Interestingly, in an attempt to explore natural ACE inhibitors for hypertension treatment, we surprisingly found that karnamicins isolated from wild-type and mutant strains had significant ACE inhibitory activity with IC50 (the concentration yielding 50% inhibition) values ranging from 0.24 to 5.81 μM (except compound 32, Table 1). The gene discussed is ACE; the disease is Hypertension.