Studies On The Chemical Constituents Of Polyphenols From The Root Of Astragalus Membranaceus Var. Mongholicus

Astragalus membranaceus var.mongholicus(AM),a perennial herb of the Leguminosae family,is mainly distributed in Shanxi,Inner Mongolia,Gansu,Hebei,and Heilongjiang of China.The root of AM was first recorded in “Shen Nong’s Herbal Classic”and listed top-grade item.The Chinese Pharmacopoeia(2015 edition)stipulates that Radix Astragalus is the dried root of Astragalus membranaceus var.mongholicus or Astragalus membranaceus,which has the effects of tonifying qi and raising yang.Recent pharmacological studies showed that it exhibited a series of biological activities,such as antidiabetic,hepatoprotective,anti-oxidation,and immunoregulatory effects.Previous studies demonstrated that polysaccharides,isoflavonoids,and triterpenoids were the major constituents in the root of A.membranaceus var.mongholicus.In the previous research of our team on the lipophilic small-molecular constituents of the root of A.membranaceus var.mongholicus,36 isoflavonoids and 15 triterpenoids were isolated,some of which showed antidiabetic and antiplatelet aggregation activity.In this study,16 compounds were isolated from fractions ASMEB and ASMEF using various chromatographic methods.These compounds were unambiguously determined by spectroscopic analyses(UV,IR,MS,and NMR)and chemical methods,including 9phenylpropanoids(1-9),3 isoflavones(10-12),2 isoflavanes(13 and 14),and 2pterocarpans(15 and 16).Compounds 1,2,3,9,10,and 15 were new compounds,and compound 8 was first obtained from the genus Astragalus.Notably,compound 10 was the rare case of isoflavanoids with the simultaneous oxidation at 2,4,5-positions of the B-ring.The α-glucosidase inhibitory assay was applied to evaluate the hypoglycemic activity of compounds 1-16.The result showed that all of these compounds exhibited different levels of hypoglycemic activity.Among them,compounds 10,12,and 14 exhibited the α-glucosidase inhibitory activity with potency close to that of the positive control(acarbose).These results are beneficial for understanding the scientific basic on the efficacy of the root of AM.