| Abstract: | 心血管疾病與癌症為現代人生命健康的二大殺手，而心血管疾病中動脈粥狀硬化是主要的致死原因，動脈粥狀硬化會引起血栓、中風與心肌梗塞等疾病而致死。而低密度脂蛋白（low density lipoprotein；LDL）的氧化修飾在早期的動脈粥狀硬化中扮演很重要的角色，藉由抗氧化的作用來抑制LDL的氧化修飾，是一種有效預防動脈粥狀硬化發生的方法。桑椹是一種天然植物果實具有豐富的植物色素成分，而具有抗氧化活性，本研究之目的為評估由桑椹所分離的萃取物(水萃取物: MWEs；花青素萃取物: MACs)，其抗LDL氧化及抗動脈硬化之作用效果，而進行體外抗氧化實驗與細胞實驗，最終驗證於動物實驗結果。
以銅離子誘導LDL氧化的模式進行體外抗氧化實驗，並以LDL氧化時其蛋白部分的氧化修飾反應與脂質部分的過氧化反應作為氧化指標。藉由ApoB衍蛋白斷裂現象及LDL蛋白表面電荷改變的程度與脂質過氧化產物MDA及diene的生成量均減少的結果發現，MWEs與MACs 具有抑制LDL氧化的能力，此外也具有清除DPPH（1,1-diphenyl-2-picrylhydrazyl）自由基的作用。而在細胞實驗方面，桑椹萃取物也具有保護巨噬細胞不受因LDL氧化作用而死亡，也會減少巨噬細胞轉形為泡沫細胞（foam cell），這些現象都會減緩動脈硬化的發生過程。最後由動物實驗的結果顯示，以高膽固醇飲食誘導動脈硬化生成的兔子，其血清中的總膽固醇量會因有同時餵食桑椹萃取物而降低，且其動脈中動脈粥狀硬化的損傷面積也比只以高膽固醇飲食餵食的兔子減少許多。
由上述體外抗氧化實驗與細胞實驗及動物實驗結果顯示，桑椹萃取物具有極佳的抗氧化活性並能抑制LDL的氧化，此外也參與調控巨噬細胞因LDL的氧化而產生促進動脈粥狀硬化生成的反應。綜合以上結果，我們認為桑椹萃取物具有預防動脈粥狀硬化的作用，而能應用於保健食品的開發。
Atherosclerosis, a disease occurring in arteries, is one of the primary causes of heart diseases and stroke. The complications of atherosclerosis often lead to death. The oxidative modification of low density lipoprotein plays a key role in the pathogenesis of atherosclerosis. Antioxidative reagents, which can effectively inhibit LDL oxidation, may prevent atherosclerosis via reducing early atherogenesis, and slowing down the progression to advance stages.
As shown in previous studies Mulberry is a nature fruit containing a lot of pigments that was found to possess antioxidative activity. In this study, we evaluated the antioxidative activity of the mulberry extracts, mulberry water extracts (MWEs) and mulberry anthocyanins extracts (MACs) by measuring their effects on LDL oxidation (in vitro) and anti-atherosclerotic abilities (in animal). The antioxidative activity of the extracts on LDL oxidation was defined by Apo B fragmentation, relative electrophoretic mobility (REM), thiobarbituric acid-relative substances (TBARS) assay and diene conjugation. Our results showed that MWEs and MACs were able to inhibit the Apo B fragmentation, REM, TBARS assay and delay the diene conjugation in the Cu2+-mediated oxidative LDL. MWEs and MACs also possessed the ability of DPPH radical scavenging. Taken together, both MWEs and MACs showed strong potency to inhibit the LDL oxidation induced by copper. Further studies demonstrated that MWEs and MACs could reduce the cholesterol accumulation in macrophage, and that, subsequently, inhibit the formation of foam cells. In the in vivo experiment, male New-Zealand rabbits fed with a 1.3% cholesterol diet were used as the animal model. The results showed that the New-Zealand rabbits fed with the MWEs and high cholesterol diet revealed a less extent of the atherosclerotic lesion and total cholesterol concentration than the animals fed only with a high cholesterol diet.
In conclusion, mulberry extracts, mulberry water extracts (MWEs), and mulberry anthocyanin extracts (MACs) possess strong antioxidative ability to inhibit LDL oxidation and foam cell formation. Therefore, it is suggestive the mulberry could be a healthy food to prevent individuals from atherosclerosis. |
