Bulé Paiva - Academia.edu (original) (raw)

Papers by Bulé Paiva

Research paper thumbnail of Caffeine and other adulterants in seizures of street cocaine in Brazil

International Journal of Drug Policy, 2003

Cocaine sold as a "street drug" in white powder usually contains several adulterants and diluents... more Cocaine sold as a "street drug" in white powder usually contains several adulterants and diluents. The purpose of this research was to quantify cocaine content and to check the presence of adulterants in illicit samples seized by the Narcotic and Toxic Substances Regional Department of Alfenas and Varginha districts, Brazil, in the year 2001. The identification of cocaine and adulterants in 209 samples, was screened by thin-layer chromatography (TLC) and confirmed/quantified by gas chromatography/flame ionization detector (GC/FID). The pharmacologically inactive adulterants (starch, carbonates/bicarbonates and sugars) were analysed by qualitative tests or TLC. 88.9% of the samples analysed gave positive results for cocaine in concentrations between 4.3 and 87.1% of the powder. Active compounds detected were caffeine (50.2% of the samples, in concentrations ranging from 2.8 to 63.3% of the powder), lidocaine (65% of the samples, concentrations ranging 0.5-92%), and prilocaine (11% of the samples, concentrations ranging 1.4-20.7%). Carbonate/bicarbonate showed positive results in 41.2%, starch in 51.2% and sugars in 9.6% of the samples. The presence of other substances in cocaine street samples is worrying because they could modify or intensify signs and symptoms of the intoxication, acute or fatal, due to drug.

Research paper thumbnail of Microwave-Assisted Derivatization of Bile Acids for Gas Chromatography/Mass Spectrometry Determination

ISRN Analytical Chemistry, 2013

Bile acids derived from cholesterol are produced in the liver, and their analysis is difficult du... more Bile acids derived from cholesterol are produced in the liver, and their analysis is difficult due to their complex natures and their low concentrations in biological fluids. Mixtures of various derivatives, created via conventional heating, are used for such analyses. Microwave radiation is proposed to accelerate the derivatization process. This paper presents a mass fragmentation study and microwave-assisted derivatization (MAD) for the silylation of bile acids (cholic and ursodesoxycholic) prior to gas chromatography and mass spectrometry analysis. The derivatization was performed using the two-step process of methoximation and silylation. The reaction time, power, and quantity of N,O-bis-(trimethylsilyl) trifluoroacetamide (BSTFA) + 1% trimethylchlorosilane (TCMS) were optimized to improve the derivatization. The optimized derivatization conditions required 210 W for 3 min. The MAD method exhibited linearity with respect to cholic acid between 0.78 and 20.0 μg mL−1 with an LOQ o...

Research paper thumbnail of New method for the determination of bile acids in human plasma by liquid-phase microextraction using liquid chromatography-ion-trap-time-of-flight mass spectrometry

Journal of Chromatography A, 2015

Please cite this article in press as: M.J.N. de Paiva, et al., New method for the determination o... more Please cite this article in press as: M.J.N. de Paiva, et al., New method for the determination of bile acids in human plasma by liquid-phase microextraction using liquid chromatography-ion-trap-time-of-flight mass spectrometry,

Research paper thumbnail of Acetylcholinesterase inhibition starting from extracts of Bauhinia variegata L., Bauhinia var. candida (Aiton) Buch.-Ham., and Bauhinia ungulata L

Revista da Sociedade Brasileira de Medicina Tropical, 2011

INTRODUCTION: A treatment to the Alzheimer's disease consists inhibition of the acetylcholine... more INTRODUCTION: A treatment to the Alzheimer's disease consists inhibition of the acetylcholinesterase, which is responsible for the acetylcholine control in the synapses. METHODS: We have investigated the potential of inhibition of the acetylcholinesterase produced by hexane extracts of leaves, branches, and flowers from three Bauhinia specimens, which is based on the technique of thin layer chromatography and on identifying the organ of the plant that possesses larger concentration of inhibitors. RESULTS: Retention factor analysis shows values of 0.31aA, 0.31aA, and 0.46aB for flowers B. variegata, B. var. candida, and B. ungulata, respectively. CONCLUSIONS: The flower extract of B. ungulata is the most suitable for further studies on this inhibition.

Research paper thumbnail of Sampling and analysis of metabolomes in biological fluids

The Analyst, 2014

Metabolome analysis involves the study of small molecules that are involved in the metabolic resp... more Metabolome analysis involves the study of small molecules that are involved in the metabolic responses that occur through patho-physiological changes caused by genetic stimuli or chemical agents.

