Inhibitory effects of Zijuan tea ( Camellia sinensis var.kitamura) extracts on angiotensin converting enzyme, α-amylase and pancreatic lipase in vitro

Objective: To explore whether the extracts of Zijuan tea has the potential to anti-hypertensive, anti-hyperglycemic and anti-obesity. Methods: The crude polyphenol fraction ( defined as ZTE₁) was extracted from Zijuan tea. ZTE₁ was then separated to the precipitated ( defined as ZTE₂) and the soluble ( defined as ZTE₃) with ethyl acetate.Subsequently, delphinidin-3-O-β-D- ( 6- ( E) -p-coumaroyl) galactopyranoside ( AN₃) and cyanidin-3-O-β-D- ( 6- ( E) -p-coumaroyl) galactopyranoside ( AN₄) were purified from ZTE₂. The inhibitory activities of the three crude fractions and two anthocyanins towards angiotensin converting enzyme ( ACE) , α-amylase and pancreatic lipase were evaluated comparing with epigallocatechin gallate ( EGCG) .The inhibitory type of AN₃ and AN₄towards ACE, α-amylase and pancreatic lipase was also explored.Results: All the Zijuan tea extracts had inhibitory activities towards the three enzymes.The inhibitory activities of ZTE₃ towards the three enzymes, ZTE1 towards α-amylase and pancreatic lipase, ZTE₂ towards α-amylase were stronger than EGCG.Furthermore, ZTE₃ had the highest inhibitory acitivity against ACE, whereas ZTE₂ and ZTE₁ had the highest inhibitory acitivity against α-amylase and pancreatic lipase, respectively. And the inhibitory activity of AN₃ towards α-amylase was not significantly different to EGCG.The inhibitory activity of AN₃ was higher than AN₄ towards all the three enzymes. In addition, AN₃ and AN₄ were noncompetitive inhibitors of ACE, α-amylase and pancreatic lipase with Ki values of 0.33, 0.37 mmol/L, 0.39, 0.41 mg/m L and 0.22, 0.78 mg/m L.Conclusion: The extracts of Zijuan tea has the potential to anti-hypertensive, antihyperglycemic and anti-obesity.