Cinnamic acid as one of the antidiabetic active principle(s) from the seeds of Syzygium alternifolium

► Syzygium alternifolium (SA) distributed in the South Eastern Ghats of India. ► Antidiabetic active fraction (C2) was isolated from aqueous extract of SA seeds. ► LC-MS analysis of fraction C2 revealed the presence of three compounds. ► Cinnamic acid as one of the compound in fraction C2 is proved by TLC and HPLC. ► Fraction C2 effect on carbohydrate metabolic enzymes was studied in diabetic rats.