Research paper thumbnail of Caffeine and other adulterants in seizures of street cocaine in Brazil

International Journal of Drug Policy, 2003

Cocaine sold as a "street drug" in white powder usually contains several adulterants and diluents... more Cocaine sold as a "street drug" in white powder usually contains several adulterants and diluents. The purpose of this research was to quantify cocaine content and to check the presence of adulterants in illicit samples seized by the Narcotic and Toxic Substances Regional Department of Alfenas and Varginha districts, Brazil, in the year 2001. The identification of cocaine and adulterants in 209 samples, was screened by thin-layer chromatography (TLC) and confirmed/quantified by gas chromatography/flame ionization detector (GC/FID). The pharmacologically inactive adulterants (starch, carbonates/bicarbonates and sugars) were analysed by qualitative tests or TLC. 88.9% of the samples analysed gave positive results for cocaine in concentrations between 4.3 and 87.1% of the powder. Active compounds detected were caffeine (50.2% of the samples, in concentrations ranging from 2.8 to 63.3% of the powder), lidocaine (65% of the samples, concentrations ranging 0.5-92%), and prilocaine (11% of the samples, concentrations ranging 1.4-20.7%). Carbonate/bicarbonate showed positive results in 41.2%, starch in 51.2% and sugars in 9.6% of the samples. The presence of other substances in cocaine street samples is worrying because they could modify or intensify signs and symptoms of the intoxication, acute or fatal, due to drug.

Research paper thumbnail of Microwave-Assisted Derivatization of Bile Acids for Gas Chromatography/Mass Spectrometry Determination

ISRN Analytical Chemistry, 2013

Bile acids derived from cholesterol are produced in the liver, and their analysis is difficult du... more Bile acids derived from cholesterol are produced in the liver, and their analysis is difficult due to their complex natures and their low concentrations in biological fluids. Mixtures of various derivatives, created via conventional heating, are used for such analyses. Microwave radiation is proposed to accelerate the derivatization process. This paper presents a mass fragmentation study and microwave-assisted derivatization (MAD) for the silylation of bile acids (cholic and ursodesoxycholic) prior to gas chromatography and mass spectrometry analysis. The derivatization was performed using the two-step process of methoximation and silylation. The reaction time, power, and quantity of N,O-bis-(trimethylsilyl) trifluoroacetamide (BSTFA) + 1% trimethylchlorosilane (TCMS) were optimized to improve the derivatization. The optimized derivatization conditions required 210 W for 3 min. The MAD method exhibited linearity with respect to cholic acid between 0.78 and 20.0 μg mL−1 with an LOQ o...

Research paper thumbnail of New method for the determination of bile acids in human plasma by liquid-phase microextraction using liquid chromatography-ion-trap-time-of-flight mass spectrometry

Journal of Chromatography A, 2015

Please cite this article in press as: M.J.N. de Paiva, et al., New method for the determination o... more Please cite this article in press as: M.J.N. de Paiva, et al., New method for the determination of bile acids in human plasma by liquid-phase microextraction using liquid chromatography-ion-trap-time-of-flight mass spectrometry,

Research paper thumbnail of Acetylcholinesterase inhibition starting from extracts of Bauhinia variegata L., Bauhinia var. candida (Aiton) Buch.-Ham., and Bauhinia ungulata L

Revista da Sociedade Brasileira de Medicina Tropical, 2011

INTRODUCTION: A treatment to the Alzheimer's disease consists inhibition of the acetylcholine... more INTRODUCTION: A treatment to the Alzheimer's disease consists inhibition of the acetylcholinesterase, which is responsible for the acetylcholine control in the synapses. METHODS: We have investigated the potential of inhibition of the acetylcholinesterase produced by hexane extracts of leaves, branches, and flowers from three Bauhinia specimens, which is based on the technique of thin layer chromatography and on identifying the organ of the plant that possesses larger concentration of inhibitors. RESULTS: Retention factor analysis shows values of 0.31aA, 0.31aA, and 0.46aB for flowers B. variegata, B. var. candida, and B. ungulata, respectively. CONCLUSIONS: The flower extract of B. ungulata is the most suitable for further studies on this inhibition.

Research paper thumbnail of Sampling and analysis of metabolomes in biological fluids

The Analyst, 2014

Metabolome analysis involves the study of small molecules that are involved in the metabolic resp... more Metabolome analysis involves the study of small molecules that are involved in the metabolic responses that occur through patho-physiological changes caused by genetic stimuli or chemical agents.