Isocrenatoside (compound 6) is a cyclic octapeptide and an inhibitor of angiotensin-converting enzyme (ACE). Isocrenatoside is isolated from the ethanolic extract of Microtoena prainiana stems. Studies have found that the inhibitory efficiency of 1 mg/mL Isocrenatoside can reach 99.3%.
References:
[1]. Li CQ, et al. Three cyclooctapeptides and one glycoside from Microtoena prainiana. J Nat Prod. 2004 Jun;67(6):978-82.