Artemisia annua hot water infusion (tea) has been used in in vitro experiments against P. falciparum malaria parasites to test potency relative to equivalent pure artemisinin. High performance liquid chromatography (HPLC) and mass spectrometric analyses were employed to determine the metabolite profile of tea including the concentrations of artemisinin (47.5±0.8 mg L-1), dihydroartemisinic acid (70.0±0.3 mg L-1), arteannuin B (1.3±0.0 mg L-1), isovitexin (105.0±7.2 mg L-1) and a range of polyphenolic acids. The tea extract, purified compounds from the extract, and the combination of artemisinin with the purified compounds were tested against chloroquine sensitive and chloroquine resistant strains of P. falciparum using the DNA-intercalative SYBR Green I assay. The results of these in vitro tests and of isobologram analyses of combination effects showed mild to strong antagonistic interactions between artemisinin and the compounds (9-epi-artemisinin and artemisitene) extracted from A. annua with significant (IC50 <1 μM) anti-plasmodial activities for the combination range evaluated. Mono-caffeoylquinic acids, tri-caffeoylquinic acid, artemisinic acid and arteannuin B showed additive interaction while rosmarinic acid showed synergistic interaction with artemisinin in the chloroquine sensitive strain at a combination ratio of 1:3 (artemisinin to purified compound). In the chloroquine resistant parasite, using the same ratio, these compounds strongly antagonised artemisinin anti-plasmodial activity with the exception of arteannuin B, which was synergistic. This result would suggest a mechanism targeting parasite resistance defenses for arteannuin B’s potentiation of artemisinin.

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In parts of Africa and Asia, self-medication with a hot water infusion of Artemisia annua (Artemisia tea) is a common practice for a number of ailments including malaria and cancer. In our earlier work, such an extract showed better potency than artemisinin alone against both chloroquine-sensitive and -resistant parasites. In this study, in vitro tests of the infusion in MCF7 cells showed high IC50 values (>200 μm). The combination of artemisinin and 3-caffeoylquinic acid (3CA), two major components in the extract, was strongly antagonistic and gave a near total loss of cytotoxicity for artemisinin. We observed that the interaction of 3CAs with another cytotoxic compound, cisplatin, showed potentiation of activity by 2.5-fold. The chelation of cellular iron by 3CA is hypothesized as a possible explanation for the loss of artemisinin activity.

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The DNA sequence of a cloned segment of the Escherichia coli chromosome containingftsQ,ftsA, and part of the ftsZ gene was determined and interpreted for genetic complementation and promoter fusion data for the region. The contiguous genes ftsQ, ftsA, and ftsZ were transcribed in the same direction (clockwise on the genetic map) and each had at least one associated promoter which allowed it to be transcribed independently of neighboring genes. ftsA and ftsZ possessed promoters within the coding sequences of the juxtaposed upstream structural genes, and a promoter element for ftsA was surrounded by a region of twofold symmetry which corresponded closely to a symmetrical element in the region of a putativeftsZ promoter. The structural gene of ftsQ consisted of 838 nucleotides, encoding a 276-residue amino acid polypeptide of molecular weight 31,400; the structural gene of ftsA consisted of 1,260 nucleotides, encoding a 420-residue amino acid polypeptide of molecular weight 45,400. The observation that the termination codon offtsQ overlaps with a potential initiation codon for ftsA suggested that these two genes may be translationally coupled when transcription is initiated upstream of the ftsQ coding sequence.