Estimation of folate content of cultivated and uncultivated traditional green leafy vegetables in Nigeria

Abstract

The aim of the study was to quantify the folate content of eight samples (seven raw and boiled traditional leafy vegetables and one fruit vegetable). The analysis of folate in the raw and cooked vegetable samples followed the process of extraction, deconjugation using chicken pancreas deconjugase, and derivatization. Through this process, all folate forms in the deconjugated sample extracts were converted to 5-methyltetrahydrofolic acid (THF-5CH 3) monosodium glutamate and/or diglutamate. Purification was done by affinity chromatography with Folate Binding Protein and Reversed-phase high performance liquid chromatography (RP-HPLC) equipped with fluorimetric detection was used to quantify folate. Folate content in the raw samples ranged from 21.5 µg/100 g (FW) in Solanum macrocarpon leaves to 183.4 µg/100 g (FW) in Corchorus olitorius and in the boiled samples values ranged from 8.5 µg/100 g (FW) in S. macrocarpon to 48.6 µg/100 g (FW) in Launaea taraxacifolia leaves. Loss of folate in the boiled vegetables varied from 46.6% in L. taraxacifolia to 88.4% in Adansonia digitata. The difference in folate content of the raw and boiled vegetables were found to be significantly different (p<0.05). Traditional green leafy vegetables studied are good sources of folate in their raw form. However, cooking of the vegetables resulted in considerable decrease of the folate content of the vegetables. Preparation methods of traditional leafy vegetables that will allow for optimal retention of folate are therefore necessary.