| Guava as a high-value cash copes is widely cultivated in south of china. It contains alot of polyphenols. Studies have shown that plant polyphenols have many physiologicalactivities, such as antineoplastic, antibacterial, antioxidant and so on. In order to make fulluse of the resources of guava, this paper conducted a preliminary study about theextraction, separation and purification of the guava polyphenols and the quantitativeanalysis of the simple phenolic acid, as well as the anti-oxidative and anti-microbialactivity. The main contents and results are as follows:1. We used microware assisted extraction to extract the polyphenols in guava, andconducted the single factor experiment, finally used response surface methodology tooptimize the extraction process. The results showed that the optimum technologicalcondition of microware assisted extraction were as follows: micro ware power was490W，ethanol concentration was50%，solid-liquid ratio was1:21(m/v)，extraction time was130s. Under this technological condition, the extraction rate can reach1.78±0.38mg/g.2. The guava polyphenols were purified and separated by NKA-9macroporous resinand SephadexLH-20, obtained four different components, which is GP1, GP2, GP3andGP4. Based on the results of characteristic color reaction and ultraviolet spectral analysis,we confirmed that the components are all polyphenols. Then using HPLC andUPLC-MS/MS to conduct the quantitative analysis of the simple phenolic constituents, theresults suggested that: after purified by NKA-9macroporous resin, the purity of guavapolyphenols is45.7%, recovery rate is81%; guava polyphenols contains gallic acid,protocatechuic acid, catechin, quercetin, kaempferol and chlorogenic acid. In GP1, thehighest ingredient was catechin (69.4mg/kg), followed by gallic acid (23.99mg/kg), andthe content of kaempferol is the lowest; In GP2, the gallic acid content was529.74mg/kg,which is the highest level in four components; In GP3, the content of catechin (2191.49mg/kg) was higher than other components, but the kaempferol content (0.25mg/kg) waslower than the other component; Quercetin was the peculiar composition of GP4; thecontent was32.38mg/kg.3. With ascorbic acid (Vc) as positive control, the total antioxidant capacity and thescavenging capacity of hydroxyl radical, superoxide anion free radical and DPPH freeradical were used to evaluate the antioxidant capacity of the crude polyphenols (CGP), themacroporous purification polyphenols (PGP) and other separate components of guava polyphenols. The results showed that guava polyphenol had high antioxidant activity, thetotal antioxidant activity was GP4>VC>GP3>GP2>PGP>CGP>GP1. The guavapolyphenols can effectively scavenge hydroxyl radical, superoxide anion free radical andDPPH free radical, and within a certain range, the free radical scavenging capacity had alinear relationship with concentration. The scavenging ability of guava polyphenols oneach free radical was not consistent, crude polyphenols and GP1had the best eliminatingeffect on fhydroxyl radical, and the macroporous resin purification of polyphenols had thestrongest scavenging capacity on DPPH and superoxide anion radical. Guava polyphenolscan easily cleanup the DPPH radical, its linear concentration range and50%inhibitingconcentration is the lowest, followed by the scavenging ability on hydroxyl radical.4. Using the inhibitory zone diameter as evaluation index, the antibacterial activity ofguava polyphenol was measured, and studied the antimicrobial stability of it by usingStaphylococcus aureus as indicator bacteria, the results showed that: guava polyphenolshad a good inhibitory effect on Staphylococcus aureus, Escherichia coli, Listeriamonocytogenes, Pseudomonas aeruginosa, Shewanella putrefaciens and Bacillus subtilis,except for the MIC of Listeria monocytogenes and Shewanella putrefaciens are below5mg/mL, the rest MIC are all below2.5mg/mL. When pH was at4~5, the antibacterialactivity of guava polyphenol was the strongest, and its antibacterial activity had a goodstability to temperature and ultraviolet radiation, while low salinity will promote itsantibacterial activity. |
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