Determination of Diosmin in Pharmaceutical Products with Chemically Modified Voltammetric Sensors

In this paper, the electrochemical behavior of two types of sensors based on modified screen-printed electrodes (one screen-printed electrode based on carbon (SPCE) and another screen-printed electrode modified with Prussian Blue (PB/SPCE)) was studied with the aim of sensitive detection of diosmin, an active pharmaceutical compound from the class of flavonoids. The scan electron microscopy technique was used for the morphological characterization of PB/SPCE. The preliminary analysis assessed the electrochemical behavior of SPCE and PB/SPCE in KCl solution and in a double solution of potassium ferrocyanide-potassium chloride. It was shown that the active area of PB/SPCE is superior to the one of SPCE, the greater sensitivity being related with the presence of the electroactive modifier. Similarly, in the case of diosmin detection, the PB/SPCE sensor detect more sensitivity the diosmin due to the electrocatalytic effect of PB. From the study of the influence of reaction rate on the sensor's electrochemical response, it was shown that the detection process is controlled by the adsorption process, the degree of surface coverage with electroactive molecules being higher in the case of PB/SPCE. From the PB/SPCE calibration curve, it wasdetermined that it has high sensitivity and low detection and quantification limit values (limit of detection 5.22 × 10^-8 M). The applicability of the PB/SPCE sensor was confirmed by sensitive analysis of diosmin in pharmaceutical products. The voltammetric method is suitable for the detection and quantification of diosmin in pharmaceutical products. The method is simple, accurate, and quick and can be used in routine analysis in the examination of the quality of pharmaceutical products and other types of samples.

Thermodynamics of the Interaction between the Spike Protein of Severe Acute Respiratory Syndrome Coronavirus-2 and the Receptor of Human Angiotensin-Converting Enzyme 2. Effects of Possible Ligands

Since the end of 2019, the coronavirus SARS-CoV-2 has caused more than 1000000 deaths all over the world and still lacks a medical treatment despite the attention of the whole scientific community. Human angiotensin-converting enzyme 2 (ACE2) was recently recognized as the transmembrane protein that serves as the point of entry of SARS-CoV-2 into cells, thus constituting the first biomolecular event leading to COVID-19 disease. Here, by means of a state-of-the-art computational approach, we propose a rational evaluation of the molecular mechanisms behind the formation of the protein complex. Moreover, the free energy of binding between ACE2 and the active receptor binding domain of the SARS-CoV-2 spike protein is evaluated quantitatively, providing for the first time the thermodynamics of virus-receptor recognition. Furthermore, the action of different ACE2 ligands is also examined in particular in their capacity to disrupt SARS-CoV-2 recognition, also providing via a free energy profile the quantification of the ligand-induced decreased affinity. These results improve our knowledge on molecular grounds of the SARS-CoV-2 infection and allow us to suggest rationales that could be useful for the subsequent wise molecular design for the treatment of COVID-19 cases.

Ultrasound-Assisted Extraction of Taxifolin, Diosmin, and Quercetin from Abies nephrolepis (Trautv.) Maxim: Kinetic and Thermodynamic Characteristics

Extraction behaviors of the 3 flavonoids taxifolin, diosmin, and quercetin have been investigated in Abies nephrolepis leaves and bark. The following operation parameters—ethanol volume fraction, liquid–solid ratio, temperature, ultrasound irradiation power and time, and ultrasound frequency—were varied to study their effect on the yield of the 3 flavonoids during extraction. The results showed that a low extraction efficiency occurred at 293.15 K due to slow kinetics, while the situation was significantly improved at 333.15 K. The kinetic data for the extraction yields of the 3 flavonoids achieved good fits by the first-order kinetic model. From the thermodynamic analysis results, we realized that the ultrasound-assisted extraction of taxifolin, diosmin, and quercetin from the leaves and bark of A. nephrolepis was a spontaneous and endothermic process in which the disorder increased (ΔG⁰ < 0, ΔH⁰ > 0, and ΔS⁰ > 0). According to the response surface methodology (RSM) analysis, under the optimal operation conditions (ethanol concentration of 50%, liquid–solid ratio of 20 mL/g, frequency of 45 kHz, extraction time of 39.25 min, ultrasound irradiation power of 160 W and temperature of 332.19 K), the total yield of the 3 flavonoids were 100.93 ± 4.01 mg/g from the leaves of A. nephrolepis (with 31.03 ± 1.51 mg/g, 0.31 ± 0.01 mg/g, 69.59 ± 2.57 mg/g for taxifolin, diosmin, and quercetin, respectively), and under the optimal operation conditions (ethanol concentration of 50%, liquid–solid ratio of 20 mL/g, frequency of 45 kHz, extraction time of 36.80 min, ultrasound irradiation power of 150 W and temperature of 328.78 K), 16.05 mg/g ± 0.38 mg/g were obtained from the bark of A. nephrolepis (with 1.44 ± 0.05 mg/g, 0.47 ± 0.01 mg/g, 14.14 ± 0.38 mg/g for taxifolin, diosmin, and quercetin, respectively), which were close to the prediction values.

