25% sodium chloride solution and 7% sodium bicarbonate aqueous solution were added to the organic solution, and then the aqueous layer was separated. Methanol (5.0 vol) was added to the organic solution, which was followed by the filtration through activated carbon. The activated carbon was washed with a mixture of methanol (0.9 vol) and ethyl acetate (2.1 vol). The mixed filtrate was concentrated under reduced pressure to 9.0 vol, and then methanol (1.0 vol) and ethyl acetate (2.0 vol) were added to the concentrate.