Antioxidant activity of hot water extract from the fruit of the Doum palm, Hyphaene thebaica

A hot water extract from the fruit of Hyphaene thebaica was examined for its (i) hydrogen donating activity, (ii) Fe2+-chelating activity, (iii) hydroxyl radical-scavenging activity, (iv) inhibition of substrate site-specific hydroxyl radical formation, (v) superoxide radical-scavenging activity, and (vi) reducing power. The total phenolic content of the fruit extract was also determined in order to quantitate antioxidant activity as gallic acid equivalent (GAE) per ml reaction. The total phenolic content of the Doum fruit is low, but the extract exhibited potent antioxidant activity in terms of GAE. The activities expressed as mmol pure compound equivalent per g GAE content of extract are: (i) 2.85 mmol ascorbic acid equivalent, (ii) 1.78 mmol ethylenediamine tetraacetic acid equivalent, (iii) 192 mmol gallic acid equivalent, (iv) 3.36 mmol gallic acid equivalent, (v) 1.78 mmol gallic acid equivalent and (vi) 3.93 mmol ascorbic acid equivalent. These values were of the same magnitude as antioxidant activity in black tea except for Fe2+-chelating activity which was about 14 times more potent. The results show that the fruit of Hyphaene thebaica’s fruit is a source of potent antioxidants.