1 are safe and potent antidiabetic agents, with comparable efficacy to the pharmaceutical drug, metformin. Supplementation with EOE-2 g day^-1 showed greater efficacy than metformin in reducing circulating glucose levels.

Electrochemically activated pencil lead electrode as a sensitive voltammetric sensor to determine gallic acid

An electrochemical sensor for the determination of some polyphenolic compounds such as Gallic acid (GA) and Galloyl esters was developed using the activated pencil lead electrode (APLE). At first, a study has been made of the optimum conditions for electrochemical activation of the pencil lead electrode. Potentiodynamic and potentiostatic strategies were investigated for activation of the pencil lead electrode and the results show that the potentiodynamic pretreatment gives better performance toward measurement of the polyphenolic compounds. Electrochemical properties of GA were investigated using chronoamperometry and cyclic voltammetry; and some thermodynamic and kinetic variables such as α, n _α, and D were calculated. Sensitive differential pulse voltammetry (DPV) technique was applied for the determination of Gallic acid and Galloyl esters in different samples. Enhanced oxidation peak currents of Gallic acid were observed at APLE when compared with non-activated PLE. The calibration graph has two linear ranges of 0.49-24.3 µM and 0.07-0.83 mM, and the obtained limit of detection for S/N = 3 was 0.25 µM. Adsorptive stripping differential pulse voltammetry (AdSDPV) was also conducted to determine Gallic acid and Galloyl esters in sub-micromolar concentration range. Using the AdSDPV method, the limit of detection was improved and calculated to be 5.2 nM. The proposed method was successfully applied for quantification of the total concentration of Gallic acid and Galloyl esters in a variety of real samples such as black and green tea, and mango juice samples, and desirable recovery values indicated the good accuracy of the developed sensor.

Standardized Emblica officinalis fruit extract inhibited the activities of α-amylase, α-glucosidase, and dipeptidyl peptidase-4 and displayed antioxidant potential

BACKGROUND

Emblica officinalis, known as amla in Ayurveda, has been used as a folk medicine to treat numerous pathological conditions, including diabetes. However, the novel extract of E. officinalis fruit extract (amla fruit extract, AFE, Saberry®) containing 100 g kg^-1 β-glucogallin along with hydrolyzable tannins has not yet been extensively studied for its antidiabetic potential.

OBJECTIVE

The aim of this study was to investigate the antidiabetic and antioxidant activities of AFE and its stability during gastric stress as well as its thermostability.

METHODS

The effect of AFE on the inhibition of pancreatic α-amylase and salivary α-amylase enzymes was studied using starch and yeast α-glucosidase enzyme using 4-nitrophenyl α-d-glucopyranoside as substrate. Further, 2,2-diphenyl-1-picrylhydrazyl radical scavenging and reactive oxygen species inhibition assay was performed against AFE.

RESULTS

AFE potently inhibited the activities of α-amylase and α-glucosidase in a concentration-dependent manner with half maximal inhibitory concentration (IC₅₀ ) values of 135.70 μg mL^-1 and 106.70 μg mL^-1 respectively. Furthermore, it also showed inhibition of α-glucosidase (IC₅₀ 562.9 μg mL^-1 ) and dipeptidyl peptidase-4 (DPP-4; IC₅₀ 3770 μg mL^-1 ) enzyme activities. AFE is a potent antioxidant showing a free radical scavenging activity (IC₅₀ 2.37 μg mL^-1 ) and protecting against cellular reactive oxygen species (IC₅₀ 1.77 μg mL^-1 ), and the effects elicited could be attributed to its phytoconstituents.

CONCLUSION

AFE showed significant gastric acid resistance and was also found to be thermostable against wet heat. Excellent α-amylase, α-glucosidase, and DPP-4 inhibitory activities of AFE, as well as antioxidant activities, strongly recommend its use for the management of type 2 diabetes mellitus. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A simple ultrasensitive electrochemical sensor for simultaneous determination of gallic acid and uric acid in human urine and fruit juices based on zirconia-choline chloride-gold nanoparticles-modified carbon paste electrode

The determination of gallic acid (GA) and uric acid (UA) is essential due to their biological properties. Numerous methods have been reported for the analysis of GA and UA in various real samples. However, the development of a simple, rapid and practical sensor still remains a great challenge. Here, a carbon paste electrode (CPE) was modified by nanocomposite containing zirconia nanoparticles (ZrO₂NPs), Choline chloride (ChCl) and gold nanoparticles (AuNPs) to construct ZrO₂-ChCl-AuNPs/CPE as electrochemical sensor for the simultaneous electro-oxidation of GA and UA. Characterization was performed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The modified electrode was investigated by different methods including electrochemical impedance spectroscopy and cyclic voltammetry. Kinetic parameters such as charge transfer coefficient, standard heterogeneous electron transfer rate constant and other parameters were calculated via voltammetry techniques. Differential pulse voltammetry was used for simultaneous determination of GA and UA applying the ZrO₂-ChCl-AuNPs/CPE electrode. At the optimum conditions, this sensor showed a linear response in the ranges 0.22- 55 and 0.12-55 µM for GA and UA, respectively. In addition, low detection limits of 25 and 15 nM were obtained for GA and UA, respectively. Furthermore, ZrO₂-ChCl-AuNPs/CPE was successfully applied for the independent determination of GA in green tea and fruit juice as well as the simultaneous determination of GA and UA in human urine samples.

Development of an in vivo glucosylation platform by coupling production to growth: Production of phenolic glucosides by a glycosyltransferase of Vitis vinifera

Glycosylation of small molecules can significantly alter their properties such as solubility, stability, and/or bioactivity, making glycosides attractive and highly demanded compounds. Consequently, many biotechnological glycosylation approaches have been developed, with enzymatic synthesis and whole-cell biocatalysis as the most prominent techniques. However, most processes still suffer from low yields, production rates and inefficient UDP-sugar formation. To this end, a novel metabolic engineering strategy is presented for the in vivo glucosylation of small molecules in Escherichia coli W. This strategy focuses on the introduction of an alternative sucrose metabolism using sucrose phosphorylase for the direct and efficient generation of glucose 1-phosphate as precursor for UDP-glucose formation and fructose, which serves as a carbon source for growth. By targeted gene deletions, a split metabolism is created whereby glucose 1-phosphate is rerouted from the glycolysis to product formation (i.e., glucosylation). Further, the production pathway was enhanced by increasing and preserving the intracellular UDP-glucose pool. Expression of a versatile glucosyltransferase from Vitis vinifera (VvGT2) enabled the strain to efficiently produce 14 glucose esters of various hydroxycinnamates and hydroxybenzoates with conversion yields up to 100%. To our knowledge, this fast growing (and simultaneously producing) E. coli mutant is the first versatile host described for the glucosylation of phenolic acids in a fermentative way using only sucrose as a cheap and sustainable carbon source.