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The sweet seeds of the Cerrado (Wooded Savanna)

In the carbohydrates stored by the vegetables could be the key to the conservation of the ecosystem

SILVESTRE SILVAFalse-barbatimão: huge potential for the production of an industrial gum currently importedSILVESTRE SILVA

Researchers have proven that the rational exploration of determined species can make possible the sustained development of the remaining woodland stands of the São Paulo Cerrado, in such a way that the owners of the land, although preserving the 20% of the area demanded by law, can still make a profit with this untouched part. The argument for the preservation of this environment came about within the thematic project that studied the mechanisms of the natural reserves of carbohydrates, coordinated by the biologist Marcos Silveira Buckeridge, of the Botanic Institute of the Department of the Environment.

At the meeting of researchers of the Biota-FAPESP program, carried out in December in the Intervales State Park, in the Ribeira Valley, Buckeridge demonstrated the results of his biochemical and physiological studies, which covered 62 native species of the Cerrado (Wooded Savanna) and the Atlantic Rain Forest, as well as six exotic species. He demonstrated various applications of carbohydrates abundant in the vegetables of these environments, from a food thickener and a substitute for an imported product used in kidney examinations, to a compound that gives greater mechanical resistance to paper.

Brazilian gum
Among the shrub trees whose importance grew during the project was the false-barbatimão [Rutin] (Dimorphandra mollis ), one of the legumes of greatest occurrence in the Cerrado of São Paulo and of the Central-West, and still found in the North East Caatinga – the vegetation of the semi-raid – of the country. Also known as faveira (bean plant), farinha (flour) or canafístula, it grows to some 8 to 14 meters in height and from its bark and bean pods, rutin, a compound in the form of a tasteless yellowish-greenish powder, is extracted. Rutin is normally used in the curing of leather, but it is believed that in humans it may increase the strength of the blood capillary vessels and the absorption of vitamin C.

Buckeridge showed that the seeds of the false-barbatimão – currently discarded – are rich in polysaccharides (long chains of sugar molecules) chemically identical to guar gum. This gum is used industrially as a thickener in yogurts and ice creams, medical capsules, as a lubricant for drill heads in oil prospecting and even as the wrapping in sticks of dynamite. Almost all is imported – each kilogram costs from US$ 18 to US$ 28 -, and it is generally extracted from the seeds of exotic species (non-native to Brazil) such as the Cyamopsis tetragonolobus, a leguminous bush from India and Pakistan. Guar gum, whose properties have been known since the decade of the 30’s, also reduces the absorption of fats and facilitates the intestinal absorption of carbohydrates.

Of the species studied, the false-barbatimão (Cassia Leptophylla) is the one that contains the most amount of polysaccharides galactomannan, which correspond to close to half of the dry weight of the seed and could substitute guar gum. “The yield of galactomannan from the seeds of the Dimorphandra mollis is among the highest found in nature”, comments the researcher.

Working with two groups of seeds, one from the Caatinga of Parnaíba (near the town of Piauí) and the other from the São Paulo Cerrado (near the town of Mogi-Guaçu), the group studied the germination and developed a dry extraction method of the polysaccharide that accumulates in the cellular walls of the seed. Through milling and sieving, a powder with 83.2% of galactomannan was obtained, a degree of purity similar to the commercial products. Tests on rabbits indicate that we are dealing with a non-toxic compound that could effectively be used as a foodstuff. There are signs of interest for the use of these seeds coming from Europe and Japan.

The false-barbatimão adapts itself well to dry and poor soils or to degraded areas. What is missing is to check on the ideal conditions for field production and the quantity that can be withdrawn from the Cerrado without causing any environmental impact. For Buckeridge, the rational exploration of Brazilian gum could stimulate the preservation of the ecosystem, which commercially would create a favorable environmental differential.

Kidney function
Another plant from the Cerrado, the Vernonia herbacea Rusby, yields a polysaccharide of the group of the frutans that has an identical behavior to that of inulin. This industrialized substance serves to measure the so-called glomerule filtration, which reveals the state of the renal functioning of patients. Studies that researchers at the Botanic Institute carried out on mice in 1996, in collaboration with the University of São Paulo, had previously demonstrated that the Vernonia is a viable alternative to inulin for clinical and academic uses.

Buckeridge’s team is finishing up these studies. “We are carrying out field and laboratory experiments with the goal of understanding the role of specific nutrients in growth and in the development of the plant”, he says. “After gaining an understanding of these points, we will be able to think on how to maximize productivity.” As to the use of the plant, there are optimistic signs. “The productivity of Vernonia is high, comparable to the improved species of plants grown in Europe for the manufacturing of inulin”, explains the biologist Maria Angela Machado de Carvalho.

The researchers compared the development and the contents of the fruit in plants that grow under different levels of nitrogenous fertilization. The conclusion is that nitrogenation can benefit the accumulation of inulin: fertilized plants exhibit in 12 months content close to that of others of two years of age, grown under similar conditions. Already the xylem-glucanes, present in all vegetables, have a potential use in the paper industry, to increase the paper’s mechanical resistance: tests done at the Aracruz cellulose plant at Buckeridge’s request have shown an increase of 40% in resistance to tearing.

