Comparing the nutritional, phytochemical, and anti-microbial potential of wild and cultivated Tetragonia decumbens mill.: a promising leafy vegetable for bio-saline agriculture in South Africa

Abstract

Tetragonia decumbens is a neglected edible halophyte that grows naturally in coastal areas of South Africa. Its underutilisation is due to the limited literature on its nutraceutical potential. So, this research was designed to assess the nutritional value, secondary metabolites, and anti-microbial potential of wild and greenhouse cultivated T. decumbens to further support its consumption and potential medicinal use. Samples of T. decumbens were collected from three coastal areas (Strand beach, Muizenberg beach and Blouberg beach) during the dry and wet seasons in Cape Town, and the greenhouse cultivated were subjected to varying salinity doses (0, 50, 100, 150, 200 and 250 mM). Results revealed a considerable increase in minerals (N, P and Mg) and proximate composition (Ash, moisture, and carbohydrates) in greenhouse cultivated plants subjected to 50 mM of salinity while the highest crude fat and neutral detergent fibre were recorded in wild samples. Moreover, heavy metal accumulation (Zn and Fe), phytochemicals, anti-nutrients and anti-microbial activities were more pronounced in wild plants than in cultivated samples. Wild plants collected at Blouberg beach had more heavy metals, anti-nutrients, phytochemicals, and anti-microbial activity. These findings validate for the first time, the relevance of nutritional quality of T. decumbens in assessing its suitability as a source of nutrients and antioxidants with possible medicinal value as shown by the inhibition of harmful bacteria and fungal strains.