Ticiano Gomes do Nascimento

Thermal characterization of the quercetin and rutin flavonoids

Abstract The objective of the present work was to characterize rutin and quercetin by thermogravimetric (TG) and DSC coupled to a photovisual system. The kinetic parameters, rate constant ( k ), activation energy ( E ) and reaction order ( n ) were determined by isothermal and dynamic TG measurements. The results from the TG curves showed the decomposition of the two substances occurring in four stages. The DSC data reveal the presence of several phase transitions for the two compounds. The DSC–photovisual method confirmed the decomposition and polymorphic process for the quercetin and rutin, respectively, according to the literature.

Quality control of thiabendazole pre-formulation and tablets by TG and DSC coupled to the photovisual system

Abstract A stability study and thermal behavior of thiabendazole pre-formulation and tablets were investigated by TG and DSC coupled to a photovisual system. The results showed that the excipients, namely starch, PVP and magnesium stearate did not cause significant chemical interactions with the drug thiabendazole. The rate constants for the thermal decomposition reaction were determined by both an isothermal thermogravimetry and oven accelerated decomposition methods using the classical Arrhenius’ equations. Thermal stability studies showed that thiabendazole tablets presented lower stability than the drug thiabendazole. The data analysis revealed that the drug thiabendazole undergoes a thermal decomposition reaction at a temperature lower that its melting point. This fact was confirmed by DSC coupled to the photovisual system and FT-IR.

Short-term stability studies of ampicillin and cephalexin in aqueous solution and human plasma: Application of least squares method in Arrhenius equation

A limited number of studies with application of the Arrhenius equation have been reported to drugs and biopharmaceuticals in biological fluids at frozen temperatures. This paper describes stability studies of ampicillin and cephalexin in aqueous solution and human plasma applying the Arrhenius law for determination of adequate temperature and time of storage of these drugs using appropriate statistical analysis. Stability studies of the beta-lactams in human plasma were conducted at temperatures of 20°C, 2°C, -20°C and also during four cycles of freeze-thawing. Chromatographic separation was achieved using a Shimpak C(18) column, acetonitrile as organic modifier and detection at 215nm. LC-UV-MS/MS was used to demonstrate the conversion of ampicillin into two diastereomeric forms of ampicilloic acid. Stability studies demonstrated degradation greater than 10% for ampicillin in human plasma at 20°C, 2°C and -20°C after 15h, 2.7days, 11days and for cephalexin at the same temperatures after 14h, 3.4days and 19days, respectively, and after the fourth cycle of freezing-thawing. The Arrhenius plot showed good prediction for the ideal temperature and time of storage for ampicillin (52days) and cephalexin (151days) at a temperature of -40°C, but statistical analysis (least squares method) must be applied to avoid incorrect extrapolations and estimated values out uncertainty limits.

Correlation of thermal analysis and pyrolysis coupled to GC-MS in the characterization of tacrolimus

In recent years, thermal analysis has assumed major role in the pharmaceutical industry because it can be used to evaluate the stability both in the control of raw materials and the finished product, having employment potential in the development and characterization of new products and assessment processes. Tacrolimus (TCR) is a macrolide lactone with potent immunosuppressive activity. The purpose of this study was to characterize tacrolimus raw material using Thermal analysis and Pyrolysis coupled to Gas chromatography-Mass spectrometry (Pyr-GC-MS). It was analyzed four samples of tacrolimus named TCR A, B, C and D. Thermal analysis experiments was performed in Shimadzu equipment, under nitrogen and synthetic air atmosphere in different heating rate. Pyrolysis analysis was conducted in isothermal conditions of 300°C and 400°C coupled to GC-MS, in which the mass spectrometer was operated in scan mode to detect ions in the range of mass of m/z 25-900. The thermal studies by DSC, DTA and DSC-Photovisual showed desolvation process for all tacrolimus raw materials and TG-dynamical demonstrated two pseudo-polymorphic forms (monohydrate and sesquihydrate) of tacrolimus. It was observed good correlation between the stoichiometric mass losses of the TG-dynamical and identification of product ion in Pyr-GC/MS technique. It was possible to correlate the five pyrolytic product ions with the Ozawa kinetic analysis from the thermal decomposition of TG-dynamical. The thermal studies (DSC, DSC-Photovisual, DTA and TG-dynamical) were applied in the thermal characterization of the raw materials of tacrolimus which showed pseudo-polymorphic forms, which must be monitored by pharmaceutical industry, avoiding future problems in pharmaceutical process, chemical stability and bioavailability of the tacrolimus product.

