The body of a herbaceous plant, Cistanche tubulosa (Schenk.) Wight, is used to make a medicinal preparation containing phenylethanoid glycosides and comprising 10 70% of echinacoside by weight of the preparation and 1 40% of acteoside by weight of the preparation. The medicinal preparation is used as an active ingredient of medicinal composition for use in prevention of senile dementia, and inhibition of aggregation of blood platelets.