The role of plant processing for the cancer preventive potential of Ethiopian kale (Brassica carinata)

Grace Akinyi Odongo; Nina Schlotz; Corinna Herz; Franziska S Hanschen; Susanne Baldermann; Susanne Neugart; Bernhard Trierweiler; Lara Frommherz; Charles M A P Franz; Benard Ngwene; Abraham Wahid Luvonga; Monika Schreiner; Sascha Rohