Antiplasmodial activity of sesquiterpene lactones and a sucrose ester from Vernonia guineensis Benth. (Asteraceae)

Ethnopharmacological relevanceAqueous preparations of Vernonia guineensis Benth. (Asteraceae) are used in Cameroonian folk medicine as a general stimulant and to treat various illnesses and conditions including malaria, bacterial infections and helminthic infestations.Materials and methodsTen gram samples of the leaf and tuber powders of Vernonia guineensis were extracted separately using dichloromethane, methanol and distilled water. The extracts were dried in vacuo and used in bioassays. These extracts and three compounds previously isolated from Vernonia guineensis [vernopicrin (1), vernomelitensin (2) and pentaisovalerylsucrose (3)] were screened for antiplasmodial activity against chloroquine (CQ)-sensitive (Hb3) and CQ-resistant (Dd2) Plasmodium falciparum lines.ResultsCrude extracts and pure compounds from Vernonia guineensis showed antiplasmodial activity against both Hb3 and Dd2. The IC50 values of extracts ranged from 1.64 to 27.2 µg/ml for Hb3 and 1.82–30.0 µg/ml for Dd2; those for compounds 1, 2 and 3 ranged from 0.47 to 1.62 µg/ml (1364–1774 nM) for Hb3 and 0.57–1.50 µg/ml (1644–2332 nM) for Dd2. None of the crude extracts or pure compounds was observed to exert toxic effects on the erythrocytes used to cultivate the Plasmodium falciparum lines.ConclusionIn Cameroonian folk medicine, Vernonia guineensis may be used to treat malaria in part due to the antiplasmodial activity of sesquiterpene lactones (1, 2), a sucrose ester (3) and perhaps other compounds present in crude plant extracts. Exploring the safety and antiplasmodial efficacy of these compounds in vivo requires further study.

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