In vitro studies on the effect of watercress juice on digestive enzymes relevant to type 2 diabetes and obesity and antioxidant activity

Abstract Inhibition of enzymes involved in carbohydrate and lipids metabolism is an important strategy against type 2 diabetes and obesity, by suppressing dietary sugar and fat absorption. This work reports, for the first time, the in vitro inhibition of α‐glucosidase, α‐amylase and lipase by watercress juice (WJ). Juice was analyzed for qualitative and quantitative composition and in vitro antioxidant activities. Several components were identified, namely hydroxycinnamic acids, flavonols, and other minor water‐soluble phytochemicals. Quantitative data revealed a dimer of caffeoylmalic acid (0.73 mg mL −1 of juice), disinapoylgentibiose (0.64 mg mL −1 ), ferulic acid (0.56 mg mL −1 ), and isorhamnetin‐ O ‐sophoroside‐ O ‐malonyl(hexoside) (0.38 mg mL −1 ) as the predominant polyphenols. The results showed that WJ had dose‐dependent inhibitory potential against targeted enzymes, displaying a more potent inhibitory effect against α‐glucosidase relative to α‐amylase and lipase. WJ can be considered a potential complementary dietary approach to control hyperglycaemia and hyperlipidaemia, through inhibition of digestive enzymes. Practical applications Currently, raw watercress is widely consumed in liquid form, alone or together with other fresh vegetables, as an ingredient of the “detox juices.” Studies on watercress phenolic composition and antidiabetic properties have been performed on extracts, but not on juice, which is closer to the edible form. The present study supports consumption of watercress juice as source of phytochemicals potentially capable of inhibiting digestive enzymes linked to diabetes and obesity prevention/control.