nicotiana tabacum tobacco,is a stout herbaceous plant in the solanaceae (nightshade family) that originated in the tropical Americas(South America,Mexico,and the West Indies)and now cultivated worldwide as the primary commercial source of tobacco, which is smoked or chewed as a drug for its mild stimulant effects.In addition, N.tabacum is also used as insecticides, anesthetics,diaphoretics,sedatives,and emetic agents in Chinese folklore medicines because of its containing many useful chemical compounds.Previous investigation of this species led to the discovery of a number of new compounds that showed various bioactivities,such as anti-HIV-1, anti-TMV and cytotoxicity by our groups. In continuing effortsto the phytochemistry research on the roots and stems of K326 led to the isolation of three new isocoumarin derivatives(1-3)and three known phenolic compounds(4-6)