A simple method for the estimation of alpha- and beta-carotene in carrots

Carotenoids have diverse biological functions and actions in plants and animals. Carrots are one of the most important sources for dietary intake of vitamin A. The main carotenoids of common carrots are alpha- and beta-carotene. Generally, concentrations of these pigments are quantified by HPLC. However, it is time-consuming and expensive. This report presents a simple method for spectrophotometric estimation of alpha- and beta-carotene in acetone extracts of carrots. Two pigments, alpha-carotene and beta-carotene have similar but different absorption spectra. They have the same absorptivity at 475 nm. Assuming that the acetone extracts of carrots contained only alpha-carotene and beta-carotene, the absorption at given wavelength can be expressed as the sum of each pigment. The availability of each equation was investigated. By regression analysis, the relationship between calculated values and actual values measured by HPLC were examined (n=53). According to the results of statistical analysis, the equations were revised to fit the actual values. The total carotenoid concentration could be expressed as a first-degree equation of absorbance at 475 nm. A high correlation coefficient (r=0.988) was found between calculation and quantification by HPLC. Concentration of beta-carotene was expressed as a first degree polynomial equation of absorbances at 443 and 492 urn (r=0.939). Also alpha-carotene concentration was expressed as an equation of absorbances at 443, 475 and 492 nm (r=0.929).