Nora B. Pappano

First and second order derivative spectrophotometric determination of benzyl alcohol and diclofenac in pharmaceutical forms

Abstract Diclofenac sodium is a drug with analgesic, antipyretic and anti-inflammatory properties. It is present in numerous pharmaceutical preparations. In injectable forms, it is usually accompanied by benzyl alcohol as an excipient, which is used as a blocking anesthetic (4%) and an antiseptic (4–10%). In this work spectrophotometric methodology was used in order to determine diclofenac and benzyl alcohol in injectable formulations by applying, on the one hand, the first-derivative method of crossing zero for diclofenac sodium and on the other, second derivative for benzyl alcohol. The results obtained show that this method has a significant advantage over other techniques and it is appropriate for routine pharmaceutical analysis.

Rapid and accurate determination of chlorpheniramine maleate, noscapine hydrochloride and guaiphenesin in binary mixtures by derivative spectrophotometry

Rapid and accurate binary mixture resolution of chlorpheniramine maleate-noscapine hydrochloride and chlorpheniramine maleate-guaiphenesin, was performed. Derivative spectrophotometry, by the zero-crossing measurements, was used due to the drugs closely overlapping absorption spectra. Neither sample pretreatment nor separation were required. Linear calibration graphs of first derivative values at 268.0 and 261.0 nm for chlorpheniramine-maleate-noscapine hydrochloride and at 273.2 and 261.0 nm for chlorpheniramine-guaiphenesin were obtained vs. concentration with negligible intercept on the y-axis. Thus, the derivative spectrophotometry method was applied to the determination of these drugs in binary mixtures obtaining selectivity, accuracy and precision.

Effects of Dimethylformamide and L-Menthol Permeation Enhancers on Transdermal Delivery of Quercetin

In this work a feasibility study of transdermal delivery system for quercertin (Q) in carbopol gel through abdominal hairless pig skin in vitro was performed. Dimethylformamide (DMF) and L-menthol (M) were selected as enhancers. Permeation experiences were carried out by using Franz-type diffusion cells. Phosphate saline buffer (pH 7.4) was used in the receptor compartments. All the system was maintained at 32 ± 0.5°C with a circulating water jacket and magnetic stirring (180 rpm). Samples were analysed by UV-VIS spectrophotometer at 255 nm. Flux (Jm) values, permeation (P) and diffusion (D) coefficients were obtained. Results of Q in CG permeation experiences with different percentages of DMF and M showed that 16.7% DMF and 1.95% L-menthol enhancers were the best quantities for the system tested. Enhancer effect can be attributed to direct action on membrane structure by promoting its distension. Therefore, enhancer substitutes for water in pores, improving active principal permeation through pig skin. M significantly increases Q permeation about 17 times higher than control. The results of permeation experiments with M and DMF using the same enhancer concentration (1.42%) conclude that M action is 9 times higher than DMF, approximately, indicating that M is an effective enhancer for a transdermal therapeutic system of Q in CG as vehicle.

Structure-biological activity relationship of synthetic trihydroxilated chalcones

A atividade bacteriostatica de 2x92,4x92,2-trihidroxichalcona, 2x92,4x92,3-trihidroxichalcona e 2x92,4x92,4-trihidroxichalcona, preparadas por condensacao de 2,4-dihidroxiacetofenona e benzaldeido convenientemente substituido, contra Staphylococcus aureus ATCC 25923 foi avaliada pela tecnica de difusao em placas. Importantes halos de inibicao foram observados para os tres compostos. Com o proposito de esclarecer a relacao estrutura-atividade biologica, as concentracoes inibitorias minimas (CIM) frente a S. aureus foram determinadas, empregando o metodo da diluicao em caldo. Os resultados obtidos foram semelhantes a 2x92,4x92-dihidroxichalcona, observando-se a seguinte ordem: CIM 2x92,4x92,3-(OH)3 > CIM 2x92,4x92-(OH)2 > CIM 2x92,4x92,4-(OH)3 > CIM 2x92,4x92,2-(OH). A sequencia obtida mostra que a introducao de um grupo doador de eletrons (OH) no anel aromatico B provoca um aumento da bioatividade, sendo a intensidade dependente da posicao do substituinte -OH.

A comparative photochemical study on the behavior of 3,3'-dihydroxyflavone and its complex with La(III) as generators and quenchers of reactive oxygen species.

A 1:1 complex between 3,3-dihydroxyflavone (DHF) and La(III) (DHF-La(III)) is formed in methanolic solution with the relatively high apparent stability constant value of 2.3×10(6) and a calculated standard entropy change of 88.2 J mol(-1) K(-1), both at 25 °C. The photophysical properties of the complex and the free flavonoid are discussed in comparison to the well known related compound 3-hydroxyflavone. The ligand photogenerates O2((1)Δg) by energy transfer from its excited triplet state ((3)DHF(*)) to dissolved ground state oxygen, with a quantum yield of 0.13. (3)DHF(*) is quenched by La(III) with a rate constant close to the diffusion-controlled value. The respective abilities of the free flavonoid and DHF-La(III) as quenchers of the riboflavin-photogenerated reactive oxygen species singlet molecular oxygen (O2((1)Δg)) and superoxide radical anion (O2(-)) have been investigated. Both individual compounds were photoirradiated with visible light in the presence of the flavin as the only light-absorbing compound. A detailed kinetics and mechanistic study employing polarographic monitoring of oxygen uptake and time resolved detection of O2((1)Δg) phosphorescence indicates that DHF and the complex react with O2((1)Δg) and O2(-) by a non simple mechanism. The former deactivates O2((1)Δg) in a predominant physical fashion, a fact that constitutes a desirable property for antioxidants. It was found that metal chelation greatly enhances the ability of DHF as an overall O2((1)Δg) quencher.

