In Vitroantidiabetes and Antihypertension Properties of Phenolic Extracts From Bitter Leaf (Vernonia Amygdalinadel.)

Bitter leaf is a popular vegetable commonly consumed and which has been employed in traditional medicine for the prevention/management of diabetes and hypertension for centuries in the tropical Africa. However, possible mechanism underlining its hypoglycemic and antihypertension is not clear. Therefore, this study sought to investigate the inhibitory effect of free and bound phenol extracts of bitter leaf on key enzymes linked to type-2 diabetes (α-glucosidase and α-amylase) and hypertension (angiotensin-I converting enzyme [ACE]). The free and bound phenol extracts significantly (P < 0.05) inhibited α-amylase and α-glucosidase activities in vitro in a dose-dependent pattern (4–16 µg/mL). However, the α-glucosidase inhibitory activity of the extracts were significantly (P < 0.05) higher than their α-amylase inhibitory activity. Furthermore, the ACE inhibitory activity of the extracts also followed a dose-dependent pattern (5–20 µg/mL), and the bound phenol extract significantly (P < 0.05) inhibited ACE more than the free phenol extract. However, there exists a strong correlation between the enzyme inhibitory activities and the phenol content of the extracts. Therefore, the inhibition of α-amylase, α-glucosidase and ACE, coupled with the antioxidant activities of bitter leaf phenolic-rich extracts, could be a possible mechanism through which Vernonia amygdalina exert its antidiabetes and antihypertension properties. PRACTICAL APPLICATION This manuscript deals with the possibilities of using phenolic extracts of bitter leaf as a nutraceutical source for the management of diabetes and hypertension.