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       【摘要】 
       ObjectiveIn order to make full use of the resources of longan seed and avoid wasting, the approach of extracting the total flavanone of longan seed was provided in this artical.MethodsThe flavonoids extracted from longan seed with ethanol was checked and determined using spectrophotometry. ResultsUsing this method, the contents of the total flavanone of longan seed was C=1.634 mg/ml and the recovery rate was 99.65%.ConclusionThis method provides a purely physical and non-contaminative process for the whole extraction procedure. It is an ideal way to extract the flavanone of longan seed, and the outcome and the purity of the flavanone are all very high .
       【关键词】  Ethanol-extraction; Longan seed; Total flavanone; Identification
       
        Longan is a kind of green tree in sapindaceac longan. There are a lot of common names for the fruit of longan as follows: Long mu、Asian litchi chinesis、Sichuan billard ball、Pure black horse bead、Yan luan、Honey spleen、Jiaolei、Wooden bomb, etc. It is one of famous subtropics fruits in our country［1］.Longan has more than 2000 years history and a very wide distribution in the world, such as the south of China, the north of Vietnam"s. It is an import ant green longevity fruit in the south Asian tropics.
        The fruit of longan has a good demand at home and abroad. It is widely cultivated in China, including the provinces of Fujian, Guangdong, Guangxi, Taiwan, Hainan, Yunnan, Sichuan, Guizhou, and the product of longan from China is the highest in the world.
        In China, longan has been used as traditional medicine for a long time. Shizhen Li said that food takes litchi chinesis as the expensive, and hut profits take the longan as the excellent in his famous book Native Chinese Plants. “Longan is considered as a good fruit and an important raw material with high nutritional value. Longan can keep man intelligent, make man have good appetite.” said the book Chart after Book on Chinese Medicine written by Song Su. As a traditional medicine, longan has many curative effects on the illness of weakness, agrypnia, forgetfulness, terror and so on. In addition, the longan shell, longan nucleus, dragon vertigo, the dragon eyelid, and the root all can be compounded in medicine. Longan nucleoluses can also prevent pain, hemorrhage,hernia, mange and skin diseases［2,3］. At the same time, in longan nucleoluses, some kinds of alkaloid and fatty oil are also contained. So longan can be powdered and burned to treat the wound.  “Longan should be a necessary medicine in family, for it has favorable effect on stanching and making the wound recover quickly.”［4］, this can be found in the book of Compendium Appropriates Lost Articles. Longan nucleoluses occupy 17% of the gross weight of longan fruit. However, thousands tons of longan nucleoluses are wasted every year［5］. In order to make full use of its natural resources, longan nucleoluses must be studied further. At present, there has been little report about total flavanone in longan nucleoluses. In this paper, the study on longan nucleoluses is provided.
       1  Instruments and reagents
       1.1  InstrumentsKQ5200DB numerical control ultrasonic wave purifier (Kunshan supersonic instrument limited company); UV-755B ultraviolet visible spectrophotometer (Shanghai analysis instrument main plant); ZF-I three uses the ultraviolet analyzer (Shanghai to attend to village photoelectricity instrument plant); SHB-III water-circulation type multifunction vacuum pump (Zhengzhou great wall scientific industry and trade co.ltd ). 800B centrifuge (on Hai"an pavilion scientific instrument factory).
       1.2  Reagents 
       95% Ethyl alcohol; Sodium nitrite AR; Aluminium nitrate AR; Sodium hydroxide AR; Aluminum trichloride AR; Hydrochloric acid AR; Ammonia water AR; Glacial acetic acid AR; Ethyl acetate AR; Magnesium acetate AR; Methyl alcohol AR; Magnesium powder AR; Normal butyl alcohol AR; Standard rutin (Chinese drugs biological preparations examination); Hydrogen peroxide solution AR; Ferrous sulfate AR; Salicylic acid AR.
        Longans nucleuses originates from the Guangxi Baise.
       2  Methods and result
       2.1  Total flavanone ingredients withdraw 
       Clean fresh longan seeds were dried and powdered. 50g of the powder was extracted 2 times with 80ml 95% alcohol. The reagents were eliminated under low pressure, then 95% alcohol with the same volume were added to the extracts and cooled for 2h in refrigerator. The extracts were filtrated, then the solution was condensed to 25ml approximately, and transferred to the 25 ml measuring flask, deluted with 60% alcohol to the scale.
