The widow of Russian whistleblower Alexander Perepilichny told an inquest on Monday that she did not believe her husband had been murdered and said she had cooked him a bowl of sorrel soup just before his sudden death.

Perepilichny, 44, had been out jogging when he collapsed and died in November 2012 outside the family home in Weybridge, Surrey, which he shared with his wife Tatiana and their two children.

Surrey police say his death is not suspicious. However, a pre-inquest hearing heard that traces of a rare and deadly plant poison, Gelsemium elegans, were discovered in his stomach and that the poison has been used in the past by Russian and Chinese assassins.

Giving evidence at the Old Bailey, Tatiana Perepilichnaya said her husband - who she called Sasha - had returned from a business trip to Paris. She said she had texted him asking him to bring some cream for a home-made soup she was preparing.

He texted back to say he was already home. The soup – made from a traditional Ukrainian recipe and called s’chee – had a naturally “sour” taste, she said. She said she was unable to recall where she had bought the sorrel, which came in a medium-sized glass jar.

She said she only ate a small amount of the soup at the time, adding that she and her daughter finished it later. When her husband failed to return from his run, she texted: “Where are you?”, the inquest heard. A passerby found his body not far from the couple’s rented mansion on the St George’s estate.

There was evidence that Perepilichnyy, who moved from Moscow to London with his family in 2010, was receiving threats from Moscow, the inquest heard. In the final months of his life, he took out insurance policies worth £3.5m and applied for another worth £5m.

Perepilichnaya, however, said there was nothing to suggest her husband was being threatened. She said he behaved normally, travelled by minicab and public transport and insured his life for a huge sum because they were about to buy a luxury property.

According to previous hearings, Perepilichny had received death threats, with his name also featuring on a hit list. The threats came after he revealed details of a $230m (£160m) fraud carried out by a Russian gang with alleged links to the Kremlin.

The money was stolen from taxes paid by the investment company Hermitage Capital to the Russian treasury. A lawyer who investigated the case, Sergei Magnitsky, was arrested and died in prison in 2009.

Perepilichnaya said she had no knowledge of her husband’s financial affairs or whether he had given documents to Hermitage and to Swiss prosecutors.

She said her husband was a deeply “private person” who loved teaching their children maths and physics. He struggled with his weight sometimes but was otherwise in good shape and had not complained of feeling ill before he dropped dead, she said.

Robert Moxon-Brown QC, acting for the insurer Legal & General, said that Perepilichny had engaged in money laundering for wealthy clients in Russia. They included Vladlen Stepanov, the husband of a senior Moscow tax official allegedly involved in the fraud. Money was sent offshore.

Asked if she knew about this, Perepilichnaya replied: “Of course not.”

The Old Bailey was told that Perepilichnyy had done business with Tatiana’s brother Rishat Ismagilov. Ismagilov, who lives in Moscow, had come under pressure from the police or authorities after Perepilichny fell out with his clients and decamped to a gated community in Surrey, the inquest heard.

Perepilichnaya said she knew nothing of this. She struggled to remember details of what had happened in the traumatic aftermath of her husband’s death - or the “horror”, as she called it. She complained of harassment from journalists and said 99% of the stories written about the case were untrue.

The inquest heard that in 2010, after Perepilichny had gone to the UK, Moscow made inquiries via Interpol as to his whereabouts. In recent weeks, her brother had given a statement claiming that Bill Browder, the chief executive of Hermitage, was a criminal and a spy.

Browder, who is due to give evidence on Thursday, alleges that Perepilichny was killed as a reprisal for his whistleblowing activities, with Surrey police bungling the investigation and accidentally destroying much of the evidence, including the dead Russian’s stomach contents.

Perepilichnaya gave evidence in Russian from behind a screen. She complained repeatedly of feeling tired and said on multiple occasions: “I can’t remember.”

Henrietta Hill QC asked her if she was aware her brother’s accusations were identical to those levelled against Browder by the Kremlin. Asked if Ismagilov had links himself to the Russian state, Perepilichnaya replied: “I don’t think so. I don’t know.”

The inquest continues.