Ameliorative Effects of Flavonoids from Platycodon grandiflorus Aerial Parts on Alloxan-Induced Pancreatic Islet Damage in Zebrafish.

Platycodon grandiflorus (balloon flower), used as a food reserve as well as in traditional herbal medicine, is known for its multiple beneficial effects. In particular, this plant is widely used as a vegetable in Republic of Korea. We examined the ameliorative effects of P. grandiflorus on alloxan-induced pancreatic islet damage in zebrafish. The aerial part treatment led to a significant recovery in pancreatic islet size and glucose uptake. The efficacy of the aerial part was more potent than that of the root. Eight flavonoids ( 1 - 8 ) were isolated from the aerial part. Structures of two new flavone glycosides, designated dorajiside I ( 1 ) and II ( 2 ), were elucidated to be luteolin 7- O -α-L-rhamno-pyranosyl (1 → 2)-(6- O -acetyl)-β-D-glucopyranoside and apigenin 7- O -α-L-rhamnopyranosyl (1 → 2)-(6- O -acetyl)-β-D-glucopyranoside, respectively, by spectroscopic analysis. Compounds 1 , 3 , 4 and 6 - 8 yielded the recovery of injured pancreatic islets in zebrafish. Among them, compound 7 blocked K ATP channels in pancreatic β-cells. Furthermore, compounds 3 , 4 , 6 and 7 showed significant changes with respect to the mRNA expression of GCK , GCKR , GLIS3 and CDKN2B compared to alloxan-induced zebrafish. In conclusion, the aerial part of P. grandiflorus and its constituents conferred a regenerative effect on injured pancreatic islets.