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Purple sweet potato (Ipomoea batatas var Ayumurasaki) has been reported as a component of daily diet for type 2 diabetes mellitus patient because of it has low glycemic index. A mechanism for decreasing blood’s sugar content in diabetic patients is by inhibiting α-glucosidase. In this study, the potencies of alkaloid fraction from leaves and anthocyanin fraction from tuberous of purple sweet potato were investigated as an inhibitor of α-glucosidase. The sample used was purple sweet potato from Ciampea, Bogor, West Jawa. The 2.0% alkaloid fraction could inhibit α-glucosidase activity (61.88%), whereas anthocyanin fraction was inactive (only inhibited 0.25%). The alkaloid fraction from purple sweet potato leaves was then fractionated by column chromatography with silica gel as stationary phase and chloroform as eluent. Fraction containing alkaloid with Dragendorf spraying was F10, which was further separated by preparative thin layers chromatography. F10.15 fraction contained alkaloid and had inhibition activity of 18.07% at concentration of 1.25%, which means separation decrease the activity of fraction. Fourier transform infrared spectrum of this fraction showed –NH−, –OH, and –CH2
– functional groups and was predicted as containing alkaloid.