A rapid and reliable determination of doxycycline hyclate by HPLC with UV detection in pharmaceutical samples

An accurate, sensitive and reproducible high performance liquid chromatographic (HPLC) method for the quantification of doxycycline hyclate in pharmaceutical samples has been developed and validated. The drug and the standard were eluted from a Lichrosorb RP-8 (250 mm´4.6 mm, 10 mm particle size) at 20 °C with a mobile phase consisting of methanol, acetonitrile and 0.010 M aqueous solution of oxalic acid (2:3:5, v/v/v). The flow rate was 1.25 ml min-1. A UV detector set at 350 nm was used to monitor the effluent. Each analysis required no longer than 4 min. The limits of detection and quantification were 1.15 and 3.84 μg ml-1, respectively. Recoveries for different concentrations ranged from 99.58 to 101.93 %

Computational Studies on Selected Macrolides Active against Escherichia coli Combined with the NMR Study of Tylosin A in Deuterated Chloroform

Abstract: Although many antibiotics are active against Gram-positive bacteria, fewer also show activity against Gram-negative bacteria. Here, we present a combination of in silico (electron ion-interaction potential, molecular docking, ADMET), NMR, and microbiological investigations of selected macrolides (14-membered, 15-membered, and 16-membered), aiming to discover the pattern of design for macrolides active against Gram-negative bacteria. Although the conforma-tional studies of 14-membered and 15-membered macrolides are abundant in the literature, 16-membered macrolides, and their most prominent representative tylosin A, have received rela-tively little research attention. We therefore report the complete 1H and 13C NMR assignment of tylosin A in deuterated chloroform, as well as its 3D solution structure determined through mo-lecular modelling (conformational search) and 2D ROESY NMR. Additionally, due to the degra-dation of tylosin A in deuterated chloroform, other species were also detected in 1D and 2D NMR spectra. We additionally studied the anti-bacterial activity of tylosin A and B against se-lected Gram-positive and Gram-negative bacteria

Phenolic Profile and Antioxidant Activity of Pulp and Peel from Peach and Nectarine Fruits

Peach (Prunus persica L.) is a fruit of high nutritional and economic value. Carbohydrates, dietary fibers, minerals and organic acids are among the major constituents of peach fruit, which contribute to the nutritional quality of both fresh fruits and juice. Polyphenolic compounds found in peach may play an important role in physiological functions related to human health. Different polyphenolics may have varied biological activities including antioxidant activity. In this study antioxidant characteristics between peel and pulp of different peach cultivars (‘RadmilovÄanka’, ‘June Gold’, ‘Blake’, ‘Hale’, ‘Vesna’, ‘Adria’) and one of nectarine (‘Fantasia’) were investigated. The peel and pulp extracts showed a huge amount of total phenolics (TP), total flavonoids (TF), total hydroxycinnamates (TH) and total flavonols (TFL), ranging from 42.7-211.4, 11.1-128.5 mg GAE/100 g fresh weight (f.w.) (TP), 21.9 -94.9, 5.0-58.9 mg CE/100 g f.w. (TF), 28.4-389.2, 8.5-165.8 mg kg-1 f.w. (TH) and 17.3-54 mg kg-1 f.w. (TFL). High contents of phenolic compounds were significantly correlated with high antioxidant capacities. Peach pulp and peel differ significantly in their phenolic profiles: the pulp contains mainly chlorogenic, neochlorogenic and p-coumaric acids, whereas the peel possesses chlorogenic, neochlorogenic and p-coumaric acids together with several flavonol glycosides in huge amounts. Our results indicate that cultivar and extraction solvent play important roles in phenolic compositions and antioxidant properties of peach and nectarine extracts, which was shown using statistical analysis (ANOVA). There are high correlations between extracted phenolic compounds and peach and nectarine cultivars, and used solvent and part of the fruit (peel and pulp)

Selected Derivatives of Erythromycin B- In Silico and Anti-Malarial Studies

From MDPI via Jisc Publications RouterHistory: accepted 2021-11-12, pub-electronic 2021-11-18Publication status: PublishedFunder: Ministry of Education, Science and Technological Development of Republic of Serbia; Grant(s): 451-03-9/2021-14/200124Funder: National Research Foundation; Grant(s): 107881Erythromycin A is an established anti-bacterial agent against Gram-positive bacteria, but it is unstable to acid. This led to an evaluation of erythromycin B and its derivatives because these have improved acid stability. These compounds were investigated for their anti-malarial activities, by their in silico molecular docking into segments of the exit tunnel of the apicoplast ribosome from Plasmodium falciparum. This is believed to be the target of the erythromycin A derivative, azithromycin, which has mild anti-malarial activity. The erythromycin B derivatives were evaluated on the multi-drug (chloroquine, pyrimethamine, and sulfadoxine)-resistant strain K1 of P. falciparum for asexual growth inhibition on asynchronous culture. The erythromycin B derivatives were identified as active in vitro inhibitors of asexual growth of P. falciparum with low micro-molar IC50 values after a 72 h cycle. 5-Desosaminyl erythronolide B ethyl succinate showed low IC50 of 68.6 µM, d-erythromycin B 86.8 µM, and erythromycin B 9-oxime 146.0 µM on the multi-drug-resistant K1 of P. falciparum. Based on the molecular docking, it seems that a small number of favourable interactions or the presence of unfavourable interactions of investigated derivatives of erythromycin B with in silico constructed segment from the exit tunnel from the apicoplast of P. falciparum is the reason for their weak in vitro anti-malarial activities

Macrolides: properties, synthesis and applications/ Biljana Arsic, Predrag Novak, Jill Barber, Maria Grazia Rimoli, Goran Kragol, Federica Sodano.

Includes bibliographical references and index."Macrolides, a class of natural macrocyclic products, are among the most clinically important antibiotics. The authors introduce the different classes of macrolides and their derivatives, principles of their biological activity, as well as synthesis methods of macrolide antibiotics"--Provided by publisher.Arsic, Biljana / Barber, Jill / Novak, Predrag -- Kragol, Goran -- Novak, Predrag -- Sodano, Federica / Rimoli, Maria Grazia -- Frontmatter -- Preface -- Contents -- 1. The macrolide antibiotics and their semi-synthetic derivatives / 2. The semisynthetic routes towards better macrolide antibiotics / 3. Interactions of macrolides with their biological targets / 4. Hybrids of macrolides and nucleobases or nucleosides: synthetic strategies and biological results / Index1 online resourc

Mobilité de l'îlot de haute pathogénicité de Yersinia pseudotuberculosis

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

On Structure Descriptors Related with Intramolecular Energy of Alkanes

In an earlier work it was demonstrated that the Zenkevich index U provides a measure of the intramolecular energy of an organic molecule, and that– in the case of alkanes– it is related to the Wiener index. We now show that U is much closer related to the recently introduced variable Wiener index Wλ: Within sets of isomeric alkanes, the relation between U and Wλ is linear, the (U,Wλ)-points forming several, mutually parallel, lines. Each such line pertains to a group of isomers possessing a fixed number of methyl groups. There exists a critical value of the parameter λ for which all the (U,Wλ)-lines coalesce, in which case the relation between U and Wλ becomes independent of the number of methyl groups. Approximate analytical expressions for the (U,Wλ)-dependence are deduced.Publishe