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Zob potječe sa Starog kontinenta. Plod ove biljke koristi se u prehrani ljudi preko 4000 godina zbog bogatog nutritivnog sastava i pozitivnog djelovanja na probavni sustav. Zob sadrži visoki udio proteina koji su kvalitetom izjednačeni sa proteinima soje. Također sadrži šećere, ß-glukane. Ovi linearni polisaharidi građeni su od molekula D-glukoze povezanih ß-(13) i ß-(14) vezama. U plodu zobi nalaze se i biljna ulja sa visokim udjelom nezasićenih masnih kiselina, fenolne komponente, saponini, fitinska kiselina, vitamini i minerali. ß-glukan je najvažnije prehrambeno vlakno u zrnu zobi koje je gotovo u potpunosti topljivo u vodi, te ima svojstvo formiranja viskoznih otopina. Prolaskom kroz tanko crijevo ß-glukani ostaju nepromijenjeni jer ne postoje hidrolitički enzimi koji bi ih razgradili. U debelom crijevu dolazi do njihove fermentacije bakterijama crijevne mikroflore. ß-glukani veće molekulske mase topljiviji su u vodi i doprinose većoj viskoznosti sadržaja u tankom crijevu. Zbog toga se stvara postojan sloj koji poput fizičke barijere sprječava apsorpciju kolesterola i reapsorpciju žučnih kiselina. Posljedično dolazi do pojačanog izlučivanja kolesterola i metabolita žučnih kiselina fecesom, a zatim do pojačane sinteze žučnih kiselina u jetri. S obzirom da je kolesterol prekursor u sintezi žučnih kiselina, prilikom tog procesa smanjuje se koncentracija cirkulirajućeg LDL kolesterola u krvi. Produkti fermentacije ß-glukana u debelom crijevu, kratkolančane masne kiseline, octena i propionska, uzrokuju inhibiciju sinteze kolesterola u jetri.ß-glukani smanjuju apsorpciju glukoze iz crijeva zbog čega se smanjuje i lučenje inzulina. Kratkolančane masne kiseline, propionska i maslačna, povećavaju ekspresiju transportera GLUT-4 u mišićima putem receptora PPAR, smanjujući tako inzulinsku rezistenciju. S obzirom da inzulinska rezistencija značajno utječe na razvoj hipertenzije, ß-glukani mogu utjecati na krvni tlak modulacijom metabolizma inzulina. ß-glukani utječu na osjećaj sitosti jer povećavaju viskoznost obroka, uzrokuju odgođeno pražnjenje želuca, usporenu probavu i smanjenu apsorpciju nutrijenata. Kratkolančane masne kiseline usporavaju motilitet crijeva tako što potiču oslobađanje gastrointestinalnog serotonina. Time se produljuje prolazak hrane kroz crijeva i trajanje osjećaja sitosti. Osim toga, kratkolančane masne kiseline potiču izlučivanje različitih hormona iz crijeva koji imaju važnu ulogu u regulaciji osjećaja sitosti: PYY, GLP-1, CCK i grelin. ß-glukani su supstrat samo za dobre bakterije crijevne mikroflore, dok ne ulaze u direktnu interakciju sa Escherichiom colli i drugim potencijalno patogenim bakterijama. Stoga ih svrstavamo u kategoriju prebiotika.U odnosu na druge polisaharide koji djeluju kao imunostimulatori, ß-glukani su djelotvorniji i protiv infektivnih bolesti i protiv karcinoma. Dokazano je da mogu stimulirati i humoralnu i staničnu imunost.Lokalni pripravci na bazi zobi djeluju protuupalno, smanjuju suhoću kože, svrbež i ljuštenje. Zbog toga se mogu koristiti za liječenje atopijskog dermatitisa i drugih kožnih bolesti. Osim ploda, u medicinske svrhe koristi se i zelen zobi. Najnovijim istraživanjima je dokazano da ekstrakt zeleni zobi poboljšava kognitivne funkcije kod starijih ljudi.S obzirom na izvanredna nutritivna i ljekovita svojstva postoji veliki potencijal za upotrebu zobi u svakodnevnoj prehrani, kao i za specifične preparate na bazi zobi u okviru farmaceutske industrije. Oats originates from the Old Continent. The fruit of this plant is used in human nutrition for more than 4000 years because of its rich nutritional composition and the positive effects on the digestive system. Oats contains a high proportion of proteins that are of quality equal to soy protein. It also contains sugars, beta-glucans. These linear polysaccharides are built of D-glucose monomers linked by ß-(13) and ß-(14) glycosidic bonds. The fruit of oats also contains vegetable oils with a high proportion of unsaturated fatty acids, phenolic compounds, saponins, phytic acid, vitamins and minerals. ß-glucan is the most important food fiber in a grain of oats, which is almost completely soluble in water and has the property of forming viscous solutions. Passing through the small intestine ß-glucans remain unchanged because there are no hydrolytic enzymes that can dissolve them, while in the colon their fermentation occurs with bacteria of the intestinal microflora. ß-glucans with the higher molecular weight are soluble in water, and contribute to the higher viscosity of the contents in the small intestine. Because of that a resistant layer is created, and like a physical barrier it prevents cholesterol absorption and reabsorption of bile acids. Consequently, there is increased secretion of cholesterol and bile acid metabolites in the feces, and the increased synthesis of bile acids in the liver. Since cholesterol is a precursor in the synthesis of bile acids, with this process concentration of circulating LDL cholesterol levels reduces. Products of fermentation of ß-glucan in the colon, short chain fatty acids, acetic and propionic acid, cause the inhibition of cholesterol synthesis in the liver. ß-glucans reduce the absorption of glucose from the intestine which reduces the secretion of insulin. Short chain fatty acids, propionic and butyric acids enhance the expression of the transporter GLUT-4 in the muscles by PPAR receptors, thereby reducing insulin resistance. Since insulin resistance is a significant influence on the development of hypertension, ß-glucans can affect blood pressure by modulating insulin metabolism. ß-glucans affect the feeling of satiety by increasing the viscosity of a meal, causing delayed gastric emptying, slow digestion and reduced absorption of nutrients. Short chain fatty acids slow down intestinal motility by stimulating release of the gastrointestinal serotonin. This prolongs the passage of food through the intestines and the feeling of satiety. In addition, short chain fatty acids stimulate different gut hormones that play an important role in the regulation of feeling satiety: PYY, GLP-1, CCK, and ghrelin. ß-glucans are substrate only for beneficial bacteria of the intestinal microflora, while not being in direct interaction with Escherichia colli and other potentially pathogenic bacteria. Therefore, they are classified in the category of prebiotics. Compared to other polysaccharides which act as immunostimulators, ß-glucans are most effective against infectious diseases and cancer. It has been proven that ß-glucans can stimulate the humoral and cellular immunity. Local preparations based on oats have anti-inflammatory effect, reduce skin dryness, itching and peeling. They can therefore be used for the treatment of atopic dermatitis and other skin diseases. For medical purposes other than grain, the green oats is also used. Latest researches have proven that an extract of green oats improves cognitive function in elderly. Finally, this extraordinary plant shows emense potential for the everyday use in nutrition, as well as for the specific applications in the field of pharmaceutical industry. |
