Prostate cancer is the most commonly diagnosed cancer in males and one of the leading causes of cancer death. Although treatment options have increased for some patients, overall progress has been modest. Thus, there is a great need to develop new treatments. This invention relates to a method for treating cancer comprising using an anti-cancer compound of formula (I): More particularly, it relates to said anti-prostate cancer compound that can be isolated from Garcinia esculenta or chemically synthesized and its specific anticancer/antitumor activity. The invention has a specific application in treating human prostate cancer.