A series of phenylethyl cinnamides, which included new compounds named anhydromarmeline, aegelinosides A and B, were isolated from Aegle marmelos leaves as alpha-glucosidase inhibitors. The structures of new compounds were characterized by spectroscopic data and chemical degradation. Of compounds isolated, anhydroaegeline revealed the most potent inhibitory effect against alpha-glucosidase with IC(50) value of 35.8 microM. The present result also supports ethnopharmacological use of A. marmelos as a remedy for diabetes mellitus.