Rhubard is a underrated plant which grows all around the world. Rhubarb have wide leaves and long stems. It is used along with many dishes as an enhancement, also used as dye and for medicinal purposes.
Leaves of rhubarb contain large amounts of oxalic acids which cause many diseases and even fatality. Bloody urine, vomiting, tremors, diarrhea is the common signs that seen by the consumption of rhubarb leaves. But it’ stem is out of toxic elements can can be used for making different dishes.
Rhubarb leaves contain poisonous substances, including oxalic acid, which is a nephrotoxic and corrosive acid that is present in many plants. Humans have been poisoned after ingesting the leaves, a particular problem during World War I when the leaves were mistakenly recommended as a food source in Britain.
The toxic rhubarb leaves have been used in flavoring extracts, after the oxalic acid is removed by treatment with precipitated chalk. Oxalic acid can also be found in the stalks of rhubarb, but the levels are too low to cause any bodily harm.
The LD50 (median lethal dose) for pure oxalic acid in rats is about 375 mg/kg body weight, or about 25 grams for a 65-kilogram (143 lb) human. Other sources give a much higher oral LDLo (lowest published lethal dose) of 600 mg/kg. While the oxalic acid content of rhubarb leaves can vary, a typical value is about 0.5%, so a rather unlikely 5 kg (for a 70 kg human) of the extremely sour leaves would have to be consumed to reach the LD50 of oxalic acid. Cooking the leaves with soda can make them more poisonous by producing soluble oxalates. However, the leaves are believed to also contain an additional, unidentified toxin, which might be an anthraquinone glycoside (also known as senna glycosides).