Evaluation of prebiotic activity of polysaccharides extracted from acorn

Background and objectives: It is well accepted that the modulation of the intestinal microbiota of the host could be helpful in the prevention of chronic diseases, including obesity and related disorders, such as type 2 diabetes. Prebiotics are non-digestible food ingredient that beneficially affects the host by selectively stimulate the growth and / or activity of probiotics in the large intestine and thus improves host health. Some health benefits include: better immune response, effect on mineral absorption, reduction in incidence of tumours and cancers, reduced risk of infection and diarrhea, reduction in incidence of diseases such as intestinal disease, cardiovascular disease, non-insulin dependent diabetes, obesity and osteoporosis. The aim of this study was to evaluate the prebiotic potential of polysaccharides isolated from acorn fruit (AP), antioxidant activity, relation between structural property and functional property.

Materials and methods: AP were extracted from acorn fruit after defatting, extraction by hot water and precipitation with ethanol. Then in vitro resistance of AP to acidic and enzymatic digestion was evaluated. In the second step the effect of AP on probiotic (L.plantarum A7) growth was studied in comparison to commercial prebiotic (Inulin-In) and glucose supplemented medium. The short chain fatty acids (SCFA) or the fermentation end products in AP and In supplemented media with probiotic (L.plantarum A7) were analysed using gas chromatography- mass spectrometry (GC/MS). The antioxidant activity of AP was evaluated by DPPH scavenging ability. FTIR spectroscopy and NMR were used to study structural properties and to identify its functional groups of AP.

Results: AP showed that it was resistant to hydrolysis by artificial human gastric juice, giving maximum hydrolysis of 3%. AP also found capable of the growth stimulating and viability increasing of studied probiotic (L.plantarum A7). The short chain fatty acids profile in AP and In supplemented media was dominated by acetic acid, followed by minor amounts of propionic acid and butyric acid were detected in AP and In supplemented media, respectively. AP scavenged DPPH radicals by 69.94± 1.35 %, 82.24± 1.78 at 20 mg/ml, 40mg/ml. Characteristic bands related to antioxidant capability including carboxyl, sulphate and β-glycosidic linkages were observed in IR and NMR spectra of AP.
Conclusion: Study conducted reflects a good sign for the AP to be exploited as a promising prebiotic Our results showed high antioxidant activity of AP seems to be related to better prebiotic potential. Because of increasing demand for prebiotics and high price of commercially available prebiotics, acorn could be a potential source of prebiotic compounds which may be used in functional food and healthier products.