Preparation, evaluation and pharmacokinetics of diosmin herbosome in beagle dogs

Diosmin is one of the most widely used phlebotonic drugs, but its poor bioavailability has restricted its usage. The aim of this study was to formulate a complex Diosmin with phospholipids (75% in PC, in 1:2 molar ratios) and to evaluate for solubility, drug content, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and in vitro dissolution study. Further to test the bioavailability of both the complex and Alvenor⌖ in beagle dogs and compare pharmacokinetic parameters. Diosmin herbosome was found to be more soluble than both pure diosmin and Alvenor⌖. The complex contained 71.94% drug content. DSC thermograms and XRD also proved the claim of the complexation. The dissolution profile of diosmin herbosome and Alvenor⌖ in water-ethanol medium showed an increase of the dissolution for diosmin herbosome. Comparison of plasma concentration and main pharmacokinetic parameters of diosmin herbosome treated and Alvenor⌖ treated dogs showed a higher C_max for the complex with longer elimination half-life. The complexation of diosmin with phospholipids can be potentially used in enhancing the absorption and solubility, consequently increasing the bioavailability of the drug.

Comparative Bioavailability of Two Diosmin Formulations after Oral Administration to Healthy Volunteers

Diosmin is a flavonoid commonly found in citrus fruits, largely used as adjuvant treatment for circulatory disorders, including chronic venous insufficiency (CVI) and hemorrhoids. Following oral administration, diosmin is not directly absorbed but must first be hydrolyzed into its aglycone, diosmetin, which is then absorbed into the systemic circulation. The aim of the current cross-over clinical study was to assess the pharmacokinetic profile of µSmin^® Plus, a micronized diosmin flavonoid complex standardized in diosmin and formulated with a buffering agent (tested formulation). The study compared this to unformulated micronized diosmin (reference), in 16 healthy volunteers. Plasma samples were analyzed by HPLC-MS and plasma diosmetin concentration was measured after deconjugation with β-glucuronidase. For the tested formulation area under the curve (AUC_0-t), and maximum plasma and time concentration (C_max; t_max) were found to be 298.4 ± 163.7, 50.3 ± 22.6 and 2.2 ± 2.9, respectively. AUC_0-t and C_max of the reference were 31.9 ± 100.4 and 2.4 ± 1.9, respectively. The tested formulation showed higher plasmatic concentrations of diosmetin in comparison to those obtained after the administration of unformulated micronized diosmin. The relative bioavailability was 9.4 greater for the tested formulation than in micronized diosmin. In conclusion, our data indicate that µSmin^® Plus was rapidly and well absorbed into systemic circulation and may therefore be ideally suitable to deliver diosmin in human interventional trials.

In vitro effects of diosmin, naringenin, quercetin and indole-3-carbinol on fish hepatic CYP1A1 in the presence of clotrimazole and dexamethasone

Phytochemicals are widely present in fruits, vegetables and other plants and have great health benefits owing to their antioxidant properties. They are naturally found in the aquatic environment as well as discharged from sewage treatment plants after their large consumption. Little is known about their impact on fish; particularly in light of their interactions with pharmaceuticals. Therefore, this study was designed to determine the effects of diosmin, naringenin, quercetin and idole-3-carbinol on CYP1A-dependent 7-ethoxyresorufin-O-deethylase (EROD) activity on rainbow trout hepatic microsomes in the presence of two pharmaceuticals: clotrimazole and dexamethasone. The interactions between the phytochemicals and pharmaceuticals used in this study were determined using a combination index. Hepatic microsomes were exposed to two concentrations (1-or 50 μM) of phytochemicals and pharmaceuticals separately and in combinations. Singly, clotrimazole inhibited EROD activity 40% and 90% of control, while dexamethasone did not. Naringenin and diosmin inhibited EROD activity alone up to 90% and 55% respectively, but activities were further inhibited in the presence of either pharmaceutical. The preliminary study of combinations of clotrimazole with phytochemicals primarily showed synergistic effects. While EROD activity was not inhibited in the presence of quercetin or indole-3-carbinol, significant and synergistic inhibition was detected when either of these was combined with clotrimazole or dexamethasone.

