| Litchi (Litchi chinensis Sonn.) is a tropical fruit of the Sapindaceae family originating from South-east Asia, with a bright red attractive pericarp surrounding a white aril. In recent years, some active ingredients extracted from litchi already have aroused people's interest. Many studies have demonstrated that anthocyanin, phenolic acid and polysaccharide compounds existed in the aril, seed and flower of Litchi, and had several physiological functions such as that can used in industrial production and lead to an efficient natural nutraceutical or antioxidant drug. Therefore, as an important source, choosing an optimal cultivar litchi pericarp for further development means much for improving the by-product value of litchi fruit, facilitating the development of related agro-industry and environmental protection. In this study, the procyanidins from licthi pericarp were extracted in optimal conditions, and the construction identified preliminarily. Then, the procyanidins from eight cultivars of licthi pericarpe evaluated and compared the particle size distribution, color and antioxidant activity in different systems, and showed good correlations with the antioxidant activity, and antimicrobial activity of LPPC against 4 kinds of microbes was studied.The results of this research are follows:1. The objective of this study was to give the optimal conditions for extraction of procyanidins from litchi pericarp (LPPC). The extraction effects of methanol, ethanol and acetone were compared by HPLC. The result showed that the optimum conditions based on single factor and orthogonal test were as follows:by used of 80% (V/V) ethanol as solvent, a material-solvent ratio 1:20 (W/V) and extracted 3 times at 50℃, pH 6.0 for 120 minutes. Under these conditions, the extraction yield was more than 90%. The extract was concentrated and separated by column packed AB-8 resins. The purity of coarse extraction was 87.45%, the yields of procyanidins was 1.3%. Then the influences of extraction temperature, solvent concentration and extraction time were analyzed according to response surface methodology experiment, and the extract was concentrated and separated by column packed AB-8 resins. Based on the canonical analysis, the optimum extraction conditions were obtained as follows:68.48% ethanol as solvent at 61.65℃for 105.52 minutes.2. LPPC was identified preliminarily by analysis of the infrared Spectra and ultraviolet-visible spectroscopy.7 Chinese cultivars litchi pericarp procyanidins (LPPC) ethanol extracts was purified by AB-8 column macroporous resin and Toyopearl HW-40S resin. The majority oligomer, (-)-epicatechin, trimeric procyanidins and A-type dimmer, were also identified by reverse phase HPLC and UPLC, significant differences were observed in the concentration of these compounds.3. Particle size distribution and color value of 8 cultivars extraction from litchi pericarp were compared. The results indicated that Baila LPA in 35% enthoal showed the best particle size distribution (2.48-6.51μm), and D50 was 4.56μm and BET area was 498.23 m2/kg. However, different kinds of LPA showed significant different of particle size distribution. At the same time, Nuomici LPA showed the best C*(110.27) and a*(87.12), and Feizixiao showed the best L*(94.86) and b*(98.79). Moreover, there was a big correlation between anthocyanins and L*,a*,b*,C* and H°.3. The antioxidant activities of 8 cultivars LPPC were evaluated and compared by various in vitro antioxidant assays. In general,'Huaizhi'showed highest antioxidant activity in hydrogen peroxide (H2O2), superoxide radical (O2·-) scavenging and ferric reducing;'Feizixiao' exhibited the highest scavenging 2,2-diphenyl-1-picrylhydrazyl radical (DPPH-), hydroxyl radical (OH·) and lipid peroxidation inhibition activities, while 'Guiwei'showed the highest value of antioxidant activity based onβ-carotene bleaching and ferrous chelating assay. A high positive correlation existed between for procyanidins and oligomer procyanidins between their content and DPPH·, H2O2, OH·and O2·- scavenging and ferric reducing activity. These results suggest that litchi pericarp can be used as antioxidant and nutritional sources, and 'Huaizhi','Feizixiao' were the optimal cultivars. Furthermore, all extracts exhibited significant higher level of antioxidant activity than ascorbic acid and the composition of 8 LPPC showed good correlations with the antioxidant activity. These results showed 8 LPPC could be a potential nature source of antioxidant. 4. The antimicrobial activity of LPPC against 4 kinds of microbes was studied. The results indicated that the basic structural unit of LPPC mainly contains cyanidin. Meanwhile, the antimicrobial effect of LPPC on microbes were discovered and showed a positive correlation with the concentration of LPPC. The diameter of inhibition zone of Escherichia coli, Staphy lococcus aureus and Saccharomgces cerevislac in oxford plate assay were 15.1,14.0 and 13.8 mm, respectively. The maximum inhibitory rate just reached 28.75% to Aspergillus niger under the concentration of 10mg/mL. By plate dilution method in order to observe their minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of LPPC, the result showed that Escherichia coli and Staphy lococcus aureus with the MIC and MBC at 2.5 mg/mL, however, Saccharomgces cerevislac and Aspergillus niger had the same MIC at 5 mg/mL and no bactericidal ability. v...
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