Cognitive-enhancing Phenylpropanoids of Scrophularia buergeriana Roots and their Action Mechanism

C ognitive-enhancing compounds from natural products have been searched by screening total extracts of natural products for the ameliorating activity against scopolamine-induced memory impairment in mice . In the course of screening, a methanolic extract of the root of Scrophularia buergeriana Miquel (Scrophulariaceae) was found to show a significant cognitive-enhancing activity. The dried roots of Scrophularia genus have been used in Oriental medicine for the treatment of fever, swelling, constipation, pharyngitis, neuritis and laryngitis. A number of iridoid glycosides, phenylpropanoids, terpenoids and flavonoids have been reported in the genus Scrophularia. To date, however, no precise correlation has been made between a particular constituent of these roots and an observed pharmacological activity except for effects on immunological activity. Subsequent fractionation of this extract using cognitive-enhancing activity as the screening parameter resulted in the isolation of four new phenylpropanoid esters of rhamnose (1 - 4), six phenylpropanoids (5 - 10), two phenylpropanoid glycosides (11 and 12) and a phenylalcohol (13). The new phenylpropanoid esters ha ve been characterized as 2-O-acetyl-3,4-di- O-E-pmethoxycinnamoyl- α-L-rhamnopyranoside (1), 2-O-acetyl-3-O-E-p-methoxycinnamoyl- α-L-rhamnopyranoside (2), 2- O-acetyl-3-O-Z-p-methoxycinnamoyl- α-Lrhamnopyranoside (3) and 4-O-E-p-methoxycinnamoyl-α-L-rhamnopyranoside