Fruit pomace extracts influence the activity of endothelial nitric oxide synthase

Abstract

The consumption of fruits and fruit-derived products correlates with a reduced risk for cardiovascular diseases [1]. With a European production of 10.7 billion litres of fruit juice in 2011, fruit-juice industry generates tons of fruit waste every year [2]. As fruit pressing is an incomplete extraction process, pomaces represent a valuable source of fruit-derived bioactive compounds [3]. Nitric oxide (NO) produced by the endothelial nitric oxide synthase (eNOS) is a protective factor counteracting inflammatory processes and platelet activation. In addition, NO promotes vasorelaxation. Therefore, pomace extracts obtained from Austrian fruits (apple, apricot, elderberry and bilberry) were investigated for their potential to activate eNOS. Extracts of dried fruit pomace were produced by Accelerated Solvent Extraction (ASE) using methanol/water (70/30) (MW), ethylacetate (EtOAc), dichloromethane (DCM) and hexane (Hex). eNOS activity was evaluated by the 14C-L-arginine to 14C-L-citrulline conversion assay (ACCA) [4] in endothelium-derived EA.hy926 cells. Apple and apricot pomace extracts (EtOAc, DCM) as well as elderberry pomace extracts (MW, DCM, Hex) caused a significant increase in eNOS activity at the concentration of 50 µg/mL, while neither of the bilberry extracts showed significant effects at this concentration. In particular, the MW elderberry extract showed the highest eNOS activation (1.5-fold compared to negative control). In conclusion, apple, apricot and elderberry pomaces obtained from the Austrian fruit juice industry represent an easy-accessible raw material for the isolation of eNOS activating compounds.