Three new compounds from the litters of Casuarina equisetifolia

Two new cyclic diarylheptanoids, casuaritriol A (1) and casuaritriol B (2), were isolated from the EtOAc extract of litters (including branches and leaves) of Casuarina equisetifolia, along with a new triterpene casuariene (3), and two known compounds diarylheptanoids adanin (4) and ostryopsitriol (5). Their structures were elucidated by spectroscopic analysis (including HRESIMS, 1D NMR and 2D NMR data), and the absolute configuration of 3 was determined by analysis of the ECD data according to the octant rule. Compound 1 exhibited inhibitory activity against α-glycosidase with inhibition rate of 45.1 ± 1.4 % at a concentration of 500 μg/mL. In addition, compound 4 showed weak inhibitory activity against acetyl cholinesterase (AChE) with inhibition rate of 14.9 ± 1.1 % at a concentration of 50 μg/mL.