The xylemglucanes are carbohydrates highly concentrated in the seed. An example is the seed of the jatoba-do-cerrado (Hymenaea stigonocarpa), which in the jargon of the IT world will be zipped (compacted), so that the quantity of carbohydrate that it contains will be around 40% of its dry weight.

In the laboratory
If the exploration of a plant was to involve devastation, a production method in the laboratory to obtain the desired substances could be adopted. For example, the Viguiera discolor – a herbaceous plant of the family of composites such as the camomile and the daisy – is also an alternative in the production of inulin, but it develops slowly: the part above ground (stalk and leaves) grows between the spring and the end of the fall and afterwards goes into hibernation.

Consequently, a goal of the group is to get to a biosynthesis of the fruit, through the culture of vegetal tissues. For this to happen, as well as the moments of greater production of frutans, there will also have to be an observation of the distribution of the sugars in the plant. “The distribution of the reserves between the different parts of the subterranean organism is highly complex, but the accumulation occurs essentially in the tuberous roots”, comments Buckeridge.

Winter strategies
The storage of sugars in seeds or subterranean structures is a very successful adaptation strategy, which guarantees the survival of the plant in the dry winter of the Cerrado. The production is started under adverse or stressful environmental conditions, such as water shortage, in an indication that these substances can be linked to the cellular water cycle control. One of the experiments compared the soluble carbohydrates of a native and abundant grass in the Cerrado, the Echinolaena inflexa, and one of the invading species, the Melinis minutiflora.

It was concluded that these species adopted different strategies in order to survive and to occupy environments subject to water shortages. In both, the levels of sugars increased during the winter (dry period), but the native plant contained ten times more of a group of compounds, the alcohol sugars, which help the plant to survive with little water.

These are evidences of, more than results, the work indicating new pathways, in the manner in which the researchers understand the moments of greater or lesser production of the polysaccharides found in the leaves, stalk, seeds or roots. “The carbohydrate reserves of the Cerrado vegetal can be managed in a sustainable form, with applications in the pharmaceutical and food industries and in the technological area”, says Buckeridge, the coordinator of the thematic project due to be concluded in March of 2003. Since 1998, the work has resulted in the publication of 27 scientific papers and in 19 master’s and doctorate theses, presented or being completed.

Three groups of essential sugars

Buckeridge’s team studied three groups of carbohydrates, a wide class of compounds that include the polysaccharides and represent close to 90% of the structure of the vegetal cellular wall: fructans, galactomannans and xylem glucanes. The last two are cellular wall carbohydrates, which concentrate themselves in seeds, and, among other functions, control the speed of the absorption of water.

Fructans also participate in the absorption of water, but are especially relevant for the development of species with vegetative reproduction, such as those of the family of composites. In this type of reproduction, the plant eliminates its upper part during a period of hibernation, which in the Cerrado, corresponds to the period of drought. The underground part – in the very part where the fructans are concentrated – lives on and from it new shoots will grow.”Since fructans are not metabolized by the human organism, they can be used without risk by the food and pharmaceutical industries”, says Maria Ângela, who studied the metabolism of these polysaccharides in species native to the Cerrado.

One of the types of frutans, those of short sugar chain, with only a few molecules of linked fructose, has a sweet taste. Identified by the acronym FOS (fructo-oligo saccharides), they come into the composition of products for diabetes and for diets for losing weght,or they can be used as additives in foods. Another type of longer chain saccharide, with more linked fructose molecules, is not sweet: the molecules link together in such a way that not a single fructose molecule can get loose to guarantee a flavor. Its potential use is in the pharmaceutical industry.

According to Buckeridge, the galactomannan – previously used by the Egyptian in mummification – have potentially a much wider use, as it is being shown now with the prospect of substituting imported guar gum, since both have the exact same chemical structure. The understanding of the structures of the carbohydrate reserves also impinges on the adjustments in day to day diet. Currently, due to the intense consumption of industrialized products, foodstuffs have become short of fibrous material, made up mainly of carbohydrates, but left out because they contain few calories – though they are important for the good working of the gastrointestinal system and for the prevention of illnesses.

In the face of this, Buckeridge’s team has published articles considering the possibility of modifying the composition of highly consumed plant fibers or of introducing certain fibers into foodstuffs of popular use. He gave an example: “For example, why not a bean with more fiber? Its tissue already has the necessary genes, which would only need to be added or unblocked.”

The Project
Conservation and Sustainable Use of the Vegetal Biodiversity of the Cerrado (Wooded Savanna) and Atlantic Rain Forest: the Carbohydrates and their Role in the Establishing and Maintenance of Plants in their Natural Environment (nº 98/05124-8); Modality Thematic Project; Coordinator Marcos Silveira Buckeridge – Botanic Institute of the State Secretary of the Environment; Investment R$ 309,845 and US$ 378,726