Kinetic Determination of Arsenic(III) as Inhibitor of Victoria Blue 4R Oxidation in Strong Acid Solution

A new selective, sensitive and simple kinetic method was developed for the determination of As3+ traces in solution on the basis of their inhibiting effect on Victoria blue 4R (VB) oxidation by KBrO3 in the presence of HCl. The reaction was followed spectrophotometrically at 596.3 nm. The detection limit was 50.00 ng cm–3. The relative error vas 4.2 % to 1.5 % for As3+ in the concentration range from 80.00 to 350.00 ng cm–3. Also, appropriate kinetic equations were formulated and the influence of different ions upon the reaction rate was studied. The developed procedure was successfully applied to the determination of As3+ in various model and real samples

Enzimska kinetička metoda za određivanje propranolol-hidrohlorida u farmaceutskim preparatima zasnovana na njegovom inhibitorskom delovanju na holinesterazu

Propranolol, a widely used beta-blocker, inhibits the hydrolysis reaction of enzyme cholinesterase. Measurements of the difference in rate of hydrolysis rate between uninhibited and inhibited reactions allow the development of a kinetic method for its determination. Both systems, enzyme-substrate-chromogen and enzyme-substrate-chromogen-inhibitor, were characterized through biochemical kinetic parameters (K-M, 0.326-0.330 mmol/L; V-max, 40.0-43.0 mu mol/Lmin). The inhibition type was recognized as competitive and the inhibition constant, Ki, was determined to be 22.60 mu mol/L. The detection and quantification limits were calculated as 0.004 and 0.0136 mu mol/L, respectively. Accuracy and precision of proposed methods were tested. The proposed method showed good sensitivity, selectivity, simplicity and rapidity, thus it is convenient for clinical applications.Za propranolol, često propisivani neselektivni beta blokator, utvrđeno je da inhibira reakciju enzimske hidrolize butiriltioholin-jodida, koja je katalizovana serumskom holinesterazom. Merenjem razlike u brzini osnovne i inhibitorske reakcije hidrolize u prisustvu propranolola kao inhibitora, moguće je razviti kinetičku metodu za određivanje propranolola. Oba sistema, enzim-supstrat-hromogen kao i enzim-supstrat-hromogen-inhibitor, okarakterisani su biohemijskim kinetičkim parametrima (KM, 0,326-0,330 mmol/L; Vmax, 40-42,99 μmol/L min), inhibicija je definisana kao kompetitivna i određena je konstanta inhibicije 22,60 μmol/L. Da bi se u potpunosti iskoristile sve mogućnosti predložene metode u pogledu osetljivosti, tačnosti, preciznosti i selektivnosti, optimizovani su reakcioni uslovi. Konstruisana je kalibraciona prava, izračunata odgovarajuća jednačina i određeni granica detekcije i kvantifikacije i to 0,004 i 0,0136 μmol/L, redom. Tačnost i preciznost predložene metode su ispitane za tri koncentracije propranolola u oblasti kalibracione prave (0,082-21,120 μmol/L) u pet ponavljanja. Takođe, ispitan je uticaj većeg broja supstanci koje se mogu naći u uzorku na brzinu reakcije. Optimizovana metoda je primenjena za određivanje propranolola u farmaceutskim preparatima. Tačnost predložene metode je ispitana primenom metode standardnog dodatka. Predložena metoda ima dobru osetljivost, selektivnost, jednostavna je i brza, i nadasve lako dostupna, i na taj način primenljiva u velikom broju laboratorija

ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF THE ESSENTIAL OIL AND SOLVENT EXTRACTS OF MENTHA PULEGIUM L.

