Introduction: α-amylase is a major form of amylase found in humans and other mammals. It is the special key enzyme involved in carbohydrates breakdown. Inhibition of this enzyme could be used in treatment of diabetes. In this study, the effect of ten Iranian macrolichens on alpha amylase were tested. Methods: Different concentrations of the extracts (25, 50 and 75 mg/ml) were incubated with enzyme substrate solution and activities of enzyme were measured and acarbose was used as the positive control. Thin layer chromatography (TLC) and gradient-elution high performance liquid chromatography (HPLC) were used to determine the phytochemical compounds of the extracts. Results: The extracts showed a dose dependent inhibitory effect on amylase as Usnea articulata> Ramalina pollinaria> R. hyrcana > Cladonia rei> Flavoparmelia caperata> Parmotrema chinense> Punctelia subrudecta> P. borreri> Hyperphyscia adglutinata> Peltigera praetextata. The highest inhibition of amylase was 60% at extract concentrationa 75 mg/ml in U. articulata. TLC and HPLC for this species proved the presence of the compounds as usnic acid, fumarprotocetraric acid and protocetraric acid. Conclusion: This study showed that, macrolichens have inhibitory properties against α-amylase and determination of the type of enzyme inhibition by these macrolichen extracts could be provided by successful use of macrolichen chemicals as drug targets.
