Biotransformation of bioactive compounds from lentils: an approach based on antioxidant activities of extracts obtained after germination and fermentation

Lentils has been studied in relation to their effects on the reduction of the development of chronic diseases or decrease of the symptoms associated to these, such as cardiovascular and neurodegenerative diseases and cancers. Besides, lentils are an excellent source of nutrients and bioactive substances, being a grain rich in protein, fiber, vitamins, minerals and phenolic compounds with antioxidant properties. Processes such as fermentation and germination can be used as efficient strategies for production of multifunctional ingredients by improving biological properties. Germination causes important changes in biochemical and nutritional characteristics of lentils, while fermentation increases the content and the bioavailability and bioaccessibility of bioactive compounds. Thus, the aim of the present study was to investigate the antioxidant properties of extracts obtained from lentils after fermentation and germination. In order to determine the most adequate way to recovery the bioactive compounds, the extraction process using different solvents was studied. For germination, lentil grains were soaked in distilled water followed by distribution in a tray with filter paper. The material was kept at room temperature in the dark and watered daily for 96 h. Fermentation was carried out using lentils flour as substrate with an initial moisture adjusted to 50% and Aspergillus oryzae as inoculum. Control samples were prepared and incubated at the same fermentation conditions without the microorganism. The extracts containing the antioxidant compounds were obtained from non-germinated, germinated, non-fermented and fermented lentils using distilled water and acidified (0.1% HCl) methanol solution (70%) as solvents. The antioxidant properties were measured by DPPH, FRAP and ABTS assays, and total phenolic compounds (TPC) were determined by Folin-Ciocalteu method. The relative antioxidant activity and TPC were calculated considering the values for the modified lentils (germinated or fermented) in relation to the control samples. In general, the results showed that the antioxidant activities of the extracts obtained from germinated lentils with acidified methanol were significantly higher than those obtained with distilled water. The following results were the highest values detected for the aqueous/methanolic extracts, respectively, from fermented lentils: a) TPC: 1.45 / 1.38 mg of gallic acid equivalent per gram of sample (mg GAE/g), b) FRAP assay: 5.02 / 10.31 μmol of Trolox equivalents per g of sample (μmol TE/g), c) DPPH-radical scavenging: 1.76 / 3.43 μmol TE/g and c) ABTS assay: 2.93 / 5.90 μmol TE/g. The
aqueous/methanolic extracts, respectively, obtained from germinated lentils showed the following results: a) TPC: 5.06 / 4.94 mg GAE/g, b) FRAP assay: 12.74 / 26.72 μmol TE/g, c) DPPH-radical scavenging: 55.86 / 72.59 μmol TE/g and c) ABTS assay: 48.57 / 53.30 μmol TE/g. The most highlighted and positive results were observed under the conditions described below: a) lentils fermentation at 24 and 48h allowed obtaining aqueous extracts with increases of 40 and 18% in the antioxidant activities measured by DPPH and FRAP methods, respectively, compared to the non-fermented samples and b) for methanolic extracts, increases in antioxidant activities ranging from 12 to 19%, measured by DPPH, FRAP and ABTS assays were detected after 24h fermentation.

Financial support: This study was financed in part by the Fundo de Apoio ao Ensino, à Pesquisa e Extensão (FAEPEX) - Unicamp.