Nutritional value, micronutrient and antioxidant capacity of some green leafy vegetables commonly used by southern coastal people of Bangladesh

S.M Neamul Kabir Zihad,Yashu Gupt,Shaikh J Uddin,Muhammad Torequl Islam,Md Rabiul Alam,Shahin Aziz,Mahmood Hossain,Jamil A Shilpi,Lutfun Nahar,Satyajit D Sarker

doi:10.1016/j.heliyon.2019.e02768

Abstract

Southern coastal people of Bangladesh are highly vulnerable to food insecurity and malnutrition due to coastal flooding, deforestation and increased soil salinity. A number of green leafy vegetables are found in the southern coastal belt being traditionally eaten as daily basis by local people. But they are unaware of nutritional and medicinal use of these vegetables. To contribute to their wider utilization, five common vegetables namely Hibiscus sabdariffa, Trianthema portulacastrum, Diplazium esculentum, Heliotropium indicum L. and Hygrophila auriculata were selected for analysis of nutritional proximate, micronutrients and antioxidant potential. Nutritional properties were analyzed in terms of moisture, pH, protein, lipid, ash, fibre, minerals and carbohydrate. Total flavonoid, tannin and antioxidant capacity were evaluated using established protocols. The results demonstrated that collected plants are rich in carbohydrate, fibre, proteins, moisture and ash content but low in lipid content. The mineral elements were high with remarkable amount of Na (19.9–21.5 mg/gm), K (7.9–13.5 mg/gm) and P (1.0–1.8 mg/gm). All the samples were found to have considerable amount of flavonoid (90.6–144.5 mg QE/gm) and tannin content (26.8–57.2 mg GAE/gm). The IC50 value of DPPH and superoxide radical scavenging was the lowest for H. indicum (37.1 and 83.4 μg/ml, respectively) whereas T. portulacastrum possessed high reducing power (IC50 53.7 μg/ml). Among the five investigated species, T. portulacastrum and H. indicum were found to have good nutritional and antioxidant properties, thus can be promoted as a significant source of nutritional and antioxidant food supplements.

Highlights

Food security is one of the global problems and exists for decades
The values of 1.9% and 2.16% for H. indicum and D. esculentum were similar to 0.675% and 3.40% reported for African H. indicum and D. esculentum from Philipines [25, 27], whereas the lipid content (5.26%) for H. sabdariffa was higher compared to 1.1 % reported for Indian species of H. sabdariffa [28]
In the present nutritional proximate analysis, the results demonstrated that out of the five coastal species studied, T. portulacastrum recorded as higher amount of ash and fibre content, while D. esculentum and H. sabdariffa recorded as higher amount of protein and carbohydrate content

Summary

Introduction

Food security is one of the global problems and exists for decades. Lack of minerals, vitamins and other nutritional elements can cause depletion of respective antioxidant enzymes level which led to oxidative stress [1]. Antioxidant supplements or antioxidant-containing foods play an important role in protection of oxidative damage when endogenous mechanism of antioxidant protection becomes unbalanced. Protein hydrolyzates and some amino acids, present in different food, were found to have antioxidant properties because of their free radical scavenging ability [4]. The most commonly used synthetic antioxidants at the present time (such as butylated hydroxyanisole (BHA), butylhydroxytoluene (BHT), propyl gallate and tert-butylhydroxyquinone) have restricted use in foods as they are suspected to be carcinogenic and to cause liver damage. Around the world there is currently great interest in studying the dietary supplements (in foods) containing natural antioxidants that can protect the human body from free radicals and retard the progress of many chronic diseases [3, 5]

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Conclusion