Study On The Enzymatic Preparation Of Corn Germ Large Molecular Peptides Based On Ultrasonic Pretreatment And Its Antihypertensive And Immunoregulatory Activity

Defatted corn germ is a high nutritive substance based on protein and sugar.The protein contains a full range of amino acid with balanced composition,and is a good source of preparation of active peptides.Corn germ peptide prepared by enzymolysis has many kinds of active functions.The peptide is a mixture of oligopeptides,easy to be digested by the gastrointestinal tract,or even directly absorbed without digestion,neglecting the function of protease in healthy gastrointestinal tract.Ultrasound assisted enzymatic hydrolysis can make up for shortcomings of traditional enzymatic hydrolysis,and has been widely applied to peptide preparation.Nevertheless,there is a mode single problem in ultrasound pretreatment owing to backward test conditions.In this study,the large molecular peptides that could use protease from gastrointestinal tract,were prepared based on ultrasound assisted enzymatic hydrolysis.The effect of corn germ large molecular peptides on blood pressure of spontaneously hypertensive rat?SHR?was studied.And,the effect of corn germ large molecular peptides on immunoregulation of ICR mice was studied.The main conclusions drawn by the research are as following:Defatted corn germ was pretreated under three kinds of ultrasonic equipment,and hydrolyzed by alcalase.The enzymatic hydrolysates were digested in vitro.Angiotensin converting enzyme?ACE?inhibitory activity of gastrointestinal digestive hydrolysate and degree of hydrolysis?DH?of corn germ in enzymatic hydrolysis process were taken as the indexes for searching for the optimal ultrasonic working mode,ultrasonic pretreatment parameters and enzymolysis parameters.The results showed that best ultrasonic working mode was 20-40 kHz dual-frequency ultrasound,best power density was 120 W/L,best ultrasound pretreatment time was 15 min,best ultrasonic initial temperature was 30°C,best substrate concentration was 50 g/L,best enzyme dosage was 3000 U/g,best enzymolysis time was 30 min,best pH was 9.0and best enzymolysis temperature was 50°C.Under the optimal preparation conditions,the ACE inhibitory activity of enzymatic hydrolysates and gastrointestinal digestive hydrolysate was higher than control significantly.And the ACE inhibitory activity was 60.25%and 66.58%,respectively.And IC₅₀ was 4.166 mg/m L and 3.986mg/m L,respectively.The component of the molecular weight greater than 2000 Da was 36.56%.The antihypertension effect of defatted corn germ large molecular peptides on SHR was studied.The changes of blood pressure after single gavage test and long-term gavage test were determined.The changes of tissue ACE activity and serum biochemical indexes after long-term gavage test were determined.The results showed that defatted corn germ large molecular peptides could reduce the systolic and diastolic blood pressure of SHR after single gavage test,the maximum decline was16.89 mm Hg and 6.46 mmHg respectively.And the speed of blood pressure change was slower than captopril group.Defatted corn germ large molecular peptides could reduce the systolic and diastolic blood pressure of SHR after long-term gavage test,the maximum decline was 18.94 mmHg and 11.90 mmHg respectively.After four weeks of continuous gavage,the blood pressure of SHR could be maintained at a relatively low level.The lowering of blood pressure had a dose effect.The large molecular peptides could inhibit ACE activity in lung,kidney and heart,the decrease rate of ACE activity was 24.53%,22.28%and 12.93%.Serum index showed that the large molecular peptides conduct antihypertension effect mainly through descending content of Renin,ANG II,ET-1 and ascending content of NO,which were antihypertension-related serum index.The immunoregulation effect of defatted corn germ large molecular peptides on ICR mice was studied.The index of immune organ,the proliferation of immune cell and the content of serum immune factor were determined.The results showed that the defatted corn germ large molecular peptides had no effect on immune organs and T lymphocytes.The large molecular peptides could enhance immunoregulation function of monocyte macrophage and B lymphocyte,the increment of phagocytic index and antibody accumulation was 2.07 and 18.62 respectively.Serum index showed that the enzymatic hydrolysates conduct immunoregulation effect mainly through descending content of Renin,NO,IFN-?,IgG and C3,which were immunoregulation-related serum index.