女貞子的抗氧化特性探討及對於糖尿病之應用研究

女貞子在台灣是一種常見的食用植物。先前研究指出，此種植物果實具有抗發炎、保肝及抗氧化的活性。而賦予這些活性的是女貞子所含有的三帖類，如：齊墩果酸及熊果酸。然而到目前為止，直接食用女貞子或當作補充劑對於促進健康的機轉仍不清楚。因此本研究的第一部份，將針對女貞子的水萃取物及乙醇萃取物進行非酵素型的抗氧化作用的評估分析，分析包括：還原力、金屬離子的螯合作用及自由基的清除能力。先前許多研究指出，具有抗氧化活性的物質也極有可能可以作為預防糖尿病的策略。糖尿病腎病變是眾多糖尿病併發症中的一種，而腎病變會加重糖尿病的嚴重性。在本研究的第一部份中，已發現女貞子所含有的三帖類-齊墩果酸及熊果酸具有抗氧化的活性，然而齊墩果酸及熊果酸對於糖尿病所引發的氧化及糖化壓力的抑止作用仍不清楚。因此，本研究的第二部份將進一步研究觀察齊墩果酸及熊果酸對於糖尿病小鼠腎臟中糖化終產物的抑制作用及影響。研究結果證實，女貞子的水萃取物及乙醇萃取物中含有數種具有抗氧化作用的酚酸、類黃酮及三帖類（齊墩果酸及熊果酸）。在糖尿病鼠的實驗中，女貞子中的齊墩果酸及熊果酸可以有效抑制腎臟中醛糖還原酵素的活性及促進第一型乙二醛酵素的活性，進而降低腎臟中糖化終產物的累積及改善腎臟功能。因此，藉由飲食補充齊墩果酸及熊果酸或是含有此三帖類的女貞子將有助於預防或治療糖尿病引起的腎臟疾病。

Glossy privet fruit (Ligustrum lucidum Ait.) is a common edible plant in Taiwan. It has been reported that this fruit possesses anti-inflammatory, hepatoprotective, anti-aging and antioxidative activities and these activities may be ascribed to its triterpenes and/or glucosides components such as oleanolic acid and ursolic acid. So far, it remains unknown that taking this fruit directly or as a supplement could contribute to the healthy effects. In the first study, we designed to evaluate the non-enzymatic antioxidant capacities, including reducing power, metal ion chelating effect, and scavenging activity for radicals, of aqueous and ethanol extracts from this edible plant. Many researches showed that agents which possess antioxidant activities may be a better strategy used to prevent diabetes. Diabetic nephropathy is one of diabetic complications, which exacerbate the severity of diabetes. In our previous studies, it implied that these triterpenes of glossy privet fruit possess antioxidant activities, however, it remains unknown that these two compounds could ameliorate diabetic oxidative and glycative stress. Therefore, further study was to investigate the inhibitory effects of oleanolic acid and ursolic acid on AGEs production in the kidney of diabetic mice.Based on our results, we found that aqueous and ethanol glossy privet fruit extracts contained phenolic acids, flavonoids, and two triterpenes (oleanolic acid and ursolic acid), which possess efficient antioxidative effects. Moreover, oleanolic acid and ursolic acid occuring in glossy privet fruit could markedly suppressed renal aldose reductase activity and enhanced glyoxalase I activity, which contributed to decrease renal AGEs formation and improve renal functions of diabetic mice. Therefore, the supplement of oleanolic acid and ursolic acid or foods rich in these compounds might be helpful for the prevention or treatment of diabetic kidney diseases.