| Imbalanced production and consumption of reactive oxygen species (ROS),leading to oxidative stress, is implicated many disease, such as cancer, arteriosclerosis, malaria and rheumatoid arthritis, as well as neurodegenerative diseases and ageing processes. Some studies show an inverse association between the daily consumption of fruits and vegetables and the development of chronic diseases. The protective effects of fruits and vegetables have long been attributed to their antioxidant compounds, such as polyphenols, carotenoids, and vitamins C and E. Besides playing an important role in physiological systems, antioxidants have been used in the food industry to prolong the shelf life of foods, especially those rich in polyunsaturated fats. The synthetic antioxidants, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) has been widely used industrially to control lipid oxidation in foods. However, the use of these synthetic antioxidants has been questioned due to their potential health risks and toxicity. Therefore, the search for antioxidants from natural sources has been received much attention and It's urgent to find suitable antioxidants to replace synthetic ones.Persimmon (Diospyros kaki) is widely cultivated in Japan, Korea, China, Brazil and Italy. It contains many bioactive compounds, such as polyphenols, flavonoids, terpenoids, steroids, dietary fiber, carotenoids and minerals. In China, its fruits and leaves were traditionally used for many medicinal purposes such as coughs, hypertension, dyspnoea, paralysis, frostbite, burns and bleeding, Persimmon fruits were also reported to antioxidant activity and free radical scavenging effects. However, persimmon peel (PP) that contains higher phenolics than persimmon pulp is usually discarded during dried persimmon manufacture and there have been few experimental studies about antioxidant activity of active compounds in PP. Therefore, PP was chosen as research materials. The objectives of this investigation was to provide experimental basis for development and utilization of PP as raw materials of natural antioxidants by determining the main effective components and antioxidant activity of persimmon peel extracts (PPE). First, the effective components of PP were extracted by counter-current extraction with reflux, and were concentrated before macroporous resin (DA201) purification. The contents of effective component were determined before and after purification. Then, the antioxidant activity of PPE and protective effects of PPE on rat liver mitochondria were investigated by various in vitro chemical simulation systems. The main studies were three parts as follows:Part I:Preparation of PPE and determination of the effective component contents, including total sugar, total polyphenols, total flavonoids.Part II:The antioxidant activity of PPE was evaluated by several common antioxidant methods in vitro:scavenging activities of free radicals (DPPH·, O2-·and·OH), reducing power, total antioxidant capacity and inhibition of lipid peroxidation.Part III: The protective effect of PPE on rat liver mitochondria induced by free radical were evaluated. The effects of PPE on inhibiting lipid peroxidation, swelling, protein oxidation, and protecting ATPase as well as scavenging activity on O2- were measured in mitochondria.1. Preparation of PPE:PPE was prepared under these conditions:the concentration of ethanol was 70%, the ratio of solid to liquid was 1:10, the extraction temperature was 80℃and the extraction time was 2 hours (twice), respectively. The rude extraction was concentrated at 50℃(PPEo) and was purified with macroporous resin (PPE1), and the yields of PPE0 and PPE1 were 18.10%,4.17%, respectively. The contents of effective components were determined in PPEo and PPE1, it was found that the total flavonoids (25.85%) and total polyphenols (47.05%) contents of PPE1 increased four times compared with PPEo, while the total sugar (15.63%) decreased three times.The results showed that macroporous resin has better purification on flavonoids and polyphenols.2. The antioxidant activity of PPE: The results showed that PPE had markedly antioxidant ability in vitro several antioxidant methods, especially the antioxidant activity of PPE1 was higher than PPE0. The IC50 of PPE1 on scavenging DPPH·, O2-·1as well as·OH was 0.057 mg/mL,0.137 mg/mL,0.425 mg/mL, respectively. In addition, similar results with free radical scavenging were showed in reducing power, inhibition of lipid peroxidation and total antioxidant capacity. Generally, there is a close correlation between antioxidant activity and contents of flavonoids and polyphenols in extracts.3. The protective effects of PPE1 on rat liver mitochondrial: In the present study, we found that PPE1 could effectively protected liver mitochondrial membranes from lipid peroxidation and had scavenging activity on 02-·with IC50:0.083 mg/mL,0.119 mg/mL, respectively. In addition, PPE1 has been shown to protect ATPase as well as to inhibit the mitochondrial swell and protein oxidation in a dose-dependent. The protective effects of PPE1 on mitochondrial may be contributed to scavenging O2·or block chain reaction of lipid free radicals, as well as, PPE1 might inhibit membrane permeability transition and reduce production of protein carbonyl.In conclusion, our results showed that PPE had visible antioxidant activity and protects rat liver mitochondrial from oxidative stress, suggesting the pharmacological potential of PPE against pathological processes related to oxidative stress. PP is not only feedingstuff additives but also will be made an raw material of new nuture antioxidant. |
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