Phytochemicals and antidiabetic activity of Eusideroxylon zwageri stem bark collected from East Kalimantan, Indonesia

Eusideroxylon zwagery (Lauraceae), a tropical tree species known as ulin or borneo iron wood and traditionally used for the treatment of diabetes in the Ethnic of Kutai. Plant extract was prepared by maceration using ethanol. The plant extract was evaluated its DPPH and superoxide radicals scavenging activity, the inhibition on alpha-glucosidase and alpha-amylase activity as antidiabetic potential and the analysis of the total phenolic, total flavonoids and proanthocyanidin contents. The ethanolic extract of the stem bark was 8.62% on the dry weight basis. The IC50 values of antioxidant activity of the extract in DPPH and superoxide radical scavenging mechanisms were 44.90 mu g/ml and 30.47 mu g/ml. In antidiabetic assay, the E. zwageri stem bark extract showed IC50 value 58.45 mu g/ml in alpha-glucosidase inhibition, and 9.04 mu g/ml in alpha-amylase inhibition. Quercetin, an antidiabetic activity-having flavonoid, displayed IC50 values 2.00 mu g/ml and 4.04 mu g/ml in alpha-glucosidase and alpha-amylase inhibitory assays. In phytochemical assay, the extract had 31.28 GAE/g extract (mg), 30.48 CE/g extract (mg) and 183.3 PE/g extract (mg) for the total phenolic, total flavonoid and total proanthocyanidin contents. The limited reports of E. zwageri indicated the needs to search the active compounds from plant as potential antidiabetic agents by considering plant conservation status.