A composition for inhibiting α-glucosidase has lower side effects to a user, other than the inhibition of α-glucosidase. The composition comprises adenine, (3-hydroxy-dl-proline, nicotinic acid, (3,6-dioxo-piperazin-2-yl)-acetic acid amide, 2-ethylhexyl heptanoate, and a pharmaceutically compatible salt.