| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 99 === In this study, soymilk was fermented by co-cultures of Streptococcus thermophilus BCRC 14085 and Bifidobacterium infantis BCRC 14633. Various solvent (water, 80% methanol, 50% acetone) extracts of soymilk and fermented soymilk were prepared. Effect of the prepared extracts against the proliferation of human colon cancer cells, Caco-2 and HT-29, as well as on the cytotoxicity and genotoxicity induced by 4-nitroquinoline-N-oxide (4NQO) toward Int-407 were then investigated. Besides, the effect of fermentation on the contents of total phenolic, flavonoid, saponin and phytate in soymilk was examined.
Results showed that the extracts of the fermented soymilk and unfermented soymilk all reduced the proliferation of cancer cells. Extract of the fermented soymilk exhibited a significantly higher (P <0.05) antitumor cell proliferation effect than did the respective unfermented soymilk extract. Among the various extracts examined, methanol extract of fermented soymilk showed the highest antitumor cell proliferation effect.
Methanol extracts of both soymilk and fermented soymilk were found to show dose-dependent suppression effect on the cytotoxicity and genotoxicity of 4-NQO against Int-407. While these effects were significantly higher (P <0.05) with fermented soymilk extract than the non-fermented soymilk extract. Fermentation length affected the anticytotoxicity of the fermented soymilk extract with extract of the 32-h fermented soymilk showed the highest anticytotoxicity. Study on the possible anticytotoxic mechanism of methanol fermented soymilk extract revealed that it was essentially the descytotocic effect, interaction with 4-NQO, which contributed to the reduced cytotoxicity of 4-NQO.
Additionally, content of total phenolics increased, while the content of saponin and phytate reduced in soymilk after fermentation. On the other hand, fermentation did not cause a significantly change in the content of flavonoid.
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