New DNA tests are being carried out to discover what a Russian whistleblower might have consumed before he died in a suspected poisoning - but the results have yet to be revealed, an inquest heard.
Alexander Perepilichnyy, 44, was helping specialist investment firm Hermitage Capital Management uncover a 230 million US dollar (£150 million) Russian money-laundering operation before his death.
An inquest at the Old Bailey is examining whether he died of natural causes or was poisoned, and if so, who had a motive for his murder.
Mr Perepilichnyy had eaten sorrel soup prepared by his wife on the day he collapsed while out jogging near his home in Weybridge, Surrey, in November 2012, the inquest has heard.
Renowned Kew botanist Professor Monique Simmonds told the inquest her expertise is in identifying plant toxins and compounds.
She said she had begun DNA testing on Mr Perepilichnyy's stomach contents, including the components of the sorrel soup.
Prof Simmonds said: "We are hoping that we will get some results possibly in a fortnight."
She said they were looking for potential toxins that would act in a few hours.
Kew has compiled a database of natural poisons, including plants, fungi, algae, frogs and snakes as well as other components, she said.
A team at Kew Gardens identified an unknown compound with potential links to gelsemium, a toxic plant, the inquest heard.
In common with nearly 5,000 other substances, it shared the same molecular weight.
However, further examination of its composition ruled gelsemium out and the identity of the material remained a mystery.
Among the compounds with the same weight were five variants of gelsemium and one of scolpolia, the nightshade plant famously used by Dr Crippen to kill his wife.