Diosmin/essential oil combination for dermal photo-protection using a lipoid colloidal carrier

Solar irradiation induces skin inflammatory processes causing deleterious effects like premature ageing. In this study, the designed lipoid colloidal carrier (LCC) was loaded with Diosmin in combination with different essential oils, to be used as a topical photo-protective preparation. To investigate the ability of the essential oils to potentiate Diosmin effects, the Diosmin/essential oil-loaded LCCs (LCC2, LCC3 and LCC4) were compared to the Diosmin-loaded LCC (LCC1). The incorporated essential oils were those of Rosmarinus officinalis, Zingiber officinale or Vitis vinifera in LCC2, LCC3 and LCC4, respectively. All the LCCs had particle size (PS) values ranging from 121.1 to 144.3nm with uniform distribution and, zeta potential (Z) values around 30mV. Also, they all had high drug encapsulation efficiencies. LCC1 had the lowest anti-oxidant and in-vitro sun-blocking effect (p<0.05). In-vivo photo-protective studies showed that all the formulated LCCs had a skin protective effect when compared to the positive control (p<0.05); however LCC1 had the lowest anti-erythemal and anti-wrinkling effect. Histological studies proved the efficacy of the designed LCCs as skin anti-photoageing, with LCC1 showing the lowest anti-inflammatory and anti-wrinkling effect, while LCC2 had the highest anti-wrinkling effect. These results indicated that the suggested Diosmin/essential oil combinations improved the anti-oxidant, sun-blocking and anti-photoageing effects of Diosmin. After one year of storage, the LCCs showed satisfactory physical stability. This study presents the designed LCCs as safe and effective nano-structured dermal care products containing 'all-natural' components.

Pharmacokinetic Profile of µSMIN Plus™, a new Micronized Diosmin Formulation, after Oral Administration in Rats

Diosmin is a naturally occurring flavonoid present in citrus fruits and other plants belonging to the Rutaceae family. It is used for the treatment of chronic venous insufficiency (CVI) for its pheblotonic and vaso-active properties, safety and tolerability as well. The aim of the current in vivo study was to investigate the pharmacokinetic profile of a branded micronized diosmin (µSMIN Plus™) compared with plain micronized diosmin in male Sprague-Dawley rats. After oral administration by gastric gavage, blood samples were collected via jugular vein catheters at regular time intervals from baseline up to 24 hours. Plasma concentrations were assessed by LC/MS. For each animal, the following pharmacokinetic parameters were calculated using a non-compartmental analysis: maximum plasma drug concentration (Cmax), time to reach Cmax (Tmax), area under the plasma concentration-time curve (AUC0-last), elimination half-life (t½), and relative oral bioavailability (%F). The results of the current study clearly showed an improvement in the pharmacokinetic parameters in animals treated with µSMIN Plus™ compared with animals treated with micronized diosmin. In particular, µSMIN Plus™ showed a 4-fold increased bioavailability compared with micronized diosmin. In conclusion, the results from the current study provided a preliminary pharmacokinetic profile for µSMIN Plus™, which may represent a new tool for CVI management.

Enhancement of the water solubility of flavone glycosides by disruption of molecular planarity of the aglycone moiety

Enhancement of the water solubility by disruption of molecular planarity has recently been reviewed as a feasible approach in small-molecule drug discovery programs. We applied this strategy to some natural flavone glycosides, especially diosmin, a highly insoluble citroflavonoid prescribed as an oral phlebotropic drug. Disruption of planarity at the aglycone moiety by 3-bromination or chlorination afforded 3-bromo- and 3-chlorodiosmin, displaying a dramatic solubility increase compared with the parent compound.

[Study on chemical constituents of Hyssopus cuspidatus]

OBJECTIVE

To study the chemical constituents of Hyssopus cuspidatus.

METHODS

Compounds were isolated and purified by extraction and different kinds of column chromatography. Their structures were determined on the basis of the physicochemical properties and spectral analysis.

RESULTS

Six compounds were identified as caffeic acid methyl ester (1), luteolin 7-O-alpha-L-rhamnopyranosyl (1 --> 6)-beta-D-glucopyranoside (2), luteolin 7-O-beta-D-glucuronide (3), diosmin (4), acacetin 7-O-alpha-L-rhamnopyranosyl(1 --> 6)-beta-D-glucopyranoside (5) and rosmarinic acid (6).

CONCLUSION

Compounds 1, 4 and 6 are isolated from this plant for the first time, and compounds 2, 3 and 5 are firstly obtained from Hyssopus genus.

[Chemical constituents contained in seeds of Notopterygium franchetii]

OBJECTIVE

To study the chemical constituents from the seeds of Notopterygium franchetii.