We report the total phenolic (TPC; expressed as gallic acid equivalents, GAE, per milligram of dry extract weight) and the total flavonoid contents (TFC; expressed as quercetin equivalents, QE, per milligram of dry extract weight) and antimicrobial and antioxidant activities of the essential oil and hexane, diethyl ether, ethyl acetate and methanol extracts of Mentha pulegium L. (Lamiaceae) collected in Serbia. The total phenolic content was in the range of 129.43-388.29 μg GAE/mg, while TFC ranged from 57.81 to 160.94 QE/mg; the highest TPC and TFC were found in the methanol extract. The antimicrobial activity (against five bacteria and two fungi species) of the essential oil and solvent extracts was assessed using disc-diffusion method. However, the studied samples demonstrated a poor antimicrobial potential. The antioxidant activity was screened using five different tests: 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid radical cation decolorization assay (ABTS), total reducing power (TRP), ferric reducing antioxidant power (FRAP) and cupric reducing antioxidant capacity assay (CUPRAC); the methanol extract showed the strongest antioxidant potential. The results of the different antioxidant assays were correlated mutually and with the total flavonoid and total phenolic contents (regression analysis and agglomerative hierarchical clustering). ANTIOKSIDANTNA I ANTIMIKROBNA AKTIVNOST ETARSKOG ULJA I EKSTRAKATA BILJNE VRSTE MENTHA PULEGIUM L.U ovom radu je određen sadržaj ukupnih fenola (TPC; izražen u ekvivalentima galne kiseline, GAE, po miligramu suvog biljnog ekstrakta) i ukupnih flavonoida (TPC; izražen u ekvivalentima kvarcetina, QE, po miligramu suvog biljnog ekstrakta), kao i antimikrobna i antioksidantna aktivnost etarskog ulja i heksanskog, dietil-etarskog, etil-acetatnog i metanolnog ekstrakta biljne vrste Mentha pulegium L. (Lamiaceae; populacija iz Srbije). Sadržaj ukupnih fenola analiziranih uzoraka se kretao u opsegu od 129,43 do 388,29 μg GAE/mg, dok je TFC bio u interval od 57,81 do 160,94 QE/mg; najviše vrednosti za TPC i TFC nađene su za metanolni ekstrakt. Antimikrobna aktivnost (prema pet bakterijskih i dva soja gljivica) etarskog ulja i ekstrakata je određena disk-difuzionom metodom. Proučavani uzorci su imali slabu antimikrobnu aktivnost. Antioksidantna aktivnost je ispitivana pomoću DPPH (2,2-difenil-1-pikrilhidrazil radikal), ABTS (2,2'-azino-bis(3-etilbenzotijazolin-6-sulfonska kiselina radikal katjon), TRP (ukupna redukciona sposobnost), FRAP (sposobnost redukcije feri-jona) i CUPRAC (sposobnost redukcije Cu(II)-jona) metodama; najviši antioksidantni potencijal je imao metanolni ekstrakt. Rezultati različitih metoda za određivanje antioksidantnog potencijala su korelisani međusobno, kao i sa sadržajem ukupnih fenola i flavonoida (regresiona analiza i aglomerativna hijerarhijska klaster analiza). HIGHLIGHTSThe essential oil and hexane, diethyl ether, ethyl acetate and methanol extracts of Mentha pulegium L. collected in Serbia were studied.Their total phenolic content was in the range of 129.43-388.29 μg GAE/mg, while total flavonoid content ranged from 57.81 to 160.94 QE/mg.Solvent extracts (SE) and essential oil of the studied M. pulegium population were poor antimicrobials.Antioxidant activities of SE were studied using five different methods.Differences between the previous and the present results suggest M. pulegium metabolic profile might be influenced by both genetic and environmental factors

A modification of the kinetic determination of pancuronium bromide based on its inhibitory effect on cholinesterase

A modification of the existing spectrophotometric kinetic method for the determination of pancuronium bromide (PCBr), based on pooled human serum cholinesterase (ChE, EC 3.1.1.8 acylcholine acylhydrolase) inhibition, was developed. Butyrylthiocholine iodide (concentration 1.667 mmol/L) was used as substrate and determination was performed at pH 7.6. Essential basic kinetic parameters were also determined: Michaelis-Menten's constant K-M=0.33 mmol/L, maximal reaction rate V-max=42.29 mu mol/ L min, inhibition constant K-I = 0.34 mu mol/L, and IC50=0.235 mu mol/L. Linear dependence between the reaction rate and the inhibitor concentration exists in PCBr concentration range 8.29-265.28 nmol/L, which corresponds to the real sample concentrations from 0.166 to 5.306 mu mol/L. The method detection limit was established to be 1.86 nmol/L and the quantification limit was 6.18 nmol/L. Precision of the method was tested for three pancuronium concentrations (16.58, 99.48, and 198.96 nmol/L). The relative standard deviation (RSD) was in the range 0.78-5.13%. Accuracy was examined by the standard addition method. The influence of substances usually present in serum and urine on the reaction rate was determined. The method developed was applied for PCBr determination in spiked serum and urine samples and in the urine taken during surgery. The method was proven to have good sensitivity, accuracy, and precision and can be considered suitable for clinical practice

