The Effects of Aged Garlic Aqueous Extracts on Toxicity Caused by Hydroxyl Radical Species

黑大蒜水萃取物對羥基自由基引起毒害的效應影響

陳淑玲(Shu-Ling Chen) ； 梁致遠(Ji-Yuan Liang) ； 苑舉民(Jeu-Ming P. Yuann)

《MC-Transaction on Biotechnology》 8卷1期 (2016/03) Pp. 1-14

摘要

先前研究顯示，野生白大蒜烘培處理15 天或更久之後，其總還原力、總多酚含量、DPPH清除能力較白大蒜為高。於本研究中，我們針對不同製備天數(0-20 天)黑大蒜水溶萃取液對清除更為活躍之氫氧自由基(^‧OH)之活性作檢測。在核糖降解實驗中，所有大蒜水溶液皆造成核糖降解，而非清除^‧OH。降解程度以白大蒜最高，5-10 天烘培黑大蒜逐漸遞減。之後，20 天烘培黑大蒜使核糖降解程度略為回升。於DNA 完整測試，^‧OH 會造成超螺旋DNA，pGEM-7zf(-)，之瓦解，白大蒜使完整DNA 比例略為回升，黑大蒜則有更強^‧OH 清除能力，且其隨烘培天數增加而上升。於細胞內DNA 完整測試，20天烘培黑大蒜清除能力則較白大蒜略低。電子順磁共振光譜儀實驗顯示，黑大蒜萃取液對於^‧OH 自由基產物，DMPO-OH，降低效果遠不及白大蒜萃取液。本研究顯示，大蒜烘培後，抗氧化活性雖有所增加，然而於此梅納反應過程中，若干活性成分亦有所轉變。

關鍵字

黑大蒜 ； 羥基自由基 ； 去氧核糖 ； 質體DNA ； 電子順磁共振光譜儀 ； 芬騰反應

並列摘要

Previous study shows that aged garlic dried for 15 days and beyond exhibited the highest levels of total reducing power, total polyphenol content, and DPPHscavenging ability. Here, the effects of a more diffusible radical species, hydroxyl radical (^‧OH), generated via a Fenton-type reaction were evaluated to examine its toxicity in the presence of aged garlic aqueous extract. In ribose degradation assay, the amount of ribose degraded by ^‧OH in the presence of aged garlic dried for 0-10 days was shown to decrease from 0- to 10-day drying, but slightly increase with garlic prepared by 20-day drying. In DNA integrity assay, the relaxation of supercoiled plasmid DNA, pGEM-7zf(-), due to DNA single-stranded breakage caused by ^‧OH was diminished in the presence of aged garlic aqueous extract with 20-day drying garlic reaching plateau, consistent with the radical scavenging effects observed previously. We also developed an assay to examine the ^‧OH toxicity on the integrity of plasmid DNA within E. coli since ^‧OH is a neutral species that can cross cell membranes without much difficulty. In the integrity assay of DNA transformed into E. coli, aged garlic aqueous extract of 20-day drying was shown to exhibit a slightly lower protecting ability against ^‧OH, compared to its wild garlic counterpart. Lastly, to resolve these conflicting results, an EPR spectrometer was used to examine the radical scavenging effects of both wild and aged garlic dried for 5 to 20 days. We found that wild garlic exhibited a much stronger effects on scavenging ^‧OH, whereas aged garlic lost much of this ability regardless the time of their fermentation.

並列關鍵字

aged garlic ； hydroxyl radical ； 2’-deoxy-D-ribose ； plasmid DNA ； EPR ； Fenton’s reaction