METHOD

Ethanol extracts of seeds N. franchetii were separated and purified by such methods as normal and reversed phase column chromatographies and thin-layer chromatography and structurally elucidated by MS and NMR evidences.

RESULT

Twenty nine compounds were separated, they were isoimperatorin (1), [3-sitosterol (2), phellopterin (3), bergapten (4), N-tetra, hexa, octacosanoylanthranilic acid (5-7), daucosterol (8), oxypeucedanin hydrate (9), umbelliferone (10), demethylfuropinnarin (11), (2S, 3S, 4R, 8E)-2-[(2'R)- 2'-hydroxydoco, trico, tetraco, entaco, hexaco sanosylamino] -octadecene-1, 3, 4-triol (12-16), (-)-oxypeucedanin (17), diosmetin (18), bergaptol-O-beta-D-glucopyranoside (19), nodakenin (20), 1'-O-beta-D-glucopyranosyl-(2R, 3S)-3-hydroxynodakenetin (21), uracil (22), decuroside V (23), 8-O-beta-D-glucopyranosyl-5-hydroxypsoralen (24), 8-O-beta-D-glucopyranosyl-5-methoxylpsoralen (25), diosmin (26), alaschanioside C (27), kynurenic acid (28) and mannitol (29).

CONCLUSION

All of these compounds were separated from the seeds of N. franchetii for the first time. Of them, 18, 22, 26 and 29 were firstly obtained from genus Notopterygium.

Flavonoid-mediated presenilin-1 phosphorylation reduces Alzheimer's disease beta-amyloid production

Glycogen synthase kinase 3 (GSK-3) dysregulation is implicated in the two Alzheimer's disease (AD) pathological hallmarks: beta-amyloid plaques and neurofibrillary tangles. GSK-3 inhibitors may abrogate AD pathology by inhibiting amyloidogenic gamma-secretase cleavage of amyloid precursor protein (APP). Here, we report that the citrus bioflavonoid luteolin reduces amyloid-beta (Abeta) peptide generation in both human 'Swedish' mutant APP transgene-bearing neuron-like cells and primary neurons. We also find that luteolin induces changes consistent with GSK-3 inhibition that (i) decrease amyloidogenic gamma-secretase APP processing, and (ii) promote presenilin-1 (PS1) carboxyl-terminal fragment (CTF) phosphorylation. Importantly, we find GSK-3alpha activity is essential for both PS1 CTF phosphorylation and PS1-APP interaction. As validation of these findings in vivo, we find that luteolin, when applied to the Tg2576 mouse model of AD, decreases soluble Abeta levels, reduces GSK-3 activity, and disrupts PS1-APP association. In addition, we find that Tg2576 mice treated with diosmin, a glycoside of a flavonoid structurally similar to luteolin, display significantly reduced Abeta pathology. We suggest that GSK-3 inhibition is a viable therapeutic approach for AD by impacting PS1 phosphorylation-dependent regulation of amyloidogenesis.

Determination of trace levels of diosmin in a pharmaceutical preparation by adsorptive stripping voltammetry at a glassy carbon electrode

A systematic study on the electrochemical behavior of diosmin in Britton-Robinson buffer (pH 2.0-10.0) at a glassy carbon electrode (GCE) was made. The oxidation process of the drug was found to be quasi-reversible with an adsorption-controlled step. The adsorption stripping response was evaluated with respect to various experimental conditions, such as the pH of the supporting electrolyte, the accumulation potential and the accumulation time. The observed anodic peak current at +0.73 V vs. Ag/AgCl reference electrode increased linearly over two orders of magnitude from 5.0x10(-8) M to 9.0x10(-6) M. A limit of detection down to 3.5x10(-8) M of diosmin at the GCE was achieved with a mean recovery of 97+/-2.1%. Based on the electrochemical data, an open-circuit accumulation step in a stirred sample solution of BR at pH 3.0 was developed. The proposed method was successfully applied to the determination of the drug in pharmaceutical formulations. The results compared favorably with the data obtained via spectrophotometric and HPLC methods.

