Antioxidant dietary fibres from guavira fruit pomace

Campomanesia sp, popularly known as guavira, is a native fruit from the Brazilian Cerrado with established biological effects on its pulp, such as antimicrobial, anti-inflammatory, antinociceptive and antioxidant activity. Moreover, exotic fruits and their byproducts may be valuable sources of dietary fibres (DF), equivalent to pectins, useful for food industry and human health. The aim of this study was to determine antioxidant properties of DF containing fraction (CPW), present in pomace flour obtained as agroindustrial waste of a guavira pulp industry. Pectins from guavira fruit pomace were obtained by aqueous extraction, analysed by sugar composition, GPC and NMR spectroscopy analyses. Also, in vitro trolox equivalent antioxidant capacity (TEAC) of the extract was evaluated, as well as its quantitative phenolic and protein composition. MTT and DCFH-DA assay were performed to assess, respectively, changes in cell viability and the potential intracellular antioxidant activity against H2O2-induced oxidative stress in murine fibroblast cell line (NIH 3T3). A fraction containing a mixture of arabinan-rich pectic polysaccharides, highly-methoxylated homogalacturonan (DM = 90%) and small amounts of arabinogalactan was obtained from the aqueous extraction. It also presented 1.8% of protein and total phenolic content of 3.2 g GAE/100 g of CPW sample, indicating that phenolic compounds may be complexed with the dietary fibres. The inhibitory effect of CPW on ABTS radicals was 67.4% at 1.0 mg/mL, indicating that it has potential on free radical scavenging and could help preventing oxidative stress. Also, the incubation of NIH 3T3 cells with this extract during 48h remarkably decreased the levels of Reactive Oxygen Species (ROS) as well as the H2O2-induced cytotoxic effect. The results indicate that polysaccharides from guavira fruit pomace were able to exert intracellular antioxidant activity in murine fibroblasts, inducing a protection against pro-oxidant conditions.