Method for preparing water extract of ashwagandha leaves which has enhanced anti-cancer activity utilizing cyclodextrin, and pharmaceutical composition containing ashwagandha leaves

The present invention addresses the problem of providing a method for preparing a water extract of ashwagandha ( Withania somnifera ) leaves, whereby it becomes possible to increase the amounts of withanone and withaferin A, which are active ingredients, in the water extract of ashwagandha leaves. The present invention also addresses the problem of providing a pharmaceutical composition containing ashwagandha leaves in an economically advantageous and simple manner. The present invention relates to: a method for preparing a water extract of ashwagandha leaves, which is characterized by comprising extracting ashwagandha leaves in the presence of cyclodextrin; and a method for enhancing the anti-cancer activity of a water extract of ashwagandha leaves. The present invention also relates to a pharmaceutical composition for treating or preventing cancer, which contains a water extract of ashwagandha leaves. The present invention further relates to a pharmaceutical composition containing a dried powder of ashwagandha leaves and cyclodextrin.