Moringa: the science behind the miracle tree
Submitted by rau on 03 March 2011
Reports in the press about the miraculous nature of the tree may be exaggerated, but it does have some truly impressive properties. Native to northern India but now found widely in Asia, Africa and Latin America, moringas have been used in villages in developing countries for hundreds of years, their uses ranging from traditional medicine, food and cooking oil, to natural pesticide, domestic cleaning agent, and – the latest addition – biofuel.
Moringa oleifera can help with the first purification step – not only in the developing world but also in the developed world. In industrial water treatment plants, the most prevalent coagulating agents used today are aluminium salts. Most particles that need to be removed from water are charged, so coagulating agents are usually ions; because the coagulating efficiency increases with the square of the coagulating agent’s ionic charge, polyvalent ions such as aluminium are very efficient. However, there is concern – albeit controversial – that long-term exposure to aluminium may be associated with the development of neurodegenerative diseases. Iron salts are an alternative, but they are more difficult to use, as their solubility changes with pH.
In certain rural areas of Sudan, women already use M. oleifera to purify water: when collecting water from the River Nile, they place the powdered seeds in a small cloth bag with a thread attached. This is then swirled around in the bucket of turbid water, until the fine particles and bacteria clump together with M. oleifera powder, sinking and settling to the bottom. For drinking water though, the water needs to be purified further – by boiling, filtering through sand or placing it in direct sunlight in a clear bottle for a couple of hours (solarising; see Folkard et al., 1999). You can try a similar technique yourself in class (see box).
The mother of moringa researcher Dr Kwaambwa demonstrates how the seeds are treated for water purification
Images courtesy of Dr Majority Kwaambwa, University of Botswana
Although a successful pilot study was performed at Thyolo water treatment works in Malawi in 1989-1994 (see Folkard & Sutherland, 2002), developing future industrial treatment methods from M. oleifera relies on knowing exactly what processes take place during the purification. Researchers already know that the active ingredient in the seeds is protein, which accounts for 30-40% of the seeds’ weight. There are at least two proteins that may be active: they are water-soluble and quite small, about 6-16 kDa, so they can readily diffuse out of the cloth bags. At higher concentrations, they aggregate even in solution due to their substantial hydrophobic regions. The protein adsorbs onto contaminant particles, which then clump together and can be separated and extracted.
The team used a neutron beam at the Institut Laue Langevinw2 in Grenoble, France, in a technique called neutron reflectometry, to measure the thickness, density and coarseness of the forming protein layer.
How does this technique work? When you see a layer of petrol on a puddle, you can see a variety of iridescent colours: light bounces off both the top and bottom of the petrol layer. The reflected light waves will be slightly out of phase, and depending on the thickness of the petrol layer, will either add up or cancel each other out, resulting in different colours. Many more materials are transparent to neutrons than to light, and neutron wavelengths are also about one thousand times shorter (0.2-2 nm) than those of light (about 0.5 µm), which is why a neutron beam can be used to measure layers of protein a single molecule thick.
Mathur welcomes the scientific scrutiny. “We feel that the moringa tree is very important and needs to be brought to the attention of scientists who can do further research,” he says. “It is not widely known in the Western world yet because it doesn’t grow there.” In the future, the miracle tree could live up to its name. “The moringa could save millions of lives around the world for years to come,” states Mathur. “I cannot emphasise enough how important it is.”
Seeds of the Moringa oleifera tree are cheaply available online, as the tree is grown for decorative purposes.
Water will require different amounts of M. oleifera powder to purify it, depending on the impurities present. Around 50-150 mg of ground seeds treat one litre of water: as a rule of thumb, powder from one seed will be sufficient for one litre of very turbid or two litres of slightly turbid water. Experimenting with small amounts of water in a jar will help you work out the correct amount of powder and the optimal stirring times.
You may want to compare the water quality achieved with M. oleifera seeds to that achieved with other methods (see Mitchell et al., 2008, for an example of a different water purification method), and run a competition for the most efficient method of water purification.
Both the seeds and the seed powder can be stored, but the paste (made in step 4) should be freshly made every time water is to be purified.
For safety reasons, water purified in class must not be used as drinking water.
Folkard G, Sutherland J, Shaw R (1999) Water clarification using Moringa oleifera seed coagulant. In Shaw, RJ (ed) Running Water: More Technical Briefs on Health, Water and Sanitation pp 109-112. Rugby, UK: IT Publications. ISBN: 9781853394508
Ghebremichael KA et al. (2005) A simple purification and activity assay of the coagulant protein from Moringa oleifera seed. Water Research 39: 2338-2344. doi: 10.1016/j.watres.2005.04.012
Kwaambwa HM, Hellsing M, Rennie AR (2010) Adsorption of a water treatment protein from Moringa oleifera seeds to a silicon oxide surface studied by neutron reflection. Langmuir 26(6): 3902-3910. doi: 10.1021/la9031046
Mitchell WA et al. (2008) Science for the Next Generation: activities for primary school. Science in School 10: 64-69. www.scienceinschool.org/2008/issue10/nextgeneration
w1 – Trees for Life International provides an international forum on beneficial trees and plants, and has been promoting the moringa tree for many years, sending literature and information to universities, embassies and heads of state, as well as producing educational material for schools. See: www.treesforlife.org
w2 – To learn more about the Institut Laue-Langevin, see: www.ill.eu
If you enjoyed reading this article, take a look at other Science in School articles about research done at ILL. See: www.scienceinschool.org/ill
Sue Nelson is an award-winning UK science broadcaster and writer. A physics graduate, Sue also studied space science and astronomy at the University of Michigan as a Knight Wallace journalism fellow in 2002 and recently completed a one-year Nesta Dream Time fellowship writing science-based dramas. Her reports have appeared on all the BBC’s national TV and radio news bulletins. Co-author of the popular science book How to Clone the Perfect Blonde, Sue has written for The Sunday Times, The Observer, The Guardian and The Independent and has contributed opinion columns on science for the Times.
Dr Marlene Rau was born in Germany and grew up in Spain. After obtaining a PhD in developmental biology at the European Molecular Biology Laboratory in Heidelberg, Germany, she studied journalism and went into science communication. Since 2008, she has been one of the editors of Science in School.
This is a thought-provoking article that uses theoretical science (binding abilities of ions, neutron reflection techniques) to explain a real-life situation (using seeds to purify water).
Ideas from this article could be used with students of all ages to carry out some innovative practical work, with appropriate risk assessments. M. oleifera seeds can be bought via the Internet, if you are not lucky enough to have them grow locally, and their effects on clarifying water can be compared to those of other seeds. Are M. oleifera seeds really much better? Younger students could have a lot of fun grinding up different seeds and coming up with different ways of measuring how clear their dirty water becomes.
Older students could take this further and carry out investigations linked to using different parts of the seeds and relating this to seed biochemistry, or compare seeds treated in different ways, e.g. dried versus fresh. Researching the scientific basis of the seed-driven clarification process would certainly be challenging for the most able students.
The article fits well into a number of curricular topics: biology of seeds / biochemistry of extracts; chemistry of water purification / physical behaviour of the salts; physics – perhaps something to do with investigating density of layers – and looking at alternative methods. The idea could form the basis of a cross-curricular project with social science lessons, because of the good links with sustainability and renewable resources.
The article is suitable as a comprehension exercise for students aged 16 and older. Possible questions to ask in a biology lesson include:
The article can also form the basis of discussion. Possible topics include:
Sue Howarth, UK