Vitamin B2-sensitized photooxidation of structurally related dihydroxyflavonoids

Abstract A kinetic study of the processes involved in the vitamin B2 (riboflavin, Rf)-sensitized photooxidation of selected flavonoids ( F ) was carried out in methanolic solution. Under aerobic visible-light-irradiation conditions a complex picture of competitive interactions takes place: the singlet and triplet excited states of Rf are quenched by three F , namely 5,7-dihydroxy-3′,4′-dimethoxyflavanone (FNN); 5,7-dihydroxy-4′,6,8-trimethoxyflavone (FLV) and 2′,4′-dihydroxychalcone (CHL). Concomitantly, the species singlet molecular oxygen [O 2 ( 1 Δ g )] and superoxide anion radical (O 2 •− ) are generated and interact with F and with Rf. CHN and FNN are photooxidised, probably by means of O 2 •− , whereas FVN, the poorest quencher of excited triplet Rf, allows the generation of O 2 ( 1 Δ g ), which oxidises the very flavonoid. The photodegradation of the vitamin is delayed due to an electron transfer process to ground state oxygen.

On the antioxidant properties of therapeutic drugs: quenching of singlet molecular oxygen by aminosalicylic acids

Abstract The ability of the widely employed therapeutic drugs 4-aminosalicylic acid and 5-aminosalicylic acid to act as singlet molecular oxygen (O2(1Δg)) scavengers was investigated at pH 7 and pH 12. The isomer 3-aminosalicylic acid was also included in the study for comparative purposes. All three compounds quench photochemically generated O2(1Δg) with rate constants in the range of 107-108 M-1s-1, depending on the experimental conditions. No chemical reaction (oxidation of the aminosalicylic acids) was detected at the neutral pH, whereas at pH 12 both chemical and physical interactions with O2(1Δg) operated. The physical process implies the de-activation of the oxidant species without destruction of the aminosalicylic acid. The quotients between the overall and reactive rate constants for O2(1Δg) quenching at pH 12 (kr/kt ratios), which account for the actual effectiveness of photodegradation, were relatively low (0.22, 0.04, and 0.06 for 3-, 4- and 5-aminosalicylic acids, respectively). This indicates that the drugs, particularly the 4- and 5-amino derivatives, de-activate the excited oxygen species, at both pH values studied, mainly in a physical fashion, preventing its photodegradation and providing an antioxidative protection for possible photo-oxidizable biological targets in the surroundings.

A COMPARATIVE STUDY OF BACTERIOSTATIC ACTIVITY OF SYNTHETIC HYDROXYLATED FLAVONOIDS

Os flavonoides apresentam, entre outras, uma notavel atividade bacteriostatica. Neste trabalho determinaram-se as concentracoes inibitorias minimas de 5,7,4-trihidroxiflavanona (naringenina), 5,7-dihidroxiflavona e 2,4,4-trihidroxichalcona (isoliquitirigenina) frente a Staphylococcus aureus ATCC 25 923 e comparadas com valores obtidos para outras chalconas e flavanonas investigadas previamente. As velocidades especificas de crescimento e as MICs foram avaliadas por um metodo cinetico-turbidimetrico. A sequencia observada MICflavanona(inactiva) >MIC7-hidroxiflavanona (197,6 µgml-1) > MIC5,7,4-trihidroxiflavanona (120 µgml-1) mostrou que a introducao de um grupo doador de eletrons (-OH) provoca um aumento da bioatividade. Por outro lado, MIC5,7,4-trihidroxiflavanona (120 µg ml-1) >>> MIC2,4,4-trihidroxichalcona (29 µg ml-1) e MIC5,7-dihidroxiflavona (105 µg ml-1) >>> MIC2,4-dihidroxichalcona (28,8 µg ml-1) permitiram concluir que a estrutura chalcona e a mais favoravel para a atividade bacteriostatica dentro da familia dos flavonoides.

News analytical reagents for europium(III)

The complexant reactions of 2-hydroxychalcones with europium(III) are studied by the spectrophotometric method. The apparent formation constants are evaluated using a simple graphical linear method. The sequence of these constant values is explained and compared with aluminium(III) complexant reactions.

Complexant efficiency of 2′-hydroxy-4-R-chalcones for Aluminium (III) and substituent's effect

The complexant efficiency with aluminium of 2-hydroxy-4-R-chalcones, which depends on the nature and positions of the substituent was studied by a spectrophotometric method. The apparent formation constant was determined. The quantitative analysis of the substituents influence on the complexation reaction equilibrium was made using the Hammett relation. The constant sigma magnitudes of groups OH, OCH(3), Cl and F in the 4-position agree with values reported in the literature.