Sweet potato (Ipomoea batatas (L.) Lam. 'Tainong 57') storage root mucilage was extracted (crude mucilage) and further purified by SDS and heating treatment (purified mucilage). Purified mucilage treated with 2-mercaptoethanol moved as a single band in SDS-PAGE. This purified mucilage was active to inhibit angiotensin converting enzyme (ACE) as shown by spectrophotometric method in a dose-dependent manner (28.7 to 59.8% ACE inhibition, respectively, by 50 to 400 mu g/mL mucilage) using (N-(3-[2-furyl] acryloyl)-Phe-Gly-Gly) (FAPGG) as a substrate. The concentration of mucilage required for 50% inhibition (IC50) of ACE activity was 364.5 mu g/mL while that of captopril was 10 nM (8.68 mu g/mL). The commercial polysaccharide pectin (50 to 400 mu g/mL) showed no inhibitory activity against ACE. When using fluorescent silica TLC to detect FAPGG and FAP, the results also showed that mucilage inhibited ACE. The mucilage showed mixed type inhibition against ACE, and the Michaelis constant in the presence of mucilage was 12 mM. We suggest that consumption of sweet potato storage root mucilage may benefit people's health.
