Chemical Study On Microtoena Prainiana, Microtoena Insuaris And Steudnera Colocasiaefolia

In this work, the plants Microtoena prainiana Diels, Microtoena insuaris (Hance) Prain ex Dunn and Steudnera colocasiaefolia C. Koch were chemically studied.1. Four new compounds together with twenty known compounds were isolated from the 95% ethanol extracts of the stems of Microtoena prainiana Diels for the first time. Their structures were elucidated on the basis of spectral and chemical evidence. The new compounds isolated were determined as follows: cyclo-(Ala-Val~1-Pro~1-Tyr-Leu-Val~2-Pro~2-Phe) [microtoenin A], cyclo-(Phe~1-Phe~2-Val-Pro-Phe~3-Gly-Ala~1-Ala~2) [microtoenin B], cyclo-(Pro~1-Tyr-Asn-Phe-Pro~2-Leu-Pro~3-Ile) [microtoenin C] and 3"'-O-methylcrenatoside. At a concentration of 1.0 mg/mL, 3"'-O-methylcrenatoside, crenatoside and isocrenatoside inhibited angiotensin converting enzyme (ACE) activity by more than 99%.2. Eleven compounds were obtained from the 95% ethanol extracts of the stems of Microtoena insuaris (Hance) Prain ex Dunn for the first time. 7a, 18-dihydroxy-8 (14)-abietaene 9a, 13a-endoperoxide is a new compound.3. Eleven compounds were obtained from the 95% ethanol extracts of the tubers of Steudnera colocasiaefolia C. Koch for the first time.4. Natural products possessing ACE inhibitory activity reported between1980-2003 were summarized.