| Dehydroepiandrosterone(DHEA)was the most abundant sterol in human blood.As early as the 20 th century,DHEA was known as the "mother of hormones".DHEA not only participated in the synthesis of a variety of steroid hormones,but also had various physiological effects such as anti-cancer,treatment of obesity,prevention and treatment of diabetes,regulation of immunity,protection of nerves,and improvement of ovarian function.DHEA was commonly found in animal tissues and organs,and the method of obtaining exogenous DHEA was mainly artificial synthesis.Common synthetic methods required multiple chemical reactions,which were complicated and difficult to control.Sweet potato was one of the few plant raw materials that were known to naturally contain DHEA.Its planting area and output in China rank first in the world,with a wide range of sources.Therefore,using sweet potato as raw material to extract and prepare DHEA to meet the needs of DHEA products in the food,medicine,and health care industries has important practical significance.In this study,sweet potatoes were used as raw materials,the DHEA high-performance liquid phase detection system was optimized systematically,the Aspergillus oryzae fermentation extraction technology was used to optimize the extraction process parameters.On this basis,the differences in the content of DHEA in 19 kinds of sweet potatoes were analyzed and compared,and the functional properties of DHEA such as anti-oxidation and anti-aging were investigated.The main research contents and conclusions were as follows:(1)The DHEA standard product was used as the research object,the DHEA retention time and the correlation coefficient of the standard curve were used as the inspection indicators to optimize the DHEA high-performance liquid chromatography detection system;LC-MS/MS was used to qualitatively identify the DHEA extract prepared by the fermentation pre-test of Aspergillus oryzae.The extract was used to verify the reproducibility of the optimal detection conditions for DHEA.The results showed that increasing the organic phase ratio,speeding up the flow rate of the mobile phase,and increasing the column temperature can shorten the peak time of DHEA and increase the separation efficiency of DHEA.Qualitative analysis confirmed that the extract contained DHEA.The best detection conditions for DHEA high performance liquid chromatography were as follows: methanol/water(v/v)80/20,column temperature 42°C,flow rate 0.4 m L/min,detection wavelength 200 nm,injection volume 10 ?L,the RSD of the standard precision test was 3.23%.Under this condition,the DHEA retention time was 11.496 min.The sample separation efficiency was good,and it was far away from the solvent peak.The RSD of the sample repeatability test was 3.06%.The sample recovery rate reached 90.16%.These results showed that the optimized DHEA high-performance liquid chromatography detection system had good precision,repeatability,stability and high recovery rate.(2)In order to innovate the Aspergillus oryzae fermentation and extraction process of DHEA from sweet potato,single factors experiments were used to discuss the influence of fermentation temperature,inoculum amount,fermentation time,fermentation solid-liquid ratio,peptone addition and extraction times on the yield of DHEA.Based on this,the response surface test was designed to optimize the fermentation process conditions of Aspergillus oryzae,and the differences in the yield of DHEA under different extraction methods were compared and analyzed.Results showed that fermentation temperature,inoculation amount,fermentation time,fermentation solid-liquid ratio,peptone addition,and extraction times had significant impacts on the yield of DHEA.Through the regression model analysis predicted by response surface method,the optimum fermentation conditions of Aspergillus oryzae can be predicted as follows: inoculation amount 6%,fermentation time 72 h,fermentation temperature 30°C,fermentation solid-liquid ratio 1:15(g/m L).The theoretical value of the yield of DHEA is 97.07 ?g/100 g,and the result of the verification test was 94.70 ?g/100 g,which was not significantly different from the theoretical value.The results showed that the relative effects of each factor on the the yield of DHEA were as follows: inoculation amount > fermentation temperature >fermentation solid-liquid ratio > fermentation time.Using sweet potato as raw material,the yield of DHEA extracted by Aspergillus oryzae fermentation was significantly higher than that of pre-fermentation-acid hydrolysis,enzymatic hydrolysis and direct extraction without fermentation(p<0.05).(3)The basic components(dry matter,protein,fat,ash,starch,reducing sugar)and the content of DHEA in potato peel and pulp of 19 different varieties of sweet potatoes from four types,including starch type,purple potato type,high carotene type,and fresh food type,were compared and analyzed.Results showed there were extremely significant differences in the contents of the basic components among different varieties(P<0.01),but there was no significant difference in the content of the basic components among the four types(p>0.05);The DHEA content of the potato peel and pulp between the varieties had a very significant difference(P<0.01).The DHEA content of 19 sweet potato varieties was between 0-443.56 ?g/100 g,Luozi No.4 had the highest content,and the DHEA content of 19 sweet potato varieties was between 0-3084.17 ?g/100 g,Ningzi 8 had the highest content;The DHEA content in the pulp of the four types of sweet potatoes was significantly different(P<0.01),and the DHEA content in the pulp of the purple sweet potato was significantly higher than that of the other three.There was no significant difference in the DHEA content in the peel of the four types of sweet potatoes(p>0.05);The DHEA content in the pulp of Xiangshu 99,Sushu 36,Zhe 70,Luozi 4 was higher than that of the peel;Sushu 32,Jinong 51,Eshu 11,Xiang 203,Xushu 22,Luoshu 10,Q7007,Yushu 15,Wanshu 10,Zhe 71847,Ningzi 8 and other varieties of pulps have DHEA content lower than potato peel.The DHEA content in pulp of varieties such as Sushu 32,Jinong 51,Eshu 11,Xiang 203,Xushu 22,Luoshu 10,Q7007,Yushu 15,Wanshu 10,Zhejiang 71847,Ningzi 8 were lower than potato peel.(4)The antioxidant activity,anti-aging,hypoglycemic and anti-cancer effects of DHEA extract in sweet potato were preliminarily discussed.The results showed that sweet potato DHEA extract had good antioxidant activity before and after purification,and had a very significant positive correlation with the concentration(P<0.01);Sweet potato DHEA extract had a certain anti-aging and hypoglycemic effect before and after purification.The ?-amylase activity inhibition rate of the purified DHEA extract was between 2.16%-55.54%,and the tyrosinase activity inhibition rate was between5.55%-50.57%;In addition to the total reducing power,the antioxidant capacity of the DHEA extract DPPH,ABTS,and hydroxyl radical system before purification was higher than that after purification.It may be because the crude extract contained other antioxidant active substances that were lost during the purification process;The purified sweet potato DHEA extract had a significant inhibitory effect(p<0.05)on the proliferation of breast cancer cell MCF-7 when the concentration was 2.3 m M,and the inhibitory rate reached 47.5%.It had no inhibitory effect on lung cancer cell A549 and cervical cancer cell Hela. |
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