Method for preparing effective monomer of total alkaloid extract of holarrhena antidysenterica and application thereof

The invention discloses a method for preparing an effective monomer of a total alkaloid extract of holarrhena antidysenterica and application thereof. The method comprises the following steps of: (1) refluxing and extracting holarrhena antidysenterica by using 90 percent ethanol to obtain an ethanol extract; (2) dissolving the ethanol extract in water, regulating the pH value to be between 1 and 2 by using concentrated hydrochloric acid, and filtering; (3) regulating the pH value of filtrate obtained after the filtration to be between 9 and 11 by using stronger ammonia water or aqueous solution of sodium hydroxide, and extracting by using an organic solvent to obtain the total alkaloid extract of the holarrhena antidysenterica; and (4) performing MCI-gel column chromatography, methanol aqueous solution gradient elution, and thin-layer chromatography on the total alkaloid extract, wherein obtained effective monomer ingredients comprise conessine, isoconessimine, conessimin and conimin.The invention discloses application of the total alkaloid extract of the holarrhena antidysenterica in preparing medicaments for preventing and treating Alzheimer disease or medicaments for improvingintelligence, and application of the effective monomer ingredients of the total alkaloid extract of holarrhena antidysenterica in preparing the medicaments for preventing and treating Alzheimer disease or the medicaments for improving intelligence.