Linear Peptides Containing d-Leucine with Neuroprotective Activities from the Leech Whitman.

Three new linear peptides containing d-leucine, named whitmantides A-C (-), were isolated from the dried whole bodies of Whitman. Their structures with absolute configurations were elucidated by Edman degradation, mass spectrometry, Marfey's analysis, and solid-phase synthesis. It is the first time that peptides containing d-amino acid in leeches were discovered. Compounds - displayed neuroprotective activities against oxygen-glucose deprivation/reperfusion injury on Neuro-2a cells. In addition, ex vivo serum stability tests showed that - were resistant to protease degradation.