Quantitative Determination of Total Carbohydrates (Recalculated for Fructose After Conversion to Furans) in Burdock Juice

Resumo

Conversion of sugars into furans in acidic solution was used to quantify the carbohydrate contents in plant medicines using juice from fresh greater burdock (Arctium lappa L.) leaves as an example. Hexoses (fructose, glucose) and inulin degraded in acidic solution to form 5-hydroxymethylfurfurol (HMF) and other compounds. Fructose and sucrose could be quantified by spectrophotometry and HPLC and could also be determined spectrophotometrically after UV degradation by using the formation by acid hydrolysis of HMF and its derivatives with chromophores at 283 – 285 nm. It was found experimentally that furan derivatives (HMF) with absorption maximum at 283 nm, which was taken as the analytical wavelength, were formed via acid degradation of the juice and a solution of fructose. The carbohydrate contents in the test samples varied from 1.05 to 1.36%. The relative error of the mean of the result from the proposed method was 7.5%.