Folate content of cultivated and wild traditional leafy vegetables found in Nigeria

Abstract

Folate is an important micronutrient in the prevention of neural tube defects and cardiovascular disease. Given its importance, it is necessary to establish accurately the folate content of food that could contribute significantly to dietary intake. The aim of the study was to quantify the folate content in raw and cooked traditional leafy and non‐leafy vegetables because there is a dearth of information on the folate content leafy vegetables found in Nigeria. The vegetables included: Corchorus olitorius, Adansonia digitata, Abelmoscus esculentus (fruit), Abelmoscus esculentus (leaves), Amaranthus hybridus, Launaea taraxacifolia, Solanum macrocarpon, and Crassocephalum crepidioides. They were further cooked in boiling water, until assessed as cooked according to Nigerian eating habits.Folate is found in foods mainly as polyglutamate. The analysis of folate in the raw and cooked vegetable samples followed the process of extraction, deconjugation (using chicken pancreas deconjugase), derivatisation (a series of chemical reactions to convert all folate present in the deconjugated sample extracts, to 5‐methyltetrahydrofolic acid (THF‐5CH3) monosodium glutamate and / or diglutamate), purification by affinity chromatography with Folate Binding Protein and quantification by HPLC equipped with fluorimetric detection.Folate content in the raw samples ranged from 183.4 μg/100g (FW) in Corchorus olitorius to 21.5 μg/100g (FW) in Solanum macrocarpon leaves; and in the boiled samples from 48.6 μg/100g (FW) in Launaea taraxacifolia to 8.5 μg/100g (FW) in Solanum macrocarpon. Loss of folate in the boiled vegetables varied from 46.6% in Launaea taraxacifolia to 88.4% in Adansonia digitata.Traditional green leafy vegetables are good sources of folate. However cooking of the vegetables caused a considerable decrease in the folate content of the vegetables. Considering that most leafy vegetables are consumed in their cooked form in Nigeria, preparation methods of traditional leafy vegetables that would allow for optimal retention of folate are necessary.Support or Funding InformationThis work was supported by an Agropolis Foundation grant for the internship of SIE and FWMD at Institut National de la Recherch Agronomique (INRA), Avignon, France. AWARD Fellowship provided the platform and opportunity of a 6‐month research attachment/ Advanced science training in INRA to conduct this research; University of Ibadan granted the permission to participate in the Advanced Science training during which this study was carried out. Labex Agro also supported this work. Uncultivated/wild and cultivated traditional green leafy vegetables studied Scientific name Family English name Local/common name Status Amaranthus hybridus L. Amaranthaceae Pig weed Efo tete/ green Cultivated Abelmoscus manihot (L.) Medikus (leaves and tender shoots) Malvaceae Okro leaves Ilasa Adansonia digitatad Malvaceae Baobab leaves Luru / kuka Uncultivated Corchorus olitorius L. Malvaceae Jute mallow Ewedu Cultivated Crassocephalum crepidioides (Benth.) S. Moore Asteraceae Ebolo Uncultivated Launaea taraxacifolia (Wild.) Amin, ex C. Jeffrey Asteraceae African lettuce/wild lettuce Yanrin Uncultivated Solanum macrocarpon L. Solanaceae Efo igbagba Cultivated/wild Folate content of vegetables: RESULTS – Folate content of traditional green leafy vegetables Vegetable Condition Moisture Folic acid Loss Local/common name Scientific name % μg/100g % Ewedu Corchorus olitorius Fresh 82.59 183.36±12.9 74.2 Boiled 95.13 47.31 ±3.7 Luru / kuka Adansonia digitata Dried ‐ 149.64±13.9 88.4 Boiled 90.11 17.36±2.1 Okro/ ila Abelmoscus esculentus fruit Fresh 87.09 106.00±15.6 66.3 Boiled 95.77 35.69±8.49 Ilasa Abelmoscus manihot Fresh 77.05 46.75±9.49 n/a Efo tete/ green Amaranthus hybridus Fresh 84.34 62.15±13.7 48.2 Boiled 91.58 32.19±4.9 Yanrin Launaea taraxacifolia Fresh 88.12 91.13±11.2 46.6 Boiled 92.16 48.63±8.4 Efo igbagba Solanum macrocarpon Fresh 84.82 21.54±3.1 60.6 Boiled 89.55 8.48±1.2 Ebolo Crassocephalum crepidioides Fresh 89.07 70.98±4.9 75.8 Boiled 94.1 17.18±1.7