New flavone and phenolic esters from Callistemon lanceolatus DC: Their molecular docking and antidiabetic activities

Phytochemical investigation of the antidiabetic chloroform fraction of the ethanolic extract obtained from the aerial parts of Callistemon lanceolatus DC led to the isolation of three new phytoconstituents, one flavone, 8-(1″-hydroxyisopranyl)-5,6-dihydroxy-7,4′-dimethoxy flavone (1) and two phenolic esters, 2,3,4-trihydroxyphenethyl tetracontanoate (2) and 2,3,4-trihydroxyphenethyl tetracontanoate-4-β-xylopyranoside (3). The isolated compound 1 exhibited significant in vivo blood glucose lowering effect comparable to the standard drugs Pioglitazone and Rosiglitazone in streptozotocin induced diabetic rats without causing any toxic effect on the pancreas and liver. Compound 1 showed a glide score of −7.89 against PPAR-γ target in molecular docking studies which is significantly higher than the glide score of reference molecule Rosiglitazone (glide score of −5.77). Compound 1 also exhibited moderate in vitro PPAR-γ transactivation activity of 48.52% in comparison with standard drugs rosiglitazone and pioglitazone, which showed a transactivation activity of 80.47% and 65.27%, respectively.