ANTITUMOR-ACTIVITY IN AN EXTRACT OF THAI RICE SEEDLINGS

Antitumor activity was found in an extract of Thai rice (RD-7) seedlin gs, which had potent cytotoxic effects on four (P388, HSOS-1, X63-Ag8 and Jurkat) out of seventeen transformed cell lines, but not on untran sformed cell strains (YH-1, YH-3, KC-T1 and PAE). The activity was ver y weak, though significant, in dormant rice seeds, but it increased re markably from 3 d to 7 d after inoculation, decreasing again in the la ter stages of growth. The activity was concentrated by salting out wit h ammonium sulfate and partially purified by column chromatographies o f CM Sephadex (C-25) and Sephadex G-100. It was characterized as a pro tein-containing molecule with a molecular weight of 40 Kd which was re sistant to freezing, heating, and pH 5.0 and 9.0 environments, and sen sitive to trypsin digestion. The biological significance of this antit umor activity is discussed.