Diabetes melitus ditandai dengan kadar gula darah yang melebihi normal (hiperglikemia) sebagai akibat dari tubuh yang kekurangan insulin relatif maupun absolut. Enzim α-glukosidase menghidrolisis karbohidrat menjadi glukosa. Pada pasien diabetes, penghambatan terhadap enzim α-glukosidase menyebabkan peghambatan terhadap absorbsi glukosa dan menurunkan hiperglikemia.Tujuan penelitian ini untuk mengetahui aktivitas penghambatan enzim α-glukosidase dari beberapa tanaman obat yang digunakan di Indonesia. Serbuk simplisia diekstrak dengan cara refluks menggunakan pelarut etanol 80%. Aktivitas penghambatan enzim α-glukosidase dilakukan dengan mengukur serapannya secara spektrofotometri. Akarbose digunakan sebagai standar. Penghambatan enzim α-glukosidase paling besar ditunjukkan pada ekstrak biji Swietenia mahagoni dengan nilai IC50 7,03 ppm diikuti oleh ekstrak daun Anacardium occidentale, biji Luffa cylindrical, umbi Dioscorea hispida, daun Blumea balsamifera, daun Catharanthus roseus, Allium cepa, daun Physalis angulata, herba Ocinum americanum dan daun Tectona grandis dengan nilai IC50 9,11 ppm; 17,46 ppm; 26,05 ppm; 28,01 ppm; 36,08 ppm; 50,58 ppm; 55,89 ppm; 80,78 ppm; dan 87,38 ppm. Ekstrak biji Swietenia mahagoni menunjukkan aktivitas penghambatan kompetitif. Hasil penapisan fitokimia menunjukkan semua ekstrak mengandung saponin dan glikosida.

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Diabetes mellitus is characterized by exceed blood sugar level to normal (hyperglycemia) caused by a relative or absolute deficiency in insulin. α-Glucosidase hydrolyzes carbohydrates into glucose. In diabetic patients, inhibition of this enzymes causes the restraint of glucose absorption and decreases the postprandial hyperglycemia.The purpose of this research was to evaluate the inhibitory activity of α-glucosidase in some medicinal plants used as antidiabetic in Indonesia. Crude drug powder was extracted by reflux using 80% ethanol. Inhibitory activity of α-glucosidase was evaluated by measuring the absorbance with spectrophotometry. Acarbose used as a standard. The biggest inhibitory activity of α-glucosidase demonstrated in Swietenia mahagoni seed extract with IC50 value of 7.03 ppm followed by Anacardium occidentale leaf, Luffa cylindrical seed, Dioscorea hispida root, Blumea balsamifera leaf, Catharanthus roseus leaf, Allium cepa, Physalis angulata leaf, Ocinum americanum leaf, and Tectona grandis leaf extracts with IC50 value of 9.11 ppm, 17.46 ppm, 26.05 ppm, 28.01 ppm, 36.08 ppm, 50.58 ppm, 55.89 ppm, 80.78 ppm, and 87.38 ppm. Swietenia mahagoni seed extract shown to be a competitive inhibitor. The result of phytochemical screening showed that all of the extracts contain saponin and glycoside.