Superior heavy metal binding, antioxidant amd chemopreventive action of black sesame pigment after simulated gastrointestinal digestion: toward the development of a food supplement

E-mail: panzella@unina.it We recently developed an improved purification procedure to obtain black sesame pigment (BSP), involving fat removal followed by an optimized hydrolytic protocol. BSP thus obtained displayed good antioxidant efficiency in several chemical assays.1,2 In order to assess the potential of BSP as food supplement, we have now explored the structural transformations of this pigment in model systems of stomach and gut digestion. The release of low molecular weight compounds from BSP was evaluated by a simulated digestion procedure involving an initial treatment with pepsin at pH 1.7 followed by treatment with a mixture of porcine bile salts and pancreatin at pH 7.5. HPLC analysis indicated that BSP is transformed under the slight alkaline pH conditions mimicking the intestinal environment and favoring swelling of the pigment and hydrolytic reactions. All of the low molecular weight components released have a potential to pass into the serum as evidenced by a serum availability model. The most abundant of these components was identified as vanillic acid. Both the insoluble pigment fraction (fraction A) and the low molecular weight components (fraction B) exhibited efficient antioxidant properties in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. Both fractions proved to be non-toxic and exhibited marked protective effects against reactive oxygen species (ROS) generation and cell damage evaluated as lactate dehydrogenase (LDH) leakage (Fig. 1) induced by 400 M tert-butylhydroperoxide (t-BOOH) in human hepatocarcinoma HepG2 cell line. In other experiments the chelating properties of the digested pigment were evaluated toward heavy metals such as lead, mercury and cadmium, which occur in food (e.g. 0.05 g/g, 0.09 g/g and 0.035 g/g, respectively in fish and shellfish)3 and are highly toxic due to their non-biodegradable nature and prolonged biological half-life. At a metal concentration in the range 1.5-3 g/g with a pigment dose of 0.05 mg/mL a removal higher than 80% was obtained with lead and mercury, but less than 40% in the case of cadmium (Fig.2). The metal binding properties together with the chemopreventive activity open new perspectives toward the use of BSP as a food supplement for the prevention of neurodegenerative and oxidative stress based diseases. 1. Eidenberger, T. PCT Int. Appl. WO 2010012751, 2010 2. Panzella, L.; Eidenberger, T.; Napolitano, A.; d’Ischia, M. J. Agric. Food Chem. 2012, 60,8895-8901. 3. Llobet, J. M.; Falcoä, G.; Casas, C.; Teixidoä, A.; Domingo, J. L. J. Agric. Food Chem. 2003, 51, 838-842.