CAROTENOID COMPOSITION AND CONTENT OF MALAYSIAN VEGETABLES AND FRUITS BY THE AOAC AND HPLC METHODS

The beta-carotene contents of forty vegetables and fourteen fruits were determined using the AOAC open-column (magnesia and Hyflo Super Cel mixture) chromatographic method and compared with a newly developed reverse-phase HPLC method, in which carotenoids were separated isocratically on an octadecylsilane (C18) column using a ternary mixture of acetonitrile, methanol and ethyl acetate. Results obtained showed that the AOAC method gave falsely elevated results for samples containing alpha-carotene, as well as those with very low beta-carotene concentrations. On the other hand, the HPLC method successfully separated and quantitated the major carotenoids present; namely, lutein, cryptoxanthin, lycopene, gamma-and alpha-cartotenes in addition to beta-carotene. The carotenoid composition of most of the green vegetables was rather consistent, comprising only lutein and beta-carotene. In contrast, there was no clear pattern of carotenoids present in the other vegetables and fruits, where several other carotenoids were detected in varying proportions. The vitamin A activity, expressed as mu-g of retinol equivalent (RE), was calculated on the basis of all pro-vitamin A carotenoids (cryptoxanthin, gamma-, alpha- and beta-carotenes) detected. Most of the green leafy vegetables, including several local vegetables, had high RE. Several green non-leafy and other vegetables were found to have low and medium RE. None of the fruits studied may be said to have high vitamin A activity. RE calculated on the basis of results from the AOAC method was found to be erroneously low for samples with significant proportions of pro-vitamin A carotenoids other than beta-carotene, and falsely elevated for those with alpha-carotene. Total carotenoid concentrations can be estimated by taking absorbance readings of sample extracts directly in a spectrophotometer or by the HPLC method. The study clearly shows that the HPLC method would give a more complete picture of the carotenoid composition as well as a more accurate quantitation of the vitamin A value of the vegetables and fruits. The nutritional significane of the findings is obvious since these foods are important sources of vitamin A for the majority of the communities in the country.