A Preliminary Study On Extraction Of Total Flayonoids From Grape Leaves And Its Application In Wine Brewing

Flavonoids in grape and wine has stronger ability of anti-oxidation, and higher health protective function to human being. At present, most of the research were mainly focus on the study of flavones and its utilization in gape berries.In fact, the contents of total flavonoids in grape leaves are much high then that of the fruits, and the contents of flavonoids are found closely related to folia antioxidant activity. Grape leaves fall off annually and always makes these abundant resource wasted every year. Therefore, for the effective utilization of these resources, in this research, we firstly detected the contents of total flavonoids in leaves of different species and cultivated varieties in vitis resources, and then using Yan73(Vitis vinifera L.) as experimental materials, carried out researches about the extraction, purification technologies of total flavonoids from grape leaves. And we also studied the dynamic changes of contents and antioxidant activity of total flavonoids during the wine fermentation process. The results of the study is in the purpose to provide some basic knowledge for further use of grapevine leaf flavonoids. The main research results are as follows:1. Total flavonoids contents in leaves of13species of wild grape and11cultivated varieties were detected, and the results showed that the cultivar Xiahei has the highest content of total flavonoids (63.28mg/g). Otherwise, leaves of cultivar Zhengdawuhe contains the lowest content of total flavonoids (16.31mg/g). Among the detected samples the different significance varied from "a" to "o". Leaf total flavonoids content in wild vitis resources varied from21.42mg/g to59.50mg/g. The contents in leaves of Cabernet Sauvignon from Qiubei county and Deqin county are31.80mg/g and39.68mg/g, respectively. Wild vitis resources Vitis heyneana Roem.et Schult. from Songming county and Qiubei county, Yunnan province both are growing in the wild condition, the total flavonoids contents in leaves were59.50mg/g、24.21mg/g, respectively, different significantly. In addition, blade flavonoids contents in same varieties but from different geophysical and climate vineyards were also different significantly, implied the leaf flavonoids contents of grape are influenced by both the genotype and environmental factors. The average content of total flavonoids in all the detected samples were35.53mg/g, however total flavonoids contents in leaves of Vitis heyneana (fromQinbei, Yunnan province), V. davidii (from Hunan province) and Vitis bryoniifolia Bunge (from Kunming, Yunnan province) were59.50mg/g,56.10mg/g,52.4mg/g, respectively, significantly high than the average content of35.53mg/g, will be potentially good resources for flavonoids.2. After exploring the extraction conditions by single factor experiments and combined with a orthogonal test, the optimum condition for grape total flavonoids extraction is:using80%ethanol with the extraction temperature at80℃,1:50solid-liquid ratio,10min treatment time of ultrasonic, with the total extraction time is4h. Under these conditions35.03mg of total flavonoids can be extracted from each gram of grape leaves.3. Using AB8macroporous resin purified the extracts, the best adsorption time is60min, and desorption time is120min with the ethanol volume fraction of60%. It can promote the total flavonoids contents of extracts from10.22%to24.67%. Using ethyl acetate, n-butanol extraction, combined with the AB8macroporous resin adsorption, has good purification effect to flavonoids, can effectively increase the flavonoids content from10.22%to58.8%. And the DPPH radical scavenging and total antioxidant abilities are positively correlated with the flavonoids contents of extracts.4. During the process of yeast culture, to add20mg,40mg and60mg leaf extract into100ml medium, respectively, hadsome effects was seen to the growth of yeast but a certain of promotion. However, the concentration of80mg/100ml of the extract in medium can significantly inhibit the reproduction of yeast. During all the process of fermentation, total content of flavonoids in the system had no significant variation. Adding certain amount of grape leaf extract to wine whenever before or after the process of fermentation can all effectively increase the content of total flavonoids and promote the antioxidant ability of wine.