Reticulatin, a novel C-spiroterpenoid from the lichen growing in Vietnam.

A novel C-spiroterpenoid, reticulatin (), was isolated from the lichen (Taylor) M. Choisy (Parmeliaceae). Five previously-reported compounds were also isolated: zeorin (), leucotylin (), lupeol (), betulinic acid (), and dihydroreynosin (). The structures were elucidated by 1D, 2D NMR, and HRESIMS spectroscopy and comparison with the literature. We propose that reticulatin is a biosynthetic product of fusicoccadiene and vinapraesorediosic acid A Diels-Alder addition. Reticulatin is the first C-spiroterpenoid identified from lichen metabolites. All compounds were evaluated for inhibition of glucosidase. Compound showed the most potent inhibition, with an IC value of 3.90 μM, much lower than that of the acarbose positive control (IC 165 µM).