Chemical variation and artemisinin content of A. afra and A. annua

As part of our ongoing crowd funding campaign to investigate whether Artemisia might become a useful treatment of Covid 19, we continue with the chemistry of these two species (if you have a dollar to spare please donate on the crowd funding website). Tea infusions (as described earlier) of three A. afra samples (collected here in Potch and Bronkhorstspruit, South Africa) and 3 A. annua samples (A3 variety grown in Germany and harvested in different years) were prepared. If all goes well, we will also be testing these samples against SARS-CoV-2. Results from Germany, from a different research group, indicated that extracts of A. annua does indeed show activity against the virus, whereas artemisinin was found to be inactive. So it is good news, but there is still a lot to do. With their permission I will upload the link to those results.  

In this study all six samples were analysed with our UPLC system using the same method and settings that was used for the stability tests. I have also developed a very sensitive MRM method for the quantification of artemisinin on our LCMS with a sensitivity level of about 1 – or so picogram (on column). Still need to do all the calculations, so at the moment it is only a qualitative result. Now, A. afra is quite interesting because I could never find any trace of artemisinin in any of the samples that I’ve analysed over the years. The main idea behind looking for artemisinin in A. afra is that it grows very well in the sub-Saharan Africa region, so finding a individual plant that produces artemisinin might eventually produce a better growing and higher yielding variety (after plant breeding of course) than A. annua (which is from China). There is a global shortage of artemisinin, and the world needs a lot more in order to fight malaria effectively.  

So first up, the 3 A. afra samples (Fig 1) 

 

3X Afra comparison
Fig. 1: Overlaid chromatograms of tea infusions prepared from 3 different A. afra samples. 

This is quite lovely. Many similarities, but also big differences in concentrations and some chemical differences. It might be a bit difficult to see but look at the peak near 20min. Sample 1 does not contain this compound at any appreciable level whilst the other 2 have high levels of this compound. Lets say for example that we find sample 1 inactive, sample 2 reasonably active and sample 3 by far the most active, then it would be quite possible that the main active compound is this peak at 20min. If this is the case we can isolate, identify and test the purified compound against the virus in order to confirm this. So it can all be quite easy, but from experience I can tell you, it rarely is. But lets stay positive, and fist test against the virus.

Figure 2 illustrates the A. annua samples. Same story applies.

3X Annua comparison
Fig. 2: Overlaid chromatograms of tea infusions prepared from 3 different A. annua samples. 

Artemisinin content

In short, large quantities in all three A. annua samples and not even a trace in any of the  three A. afra samples – as expected (I also injected 10X more of the A. afra samples than the A. annua samples). However, analysing a different A. afra sample which was used in two clinical trails (malaria and schistosomiasis) I did find relatively large quantities of artemisinin (this is also reported in their publications). Now, how can this be? According to the authors, this particular A. afra sample was bought at Kirstenbosch, Cape Town and it was germinated and grown close to A. annua in Senegal. It might be that this particular A. afra specimen is our missing link and it do indeed contain artemisinin, but I don’t know. According to two of the authors, hybridization between the two species is unlikely. Another possibility is that A. afra were contaminated by the pollen of A. annua plants which was grown nearby, or it might even be something simple as using a ‘dirty’ grinder.

Point is, I am not convinced that this is my missing link so and I am still ‘fighting’ with the authors about this issue. We’ll eventually figure it out.

Forthcoming attractions: Sending those samples to be tested against the virus, fractionation of samples (just did not get the time this week), accurately quantifying artemisinin, and winning my ‘fight’ with the authors of the clinical trials.

 

One thought on “Chemical variation and artemisinin content of A. afra and A. annua”

  1. This is good , I have learnt a lot of things here, we hope to have a world free of malaria . We keep the faith

    Like

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