Cholinesterase inhibition based determination of pancuronium bromide in biological samples

Pancuronium bromide (PCBr) inhibition effect on enzyme cholinesterase from pooled human serum (Che, EC 3.1.1.8 acylcholine acylhydrolase) was used for development of a spectrophotometric kinetic method for PCBr determination in human serum and urine. Optimal conditions for the basic and inhibitor reactions were established: pH=7.7 and substrate concentration c(benzoylcholine chloride)=1.33 mmol/L. Kinetic parameters were also determined: Michaelis-Menten's constant K-M=0.40 mmol/L, maximal reaction rate V-max=52.2 mu mol/L min, inhibition constant K-i=0,56 mu mol/L and IC50=1.31 mu mol/L. Linear dependence between the reaction rate and inhibitor concentration exists in PCBr concentration range 8.20-68.25 nmol/L, which corresponds to the real sample concentrations from 0.328 to 2.730 mu mol/L. The method detection and quantification limits were 2.01 nmol/L and 6.67 nmol/L, respectively. Precision of the method was tested for three pancuronium concentrations (10.70, 29.35 and 51.25 nmol/L). Relative standard deviation (RSD) was in the range 0.15-7.45%. Accuracy was examined by standard addition method. Influence of the substances usually present in serum and urine on the reaction rate was tested. The developed method was applied for PCBr content determination in serum model samples, urine model samples and in urine taken during surgery. The method has good sensitivity, accuracy, precision and it is suitable for clinical practice

Enzymatic kinetic method for determination of propranolol hydrochloride in pharmaceuticals based on its inhibitory effect on cholinesterase

Propranolol, a widely used beta-blocker, inhibits the reaction of enzyme cholinesterase hydrolysis. Measurements of the hydrolysis rate differences between and inhibited reactions, allows the development of a kinetic method for its determination. Both systems, enzyme-substrate-chromogen and enzyme-substrate-chromogen-inhibitor, were characterized through biochemical kinetic parameters (KM = 0.326-0.330 mmol/L; Vmax = 40-42.99 μmol/Lmin), inhibition type was recognized as competitive, and inhibition constant, Ki, was determined to be 22.60 μmol/L. The detection and quantification limits were calculated as 0.004 and 0.0136 μmol/L, respectively. Accuracy and precision of proposed methods were tested. Proposed method is characterized with good sensitivity, selectivity, simplicity and rapidity, thus it is convenient for clinical applications

Update on element content profiles in eleven wild edible mushrooms from family Boletaceae

The aim of this study was to determine and evaluate the amounts of major elements (Ca, Fe, K, Na and P), essential trace elements (Cu, Zn, Fe and Mn) and some other trace metals (Ag, Al, Co, Ni, Cr, Sr, Se, Bi, Rb) in eleven species of wild-grown common edible mushrooms from family Boletaceae (Boletus appendiculatus, Boletus edulis, Boletus regius, Boletus fechtneri, Boletus impolitus, Boletus purpureus, Boletus rhodoxanthus, Leccinum crocipodium, Leccinum pseudoscaber, Xerocomellus chrysenteron, Xerocomus badius) from Serbia. The measurements of major elements (Ca, Fe, K, Na and P) were carried out by inductively coupled plasma optical emission spectrometer (ICP-OES), while analytical measurements of the rest of studied elements were performed using an inductively coupled plasma mass spectrometer (ICP-MS), after microwave digestion. The results showed that the element concentrations were species-dependent. Potassium and phosphorous concentrations were found to be greater than those of the other mineral constituents in all tested species. Multivariate analysis included principal component analysis (PCA) and hierarchical cluster analyses (HCA). HCA grouped mushrooms in three statistically significant clusters, while PCA indicated connection between analyzed metals. Also, this paper highlights the importance of essential and nonessential elements of human health and their daily intake

Effects of solvent extraction system on antioxidant activity of Lamium purpureum L.