       2.2  Basis of determinationIn order to detect the contents of total flavanones in the seeds of longan, the aluminum ion reagent was added to the unknown solution under the condition of suitable value and the stable characteristic absorption peak was obtained with the comparision of standard solution of flavanone by the method of spectrophotometry .
       2.3  Determination of total flavanone
       2.3.1  The optimum wavelength0.03ml 5% NaNO2 and 0.3ml 10% Al(NO3)3 were added to the standard solution of total flavanone. In the condition, chelate compounds were formed. The optimum wavelength was got at 510nm by the method of spectrophotometry from 420nm to 700nm with the comparision of blank reagents.
       2.3.2  Standard CurvesThe standard solution of total flavanone (0.1 mg/ml) 0.00, 0.50, 1.00, 2.00, 3.00, 4.00, 5.00 ml were added to 10.0ml-flask respectively, 0.30 ml 5% NaNO2 was added to each flask, shaked up. After 6 minutes, 0.30 ml 10% Al(NO3)3 was added in each flask, shaked up. In the next 6 minutes, 4 ml 4% NaOH solution was added to them, deluted with 60% alcohol to the scale, shakeed up. Put them quietly. The data of absorption peak were obtained by spectrophotometry at 510 nm.Table 1  determination of absorbance by ultraviolet visible spectrophotometer（略）
       2.3.3  Determination of the extracts0.50 ml sample solution was added to 10.0 ml flask. The solution was prepared by the same method in procedure 2.3.2. According to the regressive equation: A=-2.208×10-2 + 13.757 8 C, total flavanones content was C=1.634 mg/ml.
       2.3.4  Recycling experiments0.05 ml standard solution of total flavanones and 0.50 ml solution of sample were added to 10.0ml-flask. The same substances and reagents were added to the flask by the same operation. The return ratio was 99.65%.
       2.4  Experiments of total flavanones distinction
       2.4.1  The color-reactionReaction under the ultraviolet ray. The sample solution was dripped on the filter paper. The yellow color appeared in visible light and the dust color and the fluorescence spot appeared with the ultraviolet ray.
        Reaction with AlCl3: The sample solution was dripped to the filter paper. 1% AlCl3 solution of alcohol was added to the filter paper, dried. Yellow appeared with the visible light and the decadent fluorescence spot appeared with the ultraviolet ray.
        Reaction with the water of strong ammonia:
        The solution of sample dripped to the filter paper. The paper was fumigated with ammonia, and the obvious fluorescence spot could be observed immediately.
        Reaction with Mg(AC)2:
        The solution of sample dripped to the filter paper, 1% Mg(AC)2 solution of methyl dripped on it, dried. Yellow spot could be seen on the paper with ultraviolet ray,
        Reaction with Mg and hydrochloric acid:
        1 ml of the solution of sample was put in the test tube, then the powder of Mg was put in it. Several drops of hydrochloric acid dripped to the solution. Purple-red colors appeared in the forth place.
       2.4.2  Paper chromatographicThe solution of sample dripped on the paper. The developing agent was n-bityl-acetic acid-water(4:1:5).After the paper chromatographic,1%AlCl3 solution of alcohol sprayed to the paper, dried. The yellow spot could be found with the ultraviolet ray.
       3  Discussion
       3.1  ConclusionThe experiment is simple and the recovery-ratio is 99.65%. The total flavanones obtained by this method can be identified as an excellent route. The method of extraction and purifying is a physical process without any pollution. The route has a good prospect.
       3.2  PrespectFalconoids belong to the kind of Chinese medicine. It has a great prospect by developing this medicine. The series of flavonoid, including double hydrogens, double flavanones, flavanols, alkones, orange alkones, new yellow ketones and so on, are one of the kind of natural products［6］. The natural flavanones can be absorbed by human body because of its small-molecular structure. Therefore, flavanones can provide many function of treatment: such as eliminating tirness brain, preventing aging, protecting blood vessel, promoting blood cycling. At present, flavanones provided some new functions of treatment, for example, anticancer, anti-inflammation, stopping pain, anti-oxidation, reducing blood sugar, anti-virus, anti-radiation, and so on［7～12］. In recent years, developing natural products to make new drugs has been focused all over the world. The kind of flavanones must be studied and developed to created more drugs.
        The paper shows that flavanones are abundant in longan nucleuses. It is significant to make full use of longan necleuses. It has a brilliant prospect in developing this natural resources.
        
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