Effects Of Thermal Processing On Phenolic Components,Antioxidant Activities And Conversion Mechanisms Of Saponins In Flowers And Pulps Of Panax Ginseng C.A.Meyer

Panax ginseng C.A.Meyer a perennial herb,belongs to the Araliaceae family.At present,there are many researches on its underground part of the ginseng plant,but few researches on its aboveground part,especially those on ginseng flowers and pulps.Heating,as a common method in preparation of Chinese medicinal herbs,were widely applied to ginseng process.In this paper,ginseng flower and pulps were processed with different heating methods,at temperatures and for different durations,and those methods of Folin-Ciocaltus,DPPH,as well as HPLC and UPLC-QTOF-MS/MS were adopted to determine the contents of total phenolic,to evaluate the antioxidant activities,and to estimate ginsenosides and newly generated chemical component.Results are as follows:1 A method for simultaneously qualitifing and quantitatifing 20 ginsenosides in Panax ginseng flowers and pulps by HPLC technique was established in this paper.The method provides a reasonable theoretical basis for evaluation of the thermal processing effect on ginseng flowers and pulps.2 Two thermal strategies,i.e.,steaming and baking,were carried out toward ginseng flowers:temperature was set up at 100,120,150 or 180? in baking and 100 or 120? in steaming,duration were fixed for 1,2,4 or 6 h.Results show that with the enhancement of temperature and duration,both steaming and baking treatments would lead to increases of both the total phenols and antioxidant activities,with those of the only B180 treatment(i.e.,baking at 180?)as an exception.The peak numbers and heights of polar ginsenosides(retention time between 25-90 min)decreased,and the less-polar ginsenosides(retention time between 110-140 min)increased.Polar ginsenosides were abundant in baked or steamed ginsengs at lower temperatures,whereas less polar ginsenosides occurred and enriched at higher temperatures.Compared with baking treatment,steaming was much more efficient in transforming ginsenosides.UPLC-QTOF-MS/MS results show that baking and steaming caused a 3.2-fold increase in ginsenoside species existed in unheated ginseng flowers(20/64 ginsenosides).Moreover,both the two heating methods triggered ginsenoside acetylation and thus caused formation of 23 acetylginsenosides.Finally,a new transformation mechanism concerning acetyl-ginsenosides formation was proposed.3 The steaming treatment were next carried out on ginseng pulps.Temperature was set up at 100 or 120?,duration was fixed for 1,2,4 or 6 h.Ginseng pulps were prepared with two methods:extract from soak supernatant of ginseng pulps with 100%alcohol(GPS)and ultrasonic extract from ginseng pulps with 70%alcohol(GPE).Results show that total phenol and antioxidant activities increased effectively in steaming GPS.Peak numbers and heights of polar and less polar ginsenosides increased in S100(i.e.,GPS steamed at 100?),but polar ginsenosides decreased and less polar ginsenosides increased in S120.Thus,we speculated that the thermostability of ginsenosides in ginseng pulps was relatively low.GPS much higher than GPE in total content of 18 ginsenosides,but steaming treatment led to decrease in total content of the 18 ginsenosides in all treatments,and the best treatment are E1001(i.e.,GPE steamed at 100?)and S1001(i.e.,GPS steamed at 100 0C for 1 h).UPLC-QTOF-MS/MS results show that steaming caused a roughly 2-fold increase in ginsenoside species existed in GPS and GPE(24/44 ginsenosides).Moreover,6 malonyl ginsenosides were detected in GPE and GPS,and 10 acetyl ginsenosides were detected only in steaming treatment.Finally,a new transformation mechanism concerning acetyl-ginsenosides tranformation and malonyl-ginsenosides degradation was proposed.