Chemical and microbiological characterization of tinctures and microcapsules loaded with Brazilian red propolis extract

The aim of this study was to characterize tinctures and microcapsules loaded with an ethanol extract of red propolis through chemical, physicochemical and microbiological assays in order to establish quality control tools for nutraceutical preparations of red propolis. The markers (isoflavonoids, chalcones, pterocarpans, flavones, phenolic acids, terpenes and guttiferones) present in the tinctures A and B were identified and confirmed using LC/ESI/FTMS/Orbitrap. Four compositions (A, B, C and D) were prepared to contain B tincture of the red propolis with some pharmaceutical excipients and submitted to two drying processes, i. e. spray-drying and freeze-drying to obtain microcapsules loaded with the red propolis extract. The tinctures and microcapsules of the red propolis were submitted to the total flavonoid content and antioxidant activity tests. The antibacterial activity and minimum inhibitory concentration (MIC) were tested using Staphylococcus aureus ATCC 25293 and Pseudomonas aeruginosa ATCC 27853 strains. The tinctures and microcapsules presented high flavonoid quantities from 20.50 to 40.79 mg/100 mg of the microcapsules. The antioxidant activity and IC50 were determined for the tinctures A and B (IC50: 6.95 µg/mL and 7.48 µg/mL), the spray-dried microcapsules (IC50: 8.89–15.63 µg/mL) and the freeze-dried microcapsules (IC50: 11.83–23.36 µg/mL). The tinctures and microcapsules were proved to be bioactive against gram-positive and gram-negative bacteria with inhibition halos superior to 10 mm at concentration of 200 µg/mL and MIC values of 135.87–271.74 µg/mL using gram-positive strain and 271.74–543.48 µg/mL using gram-negative strain. The tinctures and microcapsules of the red propolis have a potential application for nutraceutical products.

Estudo do processo de intercalação via solução PVP-bentonita: a avaliação da influência do tempo reacional, da proporção de polímero-argila e da massa molar média

In this paper were produced reactions by solution PVP-bentonite, natural and modified, where we studied the influence of reaction time (15, 30, 45 minutes, 1, 24, 48, 72 hours), polymer-clay ratio (2:1, 1:1, 1:2) and molar mass (PVP K-30, PVP K-90). Techniques such as XRD, FTIR and TGA were used to explain the formation of intercalated nanocomposites and their reaction process.

Phytochemical screening, antioxidant and antibacterial activities of some commercial extract of propolis

This study investigated the chemical composition, flavonoids, phenolic compounds, antioxidant activity and antibacterial activity of commercial propolis extracts produced in the Sergipe and Alagoas States of Brazil as potential bioproducts for the food and pharmaceutical industries. Four samples were analyzed, three brown propolis extracts and one red propolis extract, and were characterized through phytochemical screening, chemical, chromatographic profile and antibacterial activity. Phytochemical analysis detected the presence of triterpenoids and phenolic compound in propolis extracts. Propolis extracts showed total phenolic content between 9 and 15% and total flavonoids >2%. Propolis extracts showed excellent antioxidant activity with inhibition of the Free radical DPPH˙ between 97 and 60%, which confirm the results obtained in total phenolics, total flavonoids content and antibacterial activity. The chromatographic profile showed differences for brown propolis samples and quite different from the red propolis extract, which present flavonoids as isoflavonoids, pterocarpans, chalcones and guttiferones. Commercial propolis extract (propolis extract C and propolis extract D) showed excellent activity for Staphylococcus aureus ATCC 25923 and moderate activity for Pseudomonas aeruginosa ATCC 27853. The chemical characterization of propolis extracts is fundamental in the process of standardization and monitoring of the chemical composition susceptible to geographic and seasonal variation. These results point to new possibilities of use as bio-preservative of processed foods as well as in the development of pharmaceuticals and nutraceuticals products from propolis extract C and D in its formulation actuate on the inhibition of some pathogenic microorganisms strains.

