Dependence of the solubility of natural flavonoids in water on the concentration of miramistin,polyvinylpyrrolidone, and human serum albumin

In organized media of the cationic surfactant miramistin and the polymers polyvinylpyrrolidone and human serum albumin, the solubility of natural flavonoids quercetin and rutin increased by one or two orders of magnitude. The increase was more significant for hydrophobic quercetin than for hydrophilic rutin. The solubility also depended on the structure and self-organization of molecules in organized media and the site of flavonoids in them. The calculated binding constants increased in the series polyvinylpyrrolidone < miramistin < human serum albumin.     

THE MITRA‐WAN FORESTRY MODEL: A DISCRETE‐TIME OPTIMAL CONTROL PROBLEM

In this paper, we present some new properties of the Mitra‐Wan forestry model written as a discrete‐time optimal control problem. For this problem, the set of stationary states is characterized. For the optimal long‐run management, we consider the following optimality criteria: average optimality, good control policies, bias optimality, and overtaking optimality. We establish relationships between these criteria and show that the value of average optimal policies is constant and equals the value in the optimal stationary state.     

Regularities of retention of benzoic acids on microdispersed detonation nanodiamonds in water-methanol mobile phases

The dependences of the retention of benzoic acids on microdispersed sintered detonation nanodiamond (MSDN) on the concentration of the organic solvent in the eluent and the temperature of the chromatographic column under conditions of high-performance liquid chromatography (HPLC) are investigated. It is found that in the investigated range of methanol concentrations, the acids are retained by different mechanisms: at methanol contents of the eluent lower than 85%, retention decreases with increasing methanol concentration and increases at higher concentrations of the organic solvent. It is shown that retention of benzoic acids on MSDN under these conditions depends on the dissociation constant of the investigated substances. A comparison is made between the properties of MSDN and analogous properties of porous graphitic carbon.     

The effect of complexation with biopolymers on the adsorption of quercetin on silica

It is shown that the interaction of polyvinylpyrrolidone and human serum albumin with a natural flavonoid quercetin in aqueous medium results in the formation of 1 : 1 supramolecular complexes. As a result of complexation, the optical and protolytic properties of the flavonoid change and its concentration in solution increases considerably. The adsorption of quercetin on silica particles in the presence of polymers is discussed.     

Physicochemical properties of quercetin and rutin in aqueous solutions of decamethoxin antiseptic drug

The effect of a cationic surfactant, Decamethoxin, on the physicochemical properties of structurally related natural flavonoids, quercetin and rutin, was studied by spectrophotometry. The spectral and protolytic properties and the solubility of quercetin and rutin strongly depend on the Decamethoxin concentration in solution. The presence of Decamethoxin in the solution favors the tautomeric transition of the enol form of quercetin to the keto form.     

The Potency of Seaweed Sulfated Polysaccharides for the Correction of Hemostasis Disorders in COVID-19

Hemostasis disorders play an important role in the pathogenesis, clinical manifestations, and outcome of COVID-19. First of all, the hemostasis system suffers due to a complicated and severe course of COVID-19. A significant number of COVID-19 patients develop signs of hypercoagulability, thrombocytopenia, and hyperfibrinolysis. Patients with severe COVID-19 have a tendency toward thrombotic complications in the venous and arterial systems, which is the leading cause of death in this disease. Despite the success achieved in the treatment of SARS-CoV-2, the search for new effective anticoagulants, thrombolytics, and fibrinolytics, as well as their optimal dose strategies, continues to be relevant. The wide therapeutic potential of seaweed sulfated polysaccharides (PSs), including anticoagulant, thrombolytic, and fibrinolytic activities, opens up new possibilities for their study in experimental and clinical trials. These natural compounds can be important complementary drugs for the recovery from hemostasis disorders due to their natural origin, safety, and low cost compared to synthetic drugs. In this review, the authors analyze possible pathophysiological mechanisms involved in the hemostasis disorders observed in the pathological progression of COVID-19, and also focus the attention of researchers on seaweed PSs as potential drugs aimed to correction these disorders in COVID-19 patients. Modern literature data on the anticoagulant, antithrombotic, and fibrinolytic activities of seaweed PSs are presented, depending on their structural features (content and position of sulfate groups on the main chain of PSs, molecular weight, monosaccharide composition and type of glycosidic bonds, the degree of PS chain branching, etc.). The mechanisms of PS action on the hemostasis system and the issues of oral bioavailability of PSs, important for their clinical use as oral anticoagulant and antithrombotic agents, are considered. The combination of the anticoagulant, thrombolytic, and fibrinolytic properties, along with low toxicity and relative cheapness of production, open up prospects for the clinical use of PSs as alternative sources of new anticoagulant and antithrombotic compounds. However, further investigation and clinical trials are needed to confirm their efficacy.     

Keto-Enol tautomerization of quercetin in solutions of a cationic surfactant,miramistin

Tautomeric transformations of quercetin in solutions of a cationic surfactant, miramistin, have been spectrophotometrically studied. It has been established that, at pH ≥ 6, monoanions of enol-form quercetin are irreversibly transformed into keto-form monoanions, with the rate of this process depending on surfactant concentration and solution pH. It has been shown that the enol tautomer of quercetin is more stable in aqueous solutions, while the ketone form is stabilized in miramistin-containing media. The apparent dissociation constants have been determined for the enol (pK _a ^a= 6.60) and ketone = 5.64) tautomeric forms of quercetin in micellar solutions of miramistin.