Abstract
Artemisinin is the active antimalarial compound obtained from the leaves of Artemisia annua L. Artemisinin, and its semi-synthetic derivatives, are the main drugs used to treat multi-drug-resistant Plasmodium falciparum (one of the human malaria parasite species). The in vitro susceptibility of P. falciparum K1 and 3d7 strains and field isolates from the state of Amazonas, Brazil, to A. annua infusions (5 g dry leaves in 1 L of boiling water) and the drug standards chloroquine, quinine and artemisinin were evaluated. The A. annua used was cultivated in three Amazon ecosystems (várzea, terra preta de índio and terra firme) and in the city of Paulínia, state of São Paulo, Brazil. Artemisinin levels in the A. annua leaves used were 0.90-1.13% (m/m). The concentration of artemisinin in the infusions was 40-46 mg/L. Field P. falciparum isolates were resistant to chloroquine and sensitive to quinine and artemisinin. The average 50% inhibition concentration values for A. annua infusions against field isolates were 0.11-0.14 μL/mL (these infusions exhibited artemisinin concentrations of 4.7-5.6 ng/mL) and were active in vitro against P. falciparum due to their artemisinin concentration. No synergistic effect was observed for artemisinin in the infusions.
Highlights
Malaria is an infectious disease that affects millions of people in tropical and sub-tropical regions of the world
Traditional knowledge of the usefulness of medicinal plants has led to the isolation and identification of the antimalarial compounds quinine and artemisinin, which are currently in use and which are isolated from species of Cinchona L. (Rubiaceae) and the leaves of Artemisia annua L. (Asteraceae), respectively (Vale et al 2005)
The dried leaves of A. annua hybrids cultivated in the várzea, terra preta de índio and terra firme Amazonian ecosystems exhibited high levels of the antimalarial natural product artemisinin
Summary
The dried leaves of A. annua hybrids cultivated in the várzea, terra preta de índio and terra firme Amazonian ecosystems exhibited high levels of the antimalarial natural product artemisinin. The dry leaves of the standardised plant cultivated in Paulínia exhibited artemisinin levels of 1.13 ± 0.05%. The concentration of artemisinin in infusions of leaves of cultivated A. annua ranged from 40-46 mg/L (Table I). Standardised A. annua cultivated in Paulínia exhibited higher levels of artemisinin in its leaves and in its leaf infusions. The efficiency of artemisinin extraction by the infusion of leaves in boiling water ranged from 78-91% for plants cultivated in terra preta de índio and terra firme plots. The drug sensitivity profiles of the nine P. falciparum field isolates were evaluated against the commercial drugs chloroquine, quinine and artemisinin through the determination of their IC50 values (Table II). The IC50 values obtained for artemisinin against Amazonian field isolates exhibited low variation (average IC50 = 2.1 ± 1.0 nM). Given the number of samples studied, the levels of sensitivity of Amazonian P. falciparum field isolates to artemisinin are in agreement with results for other field isolates reported
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