Possibly the best Guardian story of all time

It seems  that a Russian whistleblower may have been poisoned with a derivative of the obscure plant gelsemium elegans.  It turns out that an important paper on the poison was written by Sir Arthur Conan Doyle, years before he became a popular writer.

 

In a paper, published in a 1879 issue of the British Medical Journal, the author and physician describes self-experimenting with tinctures of gelsemium, to test its properties as a poison. He had become curious after using the tincture to treat nerve pain and, noticing that overstepping the advised dose appeared to have no ill-effects, decided to up his intake by a small amount each day.

 

After taking 9ml, Conan Doyle “suffered from severe frontal headache, with diarrhoea and general lassitude”. After 12ml – the highest dose he managed – he reported: “The diarrhoea was so persistent and prostrating, that I must stop at 200 minims [12ml]. I felt great depression and a severe frontal headache. The pulse was still normal, but weak.”

There may be few poisons unknown to science, but there are certainly poisons rare enough that a casual autopsy would miss them, as seems to have happened in this case.   (Also, it doesn't pay to piss off Vladimir Putin, but we all knew that.)  According to the Guardian, in "Asia" (vague enough for you?) the plant is known as "heartbreak grass", as in "want to retaliate for that heartbreak?  Have I got a tincture for you."