Abstract 913: Determination of individual isothiocyanates/indoles occurring as a result of glucosinolate degradation and their relation to biological potential of different Brassica plants

Abstract

Abstract Glucosinolates (GLs), and particularly two classes of their degradation products - isothiocyanates (ITC) and indoles - released upon myrosinase catalyzed hydrolysis, belong to the most promising chemopreventive dietary components. Despite their wide use in research on chemopreventive mechanisms and industrial utilization in the production of e.g. dietary supplements, the methods of reliable characterization of myrosinase-GLs system have been underdeveloped. The biological potential ascribed to ITC and indoles, in the case of actual Brassica plant samples, is still assessed based on GL content, though it is well known that these two types of derivatives are not the only ones that are formed following myrosinase action. This means that the relationship between content and composition of bioactive Brassica ingredients and biological effect can not be properly assessed or predicted. The aim of our research was to optimize known or to develop novel methods that will ensure precise description of GLs-myrosinase system in any source, natural or processed, and to relate the rate of formation of ITC/indoles to biological effects observed. The methods optimized include: determinations of GLs by HPLC-ESI-MS [1], myrosinase activity by pH-static method [2], indoles by HPLC with fluorescent detection [3], as well as novel derivatization of ITC enabling their identification and quantitation by HPLC-DAD-MS. The developed methods were applied to characterize an array of Brassica samples and the results of chemical analyses were compared with determined cytotoxicity (MTT test), genotoxicity (comet assay) and capability of covalent DNA modification (restriction analysis [5]). GL conversion rate to ITC and indoles was found to differ significantly not only between Brassica species but also between individual plant parts and was independent of myrosinase activity. The yield of conversion of individual GLs to ITC was also not identical. The biological activity in tests used turned out to be mostly related to indoles, some of which were particularly toxic. The developed set of methods should ensure better and safer exploitation of chemopreventive potential of Brassica plants. 1. Kusznierewicz et al., J. Chromatography A, 1278: 108, 2013 2. Piekarska et al., Ind. Crops Prod., 50: 58, 2013 3. Pilipczuk et al., Food Anal. Meth., submitted 4. Pilipczuk et al., Quantitative and qualitative determination of isothiocyanates in plant extracts by HPLC after chemical derivatisation, manuscript in the final stage of preparation 5. Kolodziejski et al., Food Chem. Toxicol., 75: 118, 2015 Citation Format: Agnieszka Bartoszek, Barbara Kusznierewicz, Anna Piekarska, Dominik Kołodziejski, Tadeusz Pilipczuk, Izabela Koss-Mikołajczyk, Jacek Namieśnik. Determination of individual isothiocyanates/indoles occurring as a result of glucosinolate degradation and their relation to biological potential of different Brassica plants. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 913. doi:10.1158/1538-7445.AM2015-913