Five compounds were isolated from the chloroform-soluble fraction of the methanolic extract of the dried rhizomes of Zingiber officinale (Zingiberaceae) through repeated column chromatography. Their chemical structures were elucidated as 4-, 6-, 8-, and 10-gingerols, and 6-shogaol using spectroscopic analysis. Among the five isolated compounds, 6-shogaol exhibited the most potent cytotoxicity against human A549, SK-OV-3, SK-MEL-2, and HCT15 tumor cells. 6-shogaol inhibited proliferation of the transgenic mouse ovarian cancer cell lines, C1 (genotype: $p53^{-/-}$, c-myc, K-ras) and C2 (genotype: $p53^{-/-}$, c-myc, Akt), with $ED_{50}$ values of 0.58 ${mu}M$ (C1) and 10.7 ${mu}M$ (C2).