The invention relates to a new
bilobalide B compound. The
bilobalide B compound is extracted from
ginkgo leaf; and the
bilobalide B content in the bilobalide B compound is greater than 99%. The bilobalide B compound contains bilobalide A of which the content is lower than 0.4%. The invention also relates to a preparation method of the bilobalide B compound, which comprises the following steps: under stirring conditions, adding kieselguhr and
ginkgo leaf extract, heating under
reflux at 78-85 DEG C for 0.5-1.5 hours, filtering and concentrating; adding
distilled water, removing impurities, separating out the
ethyl acetate layer, passing the
ethyl acetate layer through an peracidic aluminum
oxide column, eluting with water saturated
ethyl acetate, and collecting the eluate; concentrating the eluate under reduced pressure until no ethyl acetate smell is emitted, adding a proper amount of
ethanol to dissolve the concentrated eluate, adding water until the
ethanol content is 60-70%, standing, precipitating coarse
crystal, filtering, taking the coarse
crystal, and
drying; and recrystallizing the coarse
crystal sequentially with
ethanol and ethyl acetate to obtain the finished product bilobalide B compound.