R. O. Macêdo

Plants and chemical constituents with giardicidal activity

Intestinal infection caused by Giardia lamblia represents a serious public health problem, with increased rates of prevalence in numerous countries. Increased resistance of the parasite and the side-effects of the reference drugs employed in the treatment of giardiasis make necessary to seek new therapeutic agents. Natural products, especially of plant origin, represent excellent starting point for research. The objective of this study is to review the literature on plant extracts, fractions and chemical constituents whose giardicidal activity has been investigated in vitro. The review describes 153 (one hundred and fifty-three) plant species from 69 (sixty-nine) families that were evaluated for their giardicidal activity. The geographical distribution of the plant species, the part used, preparation, strain of Giardia lamblia tested and the results obtained by the authors are also given. One hundred and one compounds isolated from plant species, classified by chemical class, are presented. Recent aspects of research on natural products of plant origin employed in the treatment of giardiasis are also discussed.

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.

Anxiolytic-like activity and GC–MS analysis of (R)-(+)-limonene fragrance, a natural compound found in foods and plants

The traditional use of essential oils in aromatherapy has offered numerous health benefits. However, few scientific studies have been conducted with these oils to confirm their therapeutic efficacy. (+)-Limonene is a chemical constituent of various bioactive essential oils. The present study reports on the anxiolytic-like effects of (+)-limonene in an elevated maze model of anxiety in mice. At concentrations of 0.5% and 1.0%, (+)-limonene, administered to mice by inhalation, significantly modified all the parameters evaluated in the elevated plus maze test. The pharmacological effect of inhaled (+)-limonene (1%) was not blocked by flumazenil. Analysis of (+)-limonene using gas chromatography-mass spectrometry (GC-MS) showed its volatility to be high. These data suggest possible connections between the volatility of (+)-limonene and its anxiolytic-like effect on the parameters evaluated in the elevated plus maze test. The data indicate that (+)-limonene could be used in aromatherapy as an antianxiety agent.

Application of Thermal Analysis in The Characterization of Anti-hypertensive Drugs

The present work reports studies of the thermal behaviour of some anti-hypertensive drugs. Their purities were determined by DSC and specialized pharmacopeial methods. The activation energy values suggest the following sequence of satability: nifedipine>propanolol hydrochloride>captoril. Analysis of the DSC data indicated that the degrees of purity of nifedipine, captopril and propanolol hydrochloride were similar to those found by pharmacopeial methods BP 93 and USP 23. The simplicity, speed and low operational costs of thermal analysis justify its application in the quality control of pharmaceutical drugs.

Compatibility and Stability Studies of Propranolol Hydrochloride Binary Mixtures and Tablets for TG and DSC-photovisual

This study demonstrates the thermalanalysis applications in compatibility and stability studies of the propranolol binary mixture sand tablets A and B. The propranolol binary mixtures were prepared in the laboratory and compared to the fully formulated tablets using the thermogravimetric (TG) and calorimetric(DSC) methods. DSC of binary mixtures showed similar phase transition to propranolol drug. The tablets phase transition decreased and there was no detectable significant interaction in propranolol–lactose mixture and tablets. The DSC-photovisual test revealed an interaction similar to the Maillard reaction. The TG isothermal study showed a difference in the profile between the drug and tablets due excipients quality and problems in manufacture process. The kinetic parameters indicated a lower stability for the tablets than propranolol drug. The thermal techniques thermally differentiated the propranolol preparations demonstrating the importance in the design development of pharmaceuticals solid-dosage form.

Studies of cimetidine pre-formulated and tablets for TG and DSC coupled to the photovisual system

Abstract This work studied the compatibility pre-formulated drug–excipient mixtures and tablets of cimetidine by TG and DSC coupled to a photovisualization system. The excipients PVPK30, explocel, microcel MC101, aerosil, and magnesium stearate were studied. Curves for the phase transitions of pre-formulated, microcel– and explocel–cimetidine were obtained. The results showed that the excipients, microcel and explocel, did not produce changes in the thermal behavior of cimetidine. This fact was confirmed by the DSC coupled photovisualization system. The rate constants for the thermal decomposition reaction were determined by an isothermal thermogravimetric (TG) method using the classical Arrhenius equations. The results showed that cimetidine tablets presented a stability higher than the cimetidine–excipient mixtures.

Thermal stability of metronidazole drug and tablets

TG and DSC data were used to determine the thermal parameters of metronidazole drug and tablets. Three tablets A, B and C were analysed. The TG curves of metronidazole drug and tablets A and B displayed five and C four thermal decomposition processes, respectively. Analysis of the DSC data pointed to chemical interactions between metronidazole drug and the excipients of tablets, suggested by alterations in the melting point of metronidazole. The rate constants obtained from the isothermal TG data presents following sequence of the thermal stability: tablet A>tablet C>metronidazole drug>tablet B.

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.

Application of thermogravimetry in the quality control of mebendazole

A study was made of the thermal behavior of the starting materials, their mixtures and the resulting mebendazole tablets. The thermal curves were obtained with a Shimadzu thermobalance, model TGA-50, using an air flow of 50 mL min−1 and a heating rate of 10°C min−1 in the temperature interval 30–900°C. The reaction constant velocities for the mebendazole salt and tablets were determined isothermally, using the Arrhenius expression. The thermal stability of mebendazole tablets is lower than that of the mebendazole salt, due to the presence of starch and lactose in the composition. Analysis of the data reveals that thermogravimetry is a powerful tool in pharmaceutical technology and quality control.

Action of silver nanoparticles towards biological systems: cytotoxicity evaluation using hen's egg test and inhibition of Streptococcus mutans biofilm formation

This study aimed to evaluate the cytotoxicity and bactericidal properties of four silver nanoparticle (AgNP) colloids and their ability to inhibit Streptococcus mutans biofilm formation on dental enamel. The cytotoxicity of AgNPs was evaluated based on signs of vascular change on the chorioallantoic membrane using the hens egg test (HET-CAM). Bactericidal properties and inhibition of S. mutans biofilm formation were determined using a parallel-flow cell system and a dichromatic fluorescent stain. The percentage of viable cells was calculated from regression data generated from a viability standard. AgNP colloids proved to be non-irritating, as they were unable to promote vasoconstriction, haemorrhage or coagulation. AgNP colloids inhibited S. mutans biofilm formation on dental enamel, and cell viability measured by fluorescence was 0% for samples S1, S2, S3 and S4 and 36.5% for the positive control (diluted 30% silver diamine fluoride). AgNPs are new products with a low production cost because they have a lower concentration of silver, with low toxicity and an effective bactericidal effect against a cariogenic oral bacterium. Moreover, they do not promote colour change in dental enamel, which is an aesthetic advantage compared with traditional silver products.