Effects Of Cooking On The Nutritional Components Of Rhizome And The Antioxidation Of Polyphenols In

Water caltrop stem is a new type of aquatic vegetable, but only a few people recognize the edibility of the Water caltrop stem. Polyphenols are the most abundant bioactive substances in water caltrop stem, and water caltrop stem polyphenols have strong bioactivities and deserved to be researched further. At the present study,the effect of different cooking methods on nutritional quqlity of water caltrop stem was studied. We also studied the extraction, purification and antioxidation of polyphenols from the water caltrop stems.The aim of this research is to provide data support for the development of water caltrop stem as a new resource of aquatic vegetables and data references for its polyphenols used as a natural antioxidant.(1)Water caltrop stem was to be deal with by blanching, microwaving and oil frying for different minutes(1,2,3,4,5min). And the nutrimental composition of water caltrop stem was detected and analyzed. The result indicated that cooking treatments led the greatest decrease of the contents of ash, mineral substance,vitamin C, polysaccharide, crude fiber, crude protein, soluble protein, polyphenol and flavones. Blanching treatment increased the moisture content, while, microwaving and oil frying decreased the moisture content. Oil frying treatment increased the fat content,while, blanching and microwaving showed little effects.Generally, microwave cooking can better preserve the nutrients of water caltrop stem.(2)The polyphenol of water chestnut stem was extracted by ultrasonic. The influence of various factors such as ethanol concentration, time, solid-liquid ratio,temperature on the extraction rate of polyphenol was discussed in detail.And On this basis,the response surface methodology was used to optimize the extraction of polyphenol. The result indicated that the best technology condition were temperature 50℃, time 20 min, ratio of solid to liquid 1:30(g/mL),concentration of ethanol 30%.(3)Used macroporous resin AB-8 to purify the water caltrop stem polyphenol. And the effect of adsorption and desorption time, sample concentrations, sample flow rates and elution rates were studied. The result indicated that the best purification condition of the polyphenol were the sample concentration of 2mg/mL, sample flow rate of 2mL/min,50% ethanol elution, 2mL/min desorption rate. With this condition, the purity of the stem polyphenols reached to 79.26%(4)The antioxidant activities of the purified polyphenols were evaluated in vitro by scavenging capability of DPPH free radical, hydroxyl free radical and total antioxidant capability test. The result indicated that the polyphenols had a good antioxidant activity in vitro. Compared withVc, the water caltrop stem polyphenols has the same strong activity of scavenging DPPH free radicals within certain range, and weaker activity of scavenging hydroxyl free radicals and total antioxidant capability. But water caltrop stem polyphenols has a good antioxidant effect in general.(5)Adopted low dose (100mg/(kg·d))、middle dose (200mg/(kg·d)) and high dose (400mg/(kg·d)) of water caltrop stem polyphenol to filled the stomach of ICR male mice for 4 weeks, and the saline was used as control. So we could know the effects of different dose of water caltrop stem polyphenol to mice body weight,organ index,total anti-oxidant capacity,T-AOC; glutathione peroxidase, GSH-Px; superoxide dismutase, SOD and malondialdehyde,MDA. The result indicated that the T-AOC activity, SOD activity and GSH-Px activity were increased, and the content of MDA was significantly decreased compared with control mice. It showed that the polyphenol has a significant antioxidant effect, and it is a kind of high efficient natural antioxidant.