Chemical Profiles And Antioxidant Properties Of Ginseng Extracts Obtained By Subcritical Water Extraction

Ginseng(Panax ginseng C.A.Mey)is a well-known traditional Chinese medicine and novel food,which contains a variety of bioactive components,such as the ginsenosides,polysaccharides and polyphenols.Currently,the extraction of these bioactive components always depends on conventional solid-liquid extraction methods,which is time-consuming,energy-inefficient,and involves some organic solvents that are potentially toxic to the environment or human health.Subcritical water extraction(SWE)is emerging as an environmentally friendly technology in recent years and has been used extensively for extracting active ingredients from natural plants.However,there is little research considering the utilization of SWE to extract active ingredients from ginseng.In order to assess the feasibility of SWE technology for extracting active ingredients from ginseng,systematic comparison of chemical constituents and antioxidant activities in ginseng extracts obtained from SWE and conventional extraction methods vere conducted.The following results were obtained:(1)SWE was significantly affected by the extraction temperature in terms of extraction yields on total sugar(TS),total protein(TPro)and total phenolic components(TP).The optimized temperature for TS and TP was 200 OC,and the highest yields were 67.87±0.75 mg GE/g and 24.84±0.11 mg GAE/g,respectively.The highest yields of TPro was at 180?,reaching 24.83±1.16 mg BSAE/g.SWE showed significantly and markedly higher extraction yields on TS,TPro and TP than traditional hot water(WE)and ethanol(EE)extraction methods.(2)A quantitative method for the determination of ten ginsenosides,including R1,Rb1,Rb2,Rb3,Rc,Rd,Re,Rg1,Rg2 and Ro,was established based on ultrafast liquid chromatography tandem mass spectrometry(UFLC-MS/MS)technology.The results showed that the ginsenosides in the subcritical water extracts all decreased significantly with the increase of extraction temperature except for Rg2,which reached the highest extraction yield at 160?(2.1 mg/g),and it may be attributed to the degradation and conversion of ginsenoside Re and Rb1 under high temperature environment in SWE.The total extraction yields of ten major ginsenosides obtained from SWE were extremely lower than EE(20.2 mg/g).(3)The ABTS and DPPH free radical scavenging activities of ginseng extracts obtained from SWE were significantly higher than that of WE and EE,and increased with the increasing temperature.The antioxidant activity showed a positive correlation with TP yield.UFLC·MS/MS analysis revealed that there were six polyphenols(protocatechualdehyde,ferulic acid,isoferuhc acid,luteolin,quercetin,and apigenin)in SWE extracts,among which protocatechulc aldehyde,luteolin,quercetin and apigenin may be responsible for the enhancement of antioxidant activity with increasing temperature.The Maillard reaction occurred during SWE,and the reaction process was significantly accelerated when the temperature was over 180?.In summary,SWE is an environmentally friendly and efficient extraction technology with promising applications.It can be used to extract active ingredients from ginseng roots,such as polysaccharides,proteins,polyphenols and ginsenoside Rg2.But the hydrolysis of constant ginsenosides,for instance Rb1 of Re,and Maillard reactions may be accompanied with the increases of extraction temperature.