Discovery of diterpenoid and sesquiterpenoids as α-glucosidase inhibitors from the leaves of Pieris formosa

Two new compounds, a norditerpenoid and a megastigmane sesquiterpenoid, were isolated from the ethyl acetate extract of Pieris formosa leaves collected in Yichang, Hubei, China, together with eight known megastigmane sesquiterpenoids. Their structures were elucidated by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Pormoside A ( 1 ) represents the first example of a 17- β - D -glucopyranosyloxy-substituted 14,15-di- nor -cyclophytane diterpenoid. All isolates were evaluated for α -glucosidase inhibitory activity. Pormoside A ( 1 ) (IC 50 = 112.90 ± 3.98 μ M) showed significantly more potent inhibition than the positive control acarbose (IC 50 = 219.55 ± 3.95 μ M). Molecular docking studies of pormoside A and B further revealed their binding interactions with α -glucosidase. ● Ten compounds, including a new diterpenoid and a new sesquiterpenoid, pormoside A–B ( 1 – 2 ), were isolated from Pieris formosa . ● Pormoside A ( 1 ) is the first 17- β - D -glucopyranosyloxy-conjugated 14,15-di-nor-cyclophytane diterpenoid. ● The absolute configurations of pormoside A–B ( 1 – 2 ) were determined by ECD calculations. ● Pormoside A ( 1 ) showed α -glucosidase inhibitory activity comparable to acarbose. ● Molecular docking explored active compounds' interactions with α -glucosidase.