Study On Polyphenol Composition,Antioxidant And Digestive Enzyme Inhibitory Activity Of Subcritical Water Extract Of Chestnut Shell

The chestnut shell is rich in polyphenols,and if it can be fully utilized,good economic and ecological benefits can be obtained.At present,the traditional solid-liquid extraction method mainly be used to extract the polyphenols in the chestnut shell,which takes along extraction time and has a low efficiency.And the application of organic reagents can lead to the potential environmental pollution and health hazards.In recent years,subcritical water extraction technology,an emerging,green and pollution-free extraction method,has been widely used in the extraction of active components of natural products.However,there is no corresponding report on extracting polyphenols from chestnut shells by the subcritical water extraction technology.In order to evaluate the feasibility of the extraction of polyphenols from chestnut shell by this extraction technology,we analyzed the changes of polyphenol composition,antioxidant activity and the regular pattern of digestive enzyme inhibitory activity in chestnut shell when the temperature changes compared with acetone reflux extraction(AE),methanol reflux extraction(ME),acetone ultrasonic assisted extraction(AUE),methanol ultrasonic assisted extraction(MUE)and traditional hot water reflux extraction(WE)method.The main findings are as follows(1)The polyphenol component in the subcritical water extract of chestnut shell is significantly affected by the extraction temperature.The dry matter yield and total phenolic content of chestnut shell extract increased significantly with the increase of subcritical water temperature,and peaked at 220℃,14.82 ± 0.14%and 746.71 ± 3.35 mg GAE/g,respectively.It is higher than AE,AUE,ME,MUE and WE extraction methods,and has the advantages of shorter extraction time,simple operation and low energy consumption.(2)Based on high performance liquid chromatography-tandem mass spectrometry(HPLC-MS),we established the qualitative and quantitative detection method of 18 polyphenols,such as epigallocatechin,protocatechuic aldehyde and ferulic acid in chestnut shell extract.The results showed that the content and type of polyphenols increased with the increase of temperature when the temperature ranged from 120℃to 160℃.however,when the temperature exceeded 180℃,the content of polyphenols showed a downward trend,which may be the higher water diffusion rate due to the raise of extraction temperature leading to the diffusion and dissolution of polyphenols.but,some thermally unstable polyphenol components in the extract will degrade when the temperature is too high.Our results indicated that the total extraction rate of polyphenols from chestnut shell by subcritical water extraction technology was significantly higher than by traditional water extraction or organic solvent extraction,but the composition of the extract was significantly affected by the temperature.(3)The subcritical water extracts of chestnut shells under different temperatures have a significantly higher scavenging activity for ABTS,DPPH free radicals and FRAP iron ions than traditional hot water extraction,organic solvent extraction and organic solvent ultrasonic assisted extraction.However,the antioxidant capacity of subcritical water extracts is significantly affected by the extraction temperature.When the extraction temperature is gradually increased,the antioxidant capacity is first decreased and then enhanced,the lowest at 140℃,the highest at 220℃,and the ABTS at 220℃.The antioxidant activity equivalents of DPPH and FRAP were 4.83 ± 0.05,4.15 ± 0.01,30.57±0.17 mM Trolox/g,respectively.The antioxidant capacity of the chestnut shell extract is significantly correlated with the total phenolic content.(4)All of the subcritical water extracts of chestnut shells with different temperatures have the activities of inhibiting α-glucosidase and α-amylase,and the inhibitory effect is significantly higher than obtained extracts by the traditional extraction methods.The subcritical water extract at 120℃ had the best inhibitory effect on α-glucosidase and α-amylase that the IC50 values were 0.012 and 0.017 mg/mL,respectively.And the inhibitory activity was significant stronger than that of acarbose,and the inhibition are also competitive and reversible.