Antioxidant and free radical scavenging activity of methanol, ethanol, ethyl acetate and chloroform extracts of aerial parts of Lamium purpureum L. was determined by DPPH, ABTS, FRAP and TRP assays. Contents of flavonoids and phenols were also investigated. The total phenolic content in the extracts, determined using Folin–Ciocalteu assay, ranged between 8.57 to 128.00 mg GAE/g d.e. while concentrations of flavonoids in the extracts varied from 24.20 to 39.80 mg QuE/g d.e. The highest phenolic content was found in methanol extract (128.00 mg GAE/g d.e.). The highest content of total flavonoids was identified in the methanol extract (39.80 mg QuE/g d.e.) and the lowest was in the chloroform (24.30 mg QuE/g d.e.). DPPH scavenging of the extracts was determined and obtained IC50 values ranged from 0.12 to 3.12 mg/mL of solution. The values of ABTS radical scavenging activity ranged from 0.35 to 1.80 mg AA/g. The highest ABTS antiradical activity was registered for methanol extract. The FRAP value was found within the range 0.08 to 1.04 μmol Fe/mg. The best radical scavenger was methanol (1.04 μmol Fe/mg). In reducing power assay different extracts of L. purpureum showed increasing of activity with increased concentration, and all extracts possessed substantial dose dependent antioxidant activity. The best reducing capacity was obtained with methanol extract of L. purpureum (0.0132 mg AA/mL). The results in this study confirmed that L. purpureum possesses moderate antioxidant properties

Evaluation of antioxidant activity of Melittis melissophyllum L. extracts

The antioxidant activities of methanol and ethanol (10%, 30%, 50% and 96%) extracts of the aerial parts of Melittis melissophyllum L. were determined by DPP H, ABTS and FRAP assays. The content of flavonoids and phenols was also investigated. The total phenolic content in the extracts was determined using Folin-Ciocalteu assay; their amounts ranged between 63.5 and 111.7 mg GAeqv/g, while the concentrations of flavonoids were from 7.33 to 56.00 mg Queqv/g. IC50 values of the DPP H scavenging effect were from 0.109 to 0.664 mg/mL. The DPP H scavenging effect of the extracts was determined and the obtained IC50 values were from 0.109 to 0.664 mg/mL of solution. The values of ABTS radical activity were from 0.45 to 0.89 mg ascorbic acid/g. The FRAP value was within the range 0.160-0.382 mmol Fe/mg. The obtained values were analyzed by means of multivariate analysis, employing a hierarchical cluster analysis and between-groups linkage. The presented results confirmed that M. melissophyllum possesses good antioxidant properties and may serve as a promising source of natural antioxidants. [Projekat Ministarstva nauke Republike Srbije, br. 173029

First Report about Mineral Content, Fatty Acids Composition and Biological Activities of Four Wild Edible Mushrooms

The goal of this research was a comprehensive analysis of four wild edible mushroom species, Cantharellus cinereus, Clavariadelphus pistillaris, Clitocybe nebularis and Hygrocybe punicea, which have not been analyzed so far. Extracts of different polarities have been prepared and evaluated for their antioxidant activities by DPPH, ABTS, FRAP, TRP and CUPRAC methods. For all extracts, total phenolic content was determined. Based on the analysis, it was shown that solvent type had a significant effect on the antioxidant capacities of mushroom extracts, so water extracts showed the highest activity. Furthermore, the analysis includes determination of mineral composition, fatty acid profiles and antimicrobial activity. Unsaturated fatty acids, which are very important for human health, are dominant in the studied mushroom species. Linoleic and oleic acid consist of over 50 % of the total fatty acid composition. Seventeen biologically important and toxic elements have been analyzed by ICP-OES and ICP-MS and results showed that the element concentrations were species-dependent. Also, it has been found that analyzed mushrooms did not show any antimicrobial activity. Chemometric analysis was used to understand the connection between the extracts of different polarities.Peer-reviewed manuscript: [http://cherry.chem.bg.ac.rs/handle/123456789/2871