Four new neuroprotective iridoid glycosides from Scrophularia buergeriana roots

Four new iridoid glycosides were isolated from a 90% MeOH extract of Scrophularia buergeriana roots and characterized as 8-O-E-p-methoxycinnamoylharpagide (1), 8-O-Z-p-methoxycinnamoylharpagide (2), 6′-O-E-p-methoxycinnamoylharpagide (3), and 6′-O-Z-p-methoxycinnamoylharpagide (4), respectively. In addition, three known iridoids were identified as E-harpagoside (5), Z-harpagoside (6), and harpagide (7). Compounds 1-7 significantly attenuated glutamate-induced neurotoxicity when added to primary cultures of rat cortical cells at concentrations ranging from 100 nM to 10 μM. The results obtained indicate that the iridoid glycosides isolated from S. buergeriana have significant protective effects against glutamate-induced neurodegeneration in primary cultures of rat cortical neurons.