Composition analysis and antioxidant activity of purified Boletus auripes pigment using macroporous resin

Abstract

Fungi pigment has been widely used in the food industry due to their high safety and various physiological activities, however, study on the Boletus auripes pigment (BAP) has rarely been reported. The aim of the present study was to optimize the purification process of BAP using macroporous resin. Moreover, the chemical composition and antioxidant activity of the purified BAP (PBAP) were also evaluated. The optimal purification parameters for the resin of XDA-7 were as follows: at pH 6.0, the concentration of BAP was 2.0 mg/ml (30 ml) with a loading flow rate of 2.0 ml/min, and 80% ethanol was used as the eluent solvent with the elution flow rate of 1.5 ml/min. The results showed that the purity of PBAP after purification by XDA-7 was 5.8 times higher than that of BAP. Fourier transform-infrared spectrometry showed that the absorption peaks of PBAP were associated with the signals of the aldoketones functional group. Ultra performance liquid chromatographytandem-mass spectrometry indicated that there were 32 components were identified from the PBAP, including 15 organic acids, 9 glycosides, 3 esters, 3 vitamins, and 2 alkaloids. The scavenging capacity of DPPH free radical (DPPH·), ABTS free radical (ABTS+.), Hydroxyl free radical (·OH), and the reducing power was measured to investigate the antioxidant capacity of BAP and PBAP. The obtained results showed that the two pigments possessed good antioxidant capacity with the dose–effect relationship. The IC50 values of PBAP for scavenging DPPH·, ABTS+., and ·OH were 0.048, 0.001, and 0.31 mg/ml, respectively, and they were much higher than the corresponding results that showed 0.103, 0.049, and 1.295 mg/ml of the BAP. Obviously, the antioxidant activity of BAP was significantly enhanced after purification. In short, the study provided a reference for the further development and utilization of the pigment from B. auripes. Novelty impact statement As a new source of natural pigments, Boletus auripes pigment (BAP) has not attracted the attention of researchers. In this article, BAP was purified by macroporous resin, and its physicochemical property and antioxidant activity were analyzed. The relevant research could establish the biological foundation for building a quantitative structure–function relationship and the application of purified BAP in functional food and medicine.