Three new protease inhibitors, planktopeptin BL1125, planktopeptin BL843 and planktopeptin BL1061 were isolated, along with three known compounds, anabaenopeptin A, anabaenopeptin B and anabaenopeptin F from the hydrophilic extract of Planktothrix rubescens. The planar structure of the new compounds was determined by homonuclear and inverse-heteronuclear 2D NMR techniques as well as high-resolution mass spectrometry. The absolute configuration of the asymmetric centers was studied using Marfey's method for HPLC and by comparison of the acid hydrolysate with authentic samples on a chiral HPLC column. The new peptides were found to be elastase and chymotrypsin inhibitors.
- Natural products
- Protease inhibitors