Two New Indole Alkaloids from Toad Venom of Bufo bufo gargarizans

Two new indole alkaloids, Bufotenidine B (2) and Bufocarboline A (6), along with seven known indole alkaloids (1, 3-5, and 7-9) and three organic acids (10-12), were isolated from the water extract of toad venom. The structures of the new alkaloids were elucidated by extensive spectroscopic methods. The absolute configurations of 4, 6, and 8 were determined for the first time by electronic circular dichroism (ECD) calculations. The cytotoxic activity of all compounds was tested against human malignant melanoma cells A375 by the MTT method, and no antitumor activity was observed.