Bacillus subtilis BCRC 14715發酵黑豆萃取物之抗氧化活性及對血管收縮素轉化酶之抑制作用

Abstract

Bacillus subtilis為日本具機能性傳統發酵食品－納豆之菌酛。納豆具有抗氧化之生理功效，並含有血管收縮素轉化酶抑制劑(angiotensin-converting enzyme inhibitors, ACEI) 可預防血壓上升。本研究利用B. subtilis BCRC 14715對黑豆進行固態發酵，探討不同溶劑 (水、80%甲醇、80%乙醇、80%丙酮)之發酵黑豆萃取物所呈現之抗氧化活性及總酚，總類黃酮與花青素之含量。抗氧化活性所檢測之項目包括DPPH自由基清除能力、還原力及亞鐵離子螯合能力。此外，本研究並探討發酵期間Bacillus spp.發酵黑豆萃取物對血管收縮素轉化酶Angiotensin I Converting Enzyme（ACE）之抑制活性，並比較不同Bacillus菌株發酵黑豆及不同溶劑萃取物對ACE之抑制作用。 結果顯示，黑豆無論是否發酵均呈現具有抗氧化活性，惟發酵黑豆萃取物所呈現之抗氧化活性皆顯著高於（p<0.05）未發酵黑豆者。此外發酵黑豆不同溶劑萃取物中總酚、總類黃酮、花青素含量也顯著高於（p<0.05）未發酵黑豆者，其中又以丙酮萃取物中之總酚、總類黃酮及花青素之含量最高。黑豆及發酵黑豆萃取物所呈現之抗氧化活性，因溶劑之不同而有所差異。甲醇萃取物對亞鐵離子呈現有最佳之螯合能力。而丙酮萃取物所呈現對DPPH自由基清除能力及還原力最佳。 Bacillus spp.發酵黑豆之豆子或黏性物質萃取物，所呈現之ACE抑制活性皆隨發酵時間增長而提升，且因Bacillus菌株之不同而有差異，其中以Bacillus sp. CN11發酵黑豆者呈現之抑制活性最高。利用水、80% 乙醇萃取Bacillus spp. 發酵黑豆，在豆子部份以乙醇萃取物之ACE抑制能力較好，至於黏性物質部份則以水萃取物所呈現之ACE抑制活性顯著高於（p<0.05）乙醇萃取物。

Natto, a traditional fermented food in Japan, is prepared by fermenting steamed soybean with Bacillus subtilis. It has been reported to exert antioxidant activities, and the inhibitory effect on angiotensin I converting enzyme (ACE) as well. In the present study, various solvent (water, 80% methanol, 80% ethanol, 80% acetone) extracts of B. subtilis BCRC 14715-fermented black soybean were examined for total phenolic, flavonoid, and anthocyanin contents as well as the antioxidant activities including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals scavenging effects, reducing power, and Fe2+-chelating ability. Besides, effect of fermentation period and extraction solvent on ACE inhibitory activity of the Bacillus spp.-fermented black soybean extracts were also investigated. The results showed that the extract of the fermented black soybean exhibited significantly higher (p<0.05) total phenolic, flavonoid, anthocyanin contents and antioxidant activities than did the extract of the nonfermented black soybean. Among the various extracts examined, acetone extract showed the highest contents of total phenolic, flavonoid and anthocyanin. The methanol extract excerted the highest Fe2+-chelating ability, while the acetone extract showed the highest DPPH free radicals scavenging effects and reducing power. The inhibitory activity on ACE of bean and viscous material extracts of Bacillus spp.-fermented black soybean increased as the fermentation period was increased. Bacillus sp. CN11-fermented black soybean extract exhibited the highest ACE inhibitory activity. A higher ACE inhibitory activity was noted in bean extracted with 80% ethanol than with water. On the other hand, a significantly higher (p<0.05) ACE inhibitory activity was noted in the water extract of viscous material than the 80% ethanol extract.