In vitro and in vivo anti-hyperglycemic effects of green and red mustard leaves (Brassica juncea var. integrifolia)

Brassica juncea var. integrifolia, known as mustard leaf, is used as a medicinal plant in Asia, however, knowledge for their health benefits is limited. Here, we evaluate the total phenolic contents, phenolic profile, and antioxidant activity of green and red mustard leaves (EG and ER, respectively). Additionally, the inhibitory activity of EG and ER against rat intestinal α‐glucosidase and porcine‐pancreatic α‐amylase were investigated. The total phenolic contents of EG and ER were 1,228.48 ± 36.81 and 850.75 ± 28.88mg/100 g, respectively. The total phenolic contents correlated to the observed antioxidant activities. ER had significant α‐glucosidase but low α‐amylase inhibitory activity. Using an Sprague‐Dawley‐Rat model, ER appeared to have better glucose‐lowering effect when compared to EG, after a sucrose‐loading test. This is the first report evaluating mustard leaves for potential glucose‐lowering effects. Our observations suggest that ER has better potential for this bioactivity and this observation possibly correlates with the sinigrin contents observed in both extracts. PRACTICAL APPLICATIONS: Mustard seeds are widely used for the production of food products and have been evaluated for their health benefits. Currently, mustard leaves are considered a low‐value by‐product of the mustard plant and are significantly underutilized. To support the sustainable utilization of mustard plant, it is important to initiate the utilization of mustard leaves. Value addition in mustard leaves through research efforts that define possible health benefits of this resource will significantly assist toward the possible utilization of this low‐value, underutilized raw material to produce high‐value, health beneficial, food ingredients.