Are Murunga and Katurumuringa leaves toxic?
Dr Parakrama Waidyanatha
In an article titled ‘Throw more light on green foods’ that appeared in the Island of the 20th instant, Mr Gamini Peiris reports about an eminent doctor’s warning to his friend, who told the doctor that he regularly ate Katurumuringa or Sesbania grandiflora (Sg) leaves thrice a week, to stop eating it as it is toxic and so are Murunga(Drumstick) leaves! My family also eat Sg leaves once or twice a week, and hence sought information on the ‘toxicities’ of both species.
Both leaves and flowers of Sg are very commonly eaten. It is a common leguminous tree that grows to a height of about 6-8 meters, fixes nitrogen and native to South East Asia and Northern Australia. The leaves are commonly eaten in all growing countries and are reported to contain 25 to 30% crude protein. For this reason it is also widely used as a fodder for both cattle and goats, especially in India. Goat milk yield is reported to have increased by 25% with Sg leaf feeding. There is no evidence of leaf or flower material being toxic to humans and animals.
Muringa indica or Drumstick is native to parts of Africa and Asia. It is also cultivated in Central and South America, the Caribbean and South East Asia. India is reported to produce 1.2 million tons of pods per year from an area of 380 square kilometers. There are no reports of pods or leaves being toxic. Toxicity to humans being limited to certain compounds ( extracts) from the bark and roots, which are used in Aurvedic and other native medicines in addition to leaves and flowers. Both the pods and foliage are widely consumed in all countries where the crop is grown. For long term storage, dried leaves are powdered for preservation and are commonly added to sups sauces and smoothies. The leaves are rich in Vitamins A, B1, B2, B3, B5 , B6 and C. In Sri Lanka, the crop thrives in the dry and semi-arid areas, and Jaffna Peninsula is the largest producer of the crop.
The good specialist doctor should do well to know that in general there are toxic compounds in most fruits and vegetables we eat! For example, all solanacious plants such as tomatoes, brinjals and potatoes contain natural toxins, solanines and chaconines which are glycol-alkaloids but in low concentrations. These toxins are usually produced in response to stresses such as bruising, UV light, insect and other pest attacks. Wild mushrooms which are widely eaten especially by inhabitants in the growing regions, contain several toxins such as muscimol and muscarine which are reported to cause vomiting diarrhea, visual disturbances and hallucinations. Kernels within the pits of some stone fruits such as apricots, cherries, peaches, pears, plums and cherries contain cynogenic glucoside which can be converted to hydrogen cyanide, when consumed, which is highly poisonous. This toxin is also found in cassava(manioc) root and fresh bamboo shoots, necessitating that they are cooked before consumption.
The good specialist doctor should do well to remember the wise words of Bombastus Paracelsus(1591 – 1643), the father of the science of pharmacology, that ‘all substances are poisonous, there is none which is not and it is the dosage that differentiates poison and remedy’. Even water can be potentially fatal if too much is drunk (hyperhydration). So eat or drink anything in moderation!
