Yi L. Ngo and Lee S. Chua* Pages 97 - 103 ( 7 )
Background: There has been a great interest in the discovery of alternative medicines from medicinal herbs for type 2 diabetes, specifically screening for phytochemicals which are able to inhibit or delay glucose absorption.
Introduction: The aim of this study was to evaluate the inhibition of crude extract and rosmarinic acid rich fractions from Orthosiphon stamineus on α-amylase and α-glucosidase activities.
Methods: The plant crude extract was prepared by a reflux method using 70 %v/v ethanol, followed by fractionation using column chromatography to obtain rosmarinc acid rich fractions.
Results: The crude extract and its rosmarinic acid rich fractions showed a dose dependent manner to inhibit the saccharide hydrolysing enzymes. Fr. A (100 % rosmarinic acid) was found to have comparable performance with standard rosmarinic acid as an inhibitor for both enzymes. Approximately, 62.50 mg/mL and 5 mg/mL of Fr. A were sufficient to achieve almost 100 % inhibition against α- amylase and α-glucosidase, respectively. Rosmarinic acid in Fr. A (IC50 0.34 mg/mL) was found to be 5 times more active than the anti-diabetic drug acarbose (IC50 1.66 mg/mL) in the inhibition of α- glucosidase. Fr. B with 50 % rosmarinic acid (IC50 1.48 mg/mL) had an inhibitory power comparable to that of acarbose. Kinetic studies revealed that Fr. A inhibited α-amylase competitively, but displayed non-competitive inhibition towards α-glucosidase. Rosmarinic acid had higher affinity towards α-glucosidase with lower Michaelis-Menten constant (Km), 1.42 mM.
Conclusion: The findings suggest that rosmarinic acid rich fractions of O. stamineus could be a potential drug to regulate and manage type 2 diabetes mellitus.
Diabetes mellitus, fractionation, Orthosiphon stamineus, rosmarinic acid, α-amylase, α-glucosidase.
Metabolites Profiling Laboratory, Institute of Bioproduct Development, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Johor, Metabolites Profiling Laboratory, Institute of Bioproduct Development, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Bahru, Johor