乳酸發酵豆奶抑制結腸癌細胞增生及4-NQO對Int-407細胞毒性之作用

Abstract

本研究利用Streptococcus thermophilus BCRC 14085和Bifidobacterium infantis BCRC 14633對豆奶進行共同發酵。接著以不同溶劑 (水、80%甲醇、50%丙酮) 對豆奶及發酵豆奶進行萃取，檢測發酵豆奶萃取物抑制結腸癌細胞株HT-29和Caco-2增生及其抗4-nitroquinoline-N-oxide (4-NQO) 誘導腸道細胞株Int-407細胞與基因毒性之效果，並檢測萃取物中總酚、總類黃酮、皂素及植酸含量。 結果顯示，無論是豆奶或發酵豆奶萃取物均具有抑制癌細胞增生之效果，其中發酵豆奶萃取物抑制癌細胞增生之效果顯著高於(P <0.05)未發酵者。而在不同溶劑萃取物中，又以發酵豆奶甲醇萃取物之抑制效果最佳。 豆奶及發酵豆奶甲醇萃取物對於抑制4-NQO誘導Int-407之細胞毒性和基因毒性結果呈現劑量效應，其中發酵豆奶所呈現的抑制效果顯著高於(P <0.05)未發酵者。發酵時間會影響抗細胞毒性之效果，由結果中發現發酵豆奶甲醇萃取物以發酵32小時之抗細胞毒性效果最佳。進一步探討發酵豆奶甲醇萃取物抗細胞毒性之機制，發現其效果主要來自去致毒性作用(descytotocic effect)，使4-NQO不活化進而減少4-NQO之細胞毒性。 此外，豆奶於發酵後其總酚含量增加，而皂素及植酸含量降低。然而發酵並未使類黃酮含量有顯著之改變。

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.