Alkaloids from <i>Stephania cephalantha</i> and their enzyme inhibitory activities

A new protoberberine type alkaloid, 11-diethylaminomethyl corydalmine (<b>1</b>), and 27 known alkaloids (<b>2</b>-<b>28</b>) were isolated from the tuberous roots of <i>Stephania cephalantha</i>. Their structures were identified by spectral analysis. Enzyme inhibitory activities of the compounds on acetylcholinesterase (AChE), tyrosinase and α-glucosidase were evaluated. Compounds <b>13</b>, <b>16</b> and <b>18</b> exhibited comparable AChE inhibitory activities to the positive control huperzine A, with the IC₅₀ values of 0.046, 0.048, and 0.057 mg/mL, respectively.