Abstract
Popular Nigerian vegetables namely, cabbage, spinach, bitter leaf, water leaf, ewedu, roselle and lettuce obtained from Sokoto metropolis, Nigeria were analysed for nitrate contents by ultra-violet (UV)-spectrophotometric method. The fresh leaves of the samples were chopped and ground using mortar and pestle for the analysis. Absorbance of each sample was obtained in three replicate and the calibration graph of standards nitrate were used in determining the concentration of each sample. Cabbage, spinach, ugwu and lettuce contain the lowest amount of nitrate in this study (0.109 ± 0.035 µgml-1, 1.530 ± 0.130 µgml-1, 1.730 ± 0.328 µgml-1 and 2.185 ± 0.157 µgml-1) in comparison with the nitrate contents of samples like roselle, ewedu, water leaf and bitter leaf which contain the highest amount (2.938 ± 0.060 µgml-1, 3.682 ± 0.140 µgml-1, 3.924 ± 0.160 µgml-1 and 4.351 ± 0.190 µgml-1). These values fall within those recommended for nutritional purpose. Key words: Nitrate contents, vegetables, Sokoto, absorbance.
Highlights
A number of ailments have their origin in our diet, either directly or indirectly
Green vegetables are a major source of dietary nitrate intake
Namely: spinach, lettuce, water leaf, bitter leaf, ugwu, ewedu, roselle and cabbage were purchased from Sokoto fish, meat and vegetable market
Summary
A number of ailments have their origin in our diet, either directly or indirectly. Many modern diseases are as a result of nutritional deficiencies. Green vegetables are a major source of dietary nitrate intake. Nitrate is a naturally occurring compound that is part of nitrogen cycle, as well as approved food in which they play an important role in the nutrition and function of plants. Nitrates are important components of vegetables, they occur widely in our drinks and food (Okafor and Ogbonna, 2003; EFSA, 2008). Nitrates are nitrogen-oxygen chemical units which combine with various organic and inorganic compounds (Croitoru, 2012). Crop containing high level of nitrates can be identified by laboratory test. Nitrates in vegetables and fruits have no taste or smell (FFTC, 2007). Nitrates occur naturally in fruits and vegetables, but only in small quantities, they can rise to high levels in intensively grown crops (Croitoru, 2012)
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