Comparative study of two spectrophotometric reagents for catechol analysis in guaraná seeds powder

Abstract

Neste trabalho são descritos e comparados dois métodos espectrofotométricos para análise de catecol (o-hidroxifenol) em Paullinea cupana var. sorbilis, popularmente conhecido como guaraná. As amostras de sementes trituradas foram extraídas com etanol 97% v/v e as soluções tratadas com p-aminofenol em meio etanólico alcalino ou m-aminofenol e metaperiodato de sódio em solução tampão (pH 3.0). A absorbância foi medida a 586 nm e 520 nm respectivamente. Quatro produtos comerciais diferentes foram analisados e os resultados foram comparados com aqueles obtidos com m-aminofenol. Apesar da boa qualidade das curvas de calibração, nos dois métodos houve interferência da matriz, o que foi contornado usando-se o método da adição de padrão. A comparação entre os resultados obtidos pelos dois métodos, usando o teste estatístico t de Student, mostrou que não há diferenças significantes para um nível de confiança de 95%.In this article are described and compared two spectrophotometric methods for the analysis of catechol (o-hydroxyphenol) in Paullinea cupana var. sorbilis, popularly known as guaraná. The pounded seed samples were extracted with ethanol 97% v/v and the solutions were treated with p-aminophenol in alkaline ethanolic medium or m-aminophenol and sodium metaperiodate in buffered aqueous solution (pH 3.0). The absorbance was measured at 586 nm and 520 nm respectively. Four different commercial products were analyzed and the results were compared with those obtained with the m-aminophenol method. Despite the good quality of the calibration curves, in the two methods the interference of the matrix was observed. This problem was settled using the standard addition method. Comparison between the results obtained by the two methods, using the statistical Student's t-test, showed that there is no significant difference at the 95% confidence level.

Antibacterial and antioxidant activities of ethanol extract from Paullinia cupana Mart.

“…The calibration curve was prepared by loading, separately, in six 10 ml volumetric flasks 3.0 ml of 2% (w/v) NaOH solution, 3.0 ml of p-aminophenol solution and 0.0, 10.0, 25.0, 50.0, 75.0 and 100 l of catechol standard solution. The final volume was completed with ethanol and the absorbance was measured at 586 nm 1 min after adding catechol (Magna et al, 2003). As for catechol determination, we used the standard addition method because of the interference of the matrix.…”

“…Then 1 ml of guarana ethanol extract and the adequate catechol standard solution volume 0.0, 10.0, 25.0, 50.0, 75.0 and 100 l were added. The final volume was completed with ethanol and the absorbance was measured at 586 run 1 min after the addition of catechol (Magna et al, 2003). The quantitative analysis of catechol in guarana seeds was performed by a particular spectrophotometric method (Magna et al, 2003): the reaction of p-aminophenol with catechol forms indophenol dye-like species.…”

Capillary Gas Chromatography-Mass Spectrometry (CGC-MS) Analysis and Antioxidant Activities of Phenolic and Components of Guarana and Derivatives

“…The quantitative analysis of catechol in guarana seeds was performed by a spectrophotometric method [27] based on the reaction of p-aminophenol with catechol giving rise to indophenol dye-like species. For the calibration curve, the paminophenol solution was prepared at 1 mM using 0.1 M HCl aqueous solution.…”

“…The calibration curve was prepared by loading, separately, in six 10 mL volumetric flasks 3.0 mL of 2% (w/v) NaOH solution, 3.0 mL of paminophenol solution and 0.0, 10.0, 25.0, 50.0, 75.0 and 100 μL of catechol standard solution. The final volume was completed with ethanol and the absorbance was measured [27] at 586 nm 1 min after adding catechol. As for catechol determination, we used the standard addition method because of the interference of the matrix.…”

“…Then 1 mL of guarana ethanol extract and the adequate catechol standard solution volume 0.0, 10.0, 25.0, 50.0, 75.0 and 100 μL were added. The final volume was completed with ethanol and the absorbance was measured [27] at 586 nm run 1 min after the addition of catechol.…”