The determination of ferulic acid in sugar beet pulp

Abstract

The content of ferulic acid in sugar beet pulp was determined by reverse phase high-pressure liquid chromatography (HPLC) and UV/VIS-spectroscopy. The acid extracts of pectin carrying feruloyl groups were prepared for analysis. To release ferulic acid from pectin the hydrolysis in alkaline medium (pH = 12.5) was performed. Both non-hydrolysed and hydrolysed extracts were measured by UV/VIS-spectroscopy after pH adjustment to the value of 10. The absorbance maximum was observed at 372 nm (ester of ferulic acid) for non-hydrolysed extracts and at 345 nm (sodium ferulate) for hydrolysed extracts. The HPLC estimation of ferulic acid was made in hydrolysed extracts only. The content of ferulic acid in sugar beet pulp was in the range of 0.3-0.9% (m/m). The data obtained by application of the particular methods to one set of samples were statistically compared. The results of all methods were in good agreement with each other.Keywords: ferulic acid; sugar beet pulp; HPLC; UV/VIS-spectroscopy 144 Vol. 19, residues are coupled in the reaction to form a dimer, which is the third way to obtain gel from sugar beet pectins (VO-RAGEN et al. 1994). In addition, ferulic acid and their derivatives have some non-food applications. For example, tocopheryl ferulate and C1-C30 esters of ferulic acid are used in cosmetics and pharmacology due to their antioxidative, antibacterial, anticancerous and antihepatotoxic effects (CROTTY et al. 1998;SCHOENROCK et al. 1997). These compounds are usually prepared by chemical synthesis.The sugar beet pulp is a by-product of sugar industry and raw material for isolation of feruloyl contained sugar beet pectin. The determination of ferulic acid could be important for characterisation of sugar beet pulp as a potential source of this phenolic compound.The aim of this study was the determination of ferulic acid in a set of 24 samples of sugar beet pulp by HPLC and UV/VIS-spectroscopy. METHODS AND MATERIALS Materials:The samples of sugar beet pulp were obtained from various sugar-factories at various harvesting times. The specification of samples is shown in Table 1. The ferulic acid standard (purum 98%) was purchased from Fluka AG, Germany. The common chemicals were bought from Lachema Ltd., Czech Republic.Sample Preparation: Dry sugar beet pulp was ground on a laboratory grinder for 1 minute. 1 g of sample was placed into a flat-bottom flask and 100 ml of 0.2 mol/l HCl were added and kept for 30 min at laboratory temperature. Then the flask was put into a water bath at 85°C for 60 min. The warm suspension was filtrated and the final volume was measured. The pH of some extracts assigned as non-hydrolysed was adjusted by 0.2 mol/l NaOH to the value of 10. The extracts assigned as hydrolysed were prepared by one hour alkali hydrolysis (pH = 12.5) at 25ºC. The hydrolysis was finished by adding 0.2 mol/l HCl to obtain pH = 10. Vol. 19, UV/VIS Spectroscopy: UV/VIS absorption spectra of non-hydrolysed and hydrolysed extracts were measured on double-beam UV 4 Unicam UV/VIS-spectrometer, band width 2 nm. T...

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