Polymeric nanoparticle systems loaded with red propolis extract: a comparative study of the encapsulating systems, PCL-Pluronic versus Eudragit®E100-Pluronic

The aim of the present study was to compare two nanoparticle composition loaded with Brazilian red propolis extract regarding its physicochemical characteristics and its antioxidant and antileishmanial activities. The red propolis nanoparticles in an aqueous medium and in solid-state presented particle size in a nanometric scale with an apparent size of 100–288 nm for the NEPE and 175–380 nm for the NPPE. ATR-FTIR and thermal analysis revealed an encapsulation of flavonoids from the red propolis extract in polymeric matrices for the multidrug delivery system. UPLC-DAD identified red propolis markers (flavonoids) in EPE, NEPE and NPPE. The efficiency of encapsulation (28.0–55.0% for NEPE and 61.2–81.0% for NPPE) were determined and calculated using UPLC-DAD. DPPH method showed the antioxidant activity of both EPE and nanoparticle compositions of red propolis. These polymeric matrices systems were able to encapsulate flavonoids from red propolis extract with specific characteristics of solubility and polarity. EPE and nanoparticles loaded with red propolis extract in the multi-constituent co-delivery system presented leishmanicidal activity and a good correlation was established between IC50 and efficiency of encapsulation. Red propolis nanoparticles exhibited leishmanicidal activity but NEPE presented a lower leishmanicidal effect in relation to NPPE, which showed similar activity compared to EPE. The nanopolymeric matrices choice should be established in propolis nanoparticle compositions to avoid lack of efficacy of bioproducts. Red propolis nanoparticles were shown to be a potential final bulk product for the preparation of various pharmaceutical and cosmetics compositions in therapy against diseases such as leishmaniasis. Scanning Electron Microscopy of red propolis nanoparticles (NEPE 30) (A). ATR-FTIR spectra of NPPE 30 and NPPE placebo (B). Chromatogram of the NPPE 30 (C). Determination of IC using leishmanicidal assay against Leishmania braziliensis for EPE, NEPE and NPPE (D).

Lipase Activity in the Larval Midgut of Rhynchophorus palmarum: Biochemical Characterization and the Effects of Reducing Agents

Lipases have key roles in insect lipid acquisition, storage, and mobilization and are also fundamental to many physiological processes in insects. Lipids are an important component of insect diets, where they are hydrolyzed in the midgut lumen, absorbed, and used for the synthesis of complex lipids. The South American palm weevil Rhynchophorus palmarum is one of the most important pests on commercial palm plantations. However, there are few studies about lipid digestion for this insect. In this work, we have described the biochemical characterization of the lipase activity in the posterior midgut of the R. palmarum palm weevil. Lipase activity was highest between the temperatures of 37 °C and 45 °C and at pH 6.5. Lipase activity was also sensitive to variations in salt and calcium concentrations. Lipases have been described structurally as enzymes with the Ser-His-Asp Catalytic Triad, containing an active serine. The serine protease inhibitor PMSF (phenylmethane sulfonyl fluoride) inhibited the lipases from R. palmarum, demonstrating the importance of a serine residue for this activity. The ability of the lipases to hydrolyze p-Nitrophenyl esters with different chain lengths has revealed the activities of a broad range of substrates. The lipase activities of R. palmarum increased in the presence of reduced glutathione (GSH) and dithiothreitol (DTT), while in the presence of oxidized glutathione (GSSG), activities were drastically reduced. To our knowledge, this study has provided the first information about lipase activity in the R. palmarum palm weevil.