Micronized purified flavonoid fraction (MPFF): a review of its pharmacological effects, therapeutic efficacy and benefits in the management of chronic venous insufficiency

Initially, the progression of chronic venous insufficiency is related to venous hypertension. The earliest complaints or symptoms, as well as vessel wall deterioration, valve restructuring, and, eventually, varicose veins, result not only from elevation of pressure, but also from a cascade of biochemical events related to both the macro- and the microcirculation. Thickening and remodelling of the venous wall are influenced by two parameters: abnormal shear stress and hypoxia that activate the endothelium first at the level of valve cusps and then in large veins. Hypoxia leads to activation of the endothelium and leukocyte accumulation. By inhibiting endothelial activation, micronized purified flavonoid fraction (MPFF) (Daflon 500 mg), an edema-protective agent, can prevent the inflammatory cascade resulting from the leukocyte-endothelium interaction. This subsequently delays the appearance of reflux and inhibits the initiation of the vicious circle ending in enhanced venous pressure. This is how Daflon 500 mg relieves patients from symptoms and edema and possibly also prevents the appearance of varicose veins. Rheological disturbances also play a major role in the appearance of these disorders. Furthermore, venous hypertension provokes leakage from the vessels and capillaries exhibiting increased permeability, leading to increases in hydrostatic load, and overloading of the lymphatic network, which subsequently results fluid exudation causing edema. Microcirculatory dysfunction leads to capillary damage, skin changes and venous leg ulcers. The clinical efficacy of Daflon 500 mg in venous leg ulcers has been demonstrated by several randomised controlled studies, in which the rate of ulcer healing was significantly shortened. An explanation for the ability to speed ulcer healing comes from the protection Daflon 500 mg exerts on the microcirculation.

Semisynthesis of linarin, acacetin, and 6-iodoapigenin derivatives from diosmin

Semisynthesis of linarin and acacetin from the Citrus flavonoid diosmin was performed via, as first intermediate, the 3'-O-phenyltetrazolyl ether of diosmin. This paper relates also a semisynthetic access to 6-iodoapigenin derivatives, which are key compounds in the synthesis of some biflavonoids such as robustaflavone.

Comparison of the absorption of micronized (Daflon 500 mg) and nonmicronized 14C-diosmin tablets after oral administration to healthy volunteers by accelerator mass spectrometry and liquid scintillation counting

Daflon 500 mg, is a micronized purified flavonoid fraction, containing 90% w/w diosmin and 10% w/w of flavonoids expressed as hesperidin, used clinically in the treatment of chronic venous insufficiency and hemorrhoidal disease. This study was designed to investigate the influence of particle size on the overall absorption of diosmin after oral administration of micronized (mean particle size = 1.79 microm, with 80% of particles having a size lower than 3.45 microm) and nonmicronized diosmin (mean particle size = 36.5 microm, with 80% of particles comprised between 19.9 and 159 microm). In a double blinded, cross-over study design, 500 mg tablets containing trace amounts (approximately 25 nCi) of (14)C-diosmin were administered to 12 healthy male volunteers as a single oral dose. Accelerator mass spectrometry and liquid scintillation counting were used for the measurement of (14)C-diosmin in urine and feces. Absorption of (14)C-diosmin from the gastrointestinal tract, measured by the urinary excretion of total radioactivity, was significantly improved with the micronized (57.9 +/- 20.2%) compared with the nonmicronized material (32.7 +/- 18.8%). Statistical comparison of the urinary excretion of the two pharmaceutical formulations showed this difference to be highly significant (p = 0.0004, analysis of variance). The overall excretion of the radiolabeled dose was 100% with mean +/- SD of 109 +/- 23% and 113 +/- 20% for the micronized and nonmicronized forms, respectively. The results of this study show: 1. the impact of a reduction of particle size on the extent of absorption of diosmin, giving a pharmacokinetic explanation to the better clinical efficacy observed with the micronized formulation, and 2. the use of accelerator mass spectrometry in conjunction with liquid scintillation counting in measurement of bioavailability in a human cross-over study comparing two drug formulations containing trace amounts of radioactivity.

[Activity of purified diosmin in the treatment of hemorrhoids]

Several theories on the etio-pathogenesis and physio-pathology of hemorrhoids have been up to now proposed. From the fisio-pathological viewpoint, particular importance is retained by the vascular factor, which in its turn is influenced by mechanical and sphinceric factors, that impair the venous back-flow. In the evidence of an hemorrhoidal crisis, characterized by local oedema, pain and bleeding, the use of bioflavonoid drugs is deemed to be the first choice. We investigated the use of purified diosmin, given at a dose of two 450 mg tablets bid for the first 7 days, then at 1 tablet bid for up to 2 months, in a group of 66 patients suffering from primitive hemorrhoids of grade 1-4. Our results confirmed diosmin efficacy in decreasing both pain and bleeding: reduction rates of 79% and 67%, respectively, were reached in the first treatment week. In the second week, figures were 98% and 86%, respectively. Diosmin tolerability was excellent: this characteristic makes the drug very easy to handle by the general practitioner and also useful to the proctologist in the preparation of patient to further treatments.