Since antiquity, Achillea millefolium L. (Asteraceae) has been used in traditional medicine of several cultures, from Europe to Asia. Its richness in bioactive compounds contributes to a wide range of medicinal properties. In this study, we assessed A. millefolium methanolic extract and its isolated components for free radical scavenging activity against 2,2-diphenyl-pycrilhydrazyl, total antioxidant capacity (based on the reduction of Cu(++) to Cu(+)), and ability to inhibit lipid peroxidation. The activity against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum was also tested. Chlorogenic acid, its derivatives and some flavonoids isolated by semipreparative HPLC and identified by NMR and spectrometric techniques were the major bioactive constituents of the methanolic extract. The latter exhibited significant antioxidant properties, as well as its flavonol glycosides and chlorogenic acids. With regard to the antiplasmodial activity, apigenin 7-glucoside was the most effective compound, followed by luteolin 7-glucoside, whereas chlorogenic acids were completely inactive. On the whole, our results confirmed A. millefolium as an important source of bioactive metabolites, justifying its pharmaceutical and ethnobotanical use.

Objectives Plasmodium gametocytes, responsible for malaria parasite transmission from humans to mosquitoes, represent a crucial target for new antimalarial drugs to achieve malaria elimination/eradication. We developed a novel colorimetric screening method for anti-gametocyte compounds based on the parasite lactate dehydrogenase (pLDH) assay, already standardized for asexual stages, to measure gametocyte viability and drug susceptibility. Methods Gametocytogenesis of 3D7 and NF54 Plasmodium falciparum strains was induced in vitro and asexual parasites were depleted with N-acetylglucosamine. Gametocytes were treated with dihydroartemisinin, epoxomicin, methylene blue, primaquine, puromycin or chloroquine in 96-well plates and the pLDH activity was evaluated using a modified Makler protocol. Mosquito infectivity was measured by the standard membrane feeding assay (SMFA). Results A linear correlation was found between gametocytaemia determined by Giemsa staining and pLDH activity. A concentration-dependent reduction in pLDH activity was observed after 72 h of drug treatment, whereas an additional 72 h of incubation without drugs was required to obtain complete inhibition of gametocyte viability. SMFA on treated and control gametocytes confirmed that a reduction in pLDH activity translates into reduced oocyst development in the mosquito vector. Conclusions The gametocyte pLDH assay is fast, easy to perform, cheap and reproducible and is suitable for screening novel transmission-blocking compounds, which does not require parasite transgenic lines.