Bio-guided fractionation of essential oils looking for plant bioactive secondary metabolites with potential hypoglycemic activity

Diabetes mellitus is a chronic metabolic disorder characterized by a difficulty in blood glycaemia maintenance. People in the world with diabetes have increased dramatically over recent years and still are increasing. A possible therapeutic approach for treating diabetes mellitus is to decrease postprandial hyperglycemia, by inhibiting the carbohydrate hydrolyzing enzymes, such as α-amylase. Thanks to its inhibition, carbohydrate digestion is stopped, and as a consequence glycaemia reduces. Examples of such inhibitors used in the clinical practice for treating diabetes are acarbose, miglitol and voglibose [1]. However, these drugs are known to be associated with various gastrointestinal side effects, among others diarrhea [2],3].

The aim of this study is the research for new α-amylase inhibitors deriving from plant secondary metabolism. A bio-guided fractionation approach, based on an in vitro α-amylase inhibition assay, was adopted to isolate and identify the active fractions/compounds in different essential oils. Eighty-four essential oils obtained by distillation from different plant species and botanical families were submitted to the enzymatic assay.

Three essential oils resulted particularly active (Eucalyptus radiata A.Cunn. ex DC., Laurus nobilis L. and Myristica fragrans Houtt.) with an inhibitory capacity comparable or slightly higher than acarbose, chosen as positive control. The obtained results showed that all essential oil components seem to play a synergic effect. Moreover, an interesting number of both hydrocarbon and oxygenated compounds were characterized by a good α-amylase inhibition, around 30%. These preliminary results demonstrate that essential oils may represent a promising source of potential α-amylase inhibitors.

• References

• 1 Bailey CJ. New Approaches to the Pharmacotherapy of Diabetes, Vol. 2, 3rd Edition. Blackwell Science Ltd; UK: 2003: p.73.1-73.21
• 2 Fujisawa T, Ikegami H, Ogihara T. Metabol. 2005. 54: 387-390