Antiprotozoal 6-substituted-5,6-dihydro-alpha-pyrones from Raimondia cf. monoica.

Dichloromethane extracts of both the roots and the leaves of Raimondia cf. monoica showed in vitro antiplasmodial and leishmanicidal activities against Plasmodium falciparum and Leishmania panamensis, respectively. Three 6-substituted 5,6-dihydro-2H-pyran-2-ones were isolated. (1) and (2) were identified as (6S)-(5'-oxohepten-1'E,3'E-dienyl)-5,6-dihydro-2H-pyran-2-one (1) and (6R)-(5'-oxohepten-1'Z,3'E-dienyl)-5,6-dihydro-2H-pyran-2-one (2), respectively. (-)-Arentilactone (3) was also isolated. The structure of the new compound (1) was determined by spectroscopic methods; additional spectroscopic data for (2) are reported for the first time.