LONDON (AFP) - No plant toxins were found in the system of a Russian whistleblower who died aged 44 while jogging, a botanist told a London court examining his death, British media reported on Tuesday (April 10).

Alexander Perepilichny died near the British capital in 2012 and, two years later, his life insurance company ordered tests that detected a toxin in his stomach from a Chinese plant called Gelsemium, which can trigger cardiac arrest.

But during an inquest examining the cause of Perepilichny's death, a leading botanist cast doubt on the theory he had been poisoned.

Monique Symmonds, from the Royal Botanic Gardens in Kew, told the Old Bailey court that she had not been able to identify any plant toxins, the BBC and Financial Times reported.

Perepilichny, a wealthy businessman, had been helping investment firm Hermitage Capital Management investigate a money-laundering operation when he was found dead near his home in Weybridge, outside London.

His lawyer at the time, Dmitry Lipkin, told the court his client "did not come to Russia because he was fearful for his life".

"He was threatened. He left Russia but who he was threatened by, I don't know," he told the court via video-link from Moscow.

The case has come under increased scrutiny following last month's nerve agent attack on former Russian spy Sergei Skripal and his daughter Yulia in the English city of Salisbury.

Britain has blamed Russia for the attack - a charge vehemently denied by Moscow.

Following the Skripal poisoning, MPs have called on the government to re-examine 14 unexplained deaths on British soil in recent years, including that of Perepilichny, a Russian oligarch and a British spy found in a bag.

Lipkin said he had been working with Perepilichny on some debts that he owed in Russia.

"Alexander asked us to deal with a few matters, mostly those matters were concerning his debts," Lipkin said.

Asked if any of the debts were to organised crime figures, Lipkin replied: "I'm not aware of that."

The inquest is expected to last four days, with a verdict not expected immediately.