Research On Hypoglycemic Activity And Mechanism Of Origanum Vulgare L.leaf Extract

Diabetes is a global chronic disease.With the gradual improvement of living standards,the incidence of diabetes is also increasing.Currently,clinically drugs for the treatment of diabetes are classified as biguanides,sulphonylureas,?-glucosidase inhibitors and et al,but they all produce a series of adverse reactions.At present,there are no drugs or methods for eradicating diabetes,so it is very important to find a low-toxic and effective functional food or drug for preventing and treating diabetes.Origanum vulgare L.is a traditional Chinese herbal medicine and fits the concept of"medicine food homology".The theory of traditional Chinese medicine believes that it has the effect of "clearing the heat and relieving the swelling".Origanum vulgare is known to be rich in phenolic acids,oregano glycosides,flavonoids,triterpene and sterols and other metabolites,and to show numerous beneficial biological activities,such as antibacterial,anti-oxidation,anti-melanin deposition,anti-cancer and other pharmacological effects.In our present study,under the guidance of activity screening in vitro,the main chemical components of extracts from Origanum vulgare.leaf was determined by HPLC and ESI-QTOF-MS.In addition,the hypoglycemic activity and its mechanism of the extract from Origanum vulgare leaf in October were discussed in the HepG2 cells and HepG2 GFP-CYP2E1(CYP2E1 expression of HepG2 cells,E47 cells)cell.The specific contents mainly included the following three aspects:1.The Origanum vulgare were collected during from April to October 2015.The dry Origanum vulgare leaves were extracted ultrasonic with acetonitrile-water(1:1),then it was freeze dried for later use.Its antioxidant activities at different harvesting stages was compared by the total antioxidant capacity(FRAP)and free radical scavenging capacity(ABTS).The results showed that the extract of Origanum vulgare leaves in July had better antioxidative capacity.On the other hand,a-glucosidase inhibition test and fluorescence glucose(2-NBDG)absorption test were applied for screening its hypoglycemic activity.The results showed that the extract of Origanum vulgare.leaves in October played the greater hypoglycemic activity.2.HPLC-ESI-QTOF-MS was used to identify the main chemical constituents of the extracts of Origanum vulgare leaves.The analysis identified Origanoside I?Luteolin 7-O-glucuronide?Apigenin 7-O-glucuronide?Rosmarinic acid?Lithospermic acid?Origanoside I derivative(unknown)as the main plant constituents.Moreover,the contents of total phenolics and total flavonoids were further determined.The results showed that the content of total phenols of Origanum vulgare leaves in July was the highest among the other extracts,while the content of total flavonoids of Origanum ivulgare leaves in September was highest.Combined with the results of the above antioxidant and hypoglycemic activities,it is speculated that the phenolic component may be the main antioxidant component,and the flavonoids and other constitutes may be the main hypoglycemic activity compounds.3.The hypoglycemic activity and mechanism of the Origanum vulgare leaves in October was assessed in HepG2 and E47 cell model.The results showed that Origanum vulgare leaves has a strong hypoglycemic activity to inhibit a-glucosidase,promote glucose uptake,and lower glycosylation levels,as well as to relieve the oxidative damage by reducing the level of oxygen free radicals(ROS)and the activity of lactate dehydrogenase(LDH).Molecular mechanism results also showed that the extract of Origanum vulgare leaves decreased the promoter activity and the mRNA and protein expression of PEPCK,which is a key promoter of gluconeogenesis,and also reduced the promoter activity and the mRNA and protein expression of SREBP-1c,which is the key lipid synthesis factor,as well as inhibited the expression of CPY2E1,then enhanced the expression of GLUT2,to exerted together its hypoglycemic effect.In summary,this study systematically studied the biological activity and the main components of Origanum vulgare leaves extract in different harvesting periods,and focused on its in vitro hypoglycemic activity and possible mechanism.It provides experimental basis for the comprehensive development and utilization of the medicine and food homology(Origanum vulgare),meanwhile Origanum vulgare may have a good potential to treat diabetes.