Bufadienolides from the Venom of Bufo Bufo gargarizans and Their Enzyme Inhibition Activities and Brine Shrimp Lethality

A new bufadienolide named dyscinobufotalin (1), along with twenty known bufadienolides (2–21) were isolated from the venom of Bufo bufo gargarizans. Their structures were elucidated by spectroscopic analysis. The absolute configuration of the new natural product 2 was determined by X-ray single crystal diffraction and the complete NMR data for 3 was delivered for the first time. Both compounds 4 and 8 showed comparable α-glucosidase inhibitory activity (IC 50 values of 0.25 and 0.26 μM, respectively) to the positive control acarbose (IC 50 value of 0.42 μM), and 5 displayed potent inhibitory activity on acetylcholinesterase with an IC 50 value of 0.12 μM. Moreover, 5, 8 and 13 presented moderate toxicity against brine shrimp.