Pentacylic triterpenes from Lavandula coronopifolia : structure related inhibitory activity on α-glucosidase.

Ten pentacyclic triterpenes ( 1 - 10 ) were isolated from Lavandula coronopifolia. We evaluated their α -glucosidase inhibitory activity, and found that the aglycones, 1 , 2 , 3 , 4, 7 and 10 showed superior IC ₅₀ values to the positive control. In order to explain the structural requirements for α -glucosidase inhibitory activity, eleven derivatives were prepared, including one new compound, 2-formyl-(A)1-19 α -hydroxy-1-norursane-2, 12-dien-28-oic acid 10c . The results demonstrated that a free hydroxyl at ring-A and a free carboxylic group at position 28 are key structural features for the α-glucosidase inhibitory activity, also that an ursane skeleton is optimum for the activity. Additionally, enzyme kinetic analysis of pomolic acid 2 , the most potent compound, revealed that it inhibited α -glucosidase in a mixed-type manner. The molecular docking simulation validated this type of inhibition and highlighted the role of the C-3 hydroxyl and C-28 carboxylic groups in interaction with the enzyme in silico .