I think that it is common in a great many plants and that it's toxicity may contribute to the antiviral properties of sutherlandia frutescens. In the OPC supplement, only 20% of the extract is from s. frutescens - and s.frutescens has a long history of safe use in South Africa - where it is known as the South Africa Cancer Bush and is so highly regarded that a government postal stamp was issued in its honor.