Huperzine A102518-79-6100 % similar (11E)-5-Amino-11-ethylidene-5,6,9,10-tetrahydro-7-methyl-5,9-methanocycloocta[b]pyridin-2(1H)-one120786-18-7100 % similar Huperzine B103548-82-945 % similar