LAUSR

Carcinostatic effects of combined use of ascorbic acid (Asc), 2- O -phospho- or 6- O -palmitoyl ascorbate (Asc2Phos, Asc6Palm) or diverse alkanoyl Asc, and nano-sized platinum-poly( N -vinyl-pyrrolidone) colloid (PVP–Pt; 2-nm diameter) were examined on human esophagus carcinoma-derived cells KYSE70. Cell viability was repressed by ‘Asc6Palm + PVP–Pt’ mixture more markedly than by Asc6Palm or PVP–Pt alone, together with cell shrinkage and fragmentation, in contrast to no additive carcinostatic effect of ‘Asc + PVP–Pt’ or ‘Asc2Phos + PVP–Pt’. The effects might be partly due to efficiency for intracellular uptake of PVP–Pt, as previously shown by our studies that Pt atoms composed of PVP–Pt were incorporated into human tongue carcinoma cells by 9.6-fold compared to normal human tongue epitheliocytes. Asc6Palm was advantageous for intracellular uptake, in terms of the proper balance for molecular hydrophilicity–lipophilicity (BMHL), whereas 6- O -stearoyl (C 18 ) Asc or 2,6- O -dipalmitoyl (2 × C 16 ) was demonstrated to be less carcinostatic owing to a lower BMHL. Although esterolytically converted from Asc6Palm, Asc was necessitated to be retained for efficient carcinostasis, and demonstrated by HPLC–coulometric ECD analysis to be appreciably stabilized in electrolytically generated hydrogen (dissolved hydrogen: 0.575 mg/L)-water, but scarcely in hydrogen-gas-bubbled water (0.427 mg/L), Mg stick-derived hydrogen (0.044 mg/L) water, or tap water, suggesting that hydrogen-rich water suppresses oxidative decomposition of Asc. Thus, Asc6Palm plus PVP–Pt with hydrogen-rich water supplement might be applicable for carcinostatic therapy.