Search for Edible Plant Constituents of Anti-Tumor Promotion Using an Inhibition Test of Epstein-Barr Virus Activation in Raji Cells

Abstract

Tumor promoting inhibitory properties (anti-tumor promotion) of edible plants including vegetables, fruits and marine algae have been studied by a convenient in vitro assay designed to detect the inhibition of tumor promter-induced Epstein-Barr virus (EBV) activation in Raji cells. Some of the anti-tumor promoters were then isolated, however it was rare that the anti-tumor promoter occurring in each active plant extract was specified. Thus, the anti-tumor promoting activity of the crude extracts was suggested to be frequently enhanced or reduced with co-occurring factors acting additively, synergistically, or antagonistically. As an attempt to find strongly active anti-tumor promoters, tropical Zingiberaceae plants used as condiments and occasionally also used as local medicine, have been focused on. From one of such species, Languas galanga, 1’-acetoxychavicol acetate (ACA) was isolated as a potent EBV activation inhibitor. ACA was also proven to be a highly active antitumor promoter by an in vivo test on mouse skin. Thus, the tropical Zingiberaceae plants may be a promising source of anti-tumor promoting food constituents. Details of the in vitro assay method, screening results of edible plants as well as some anti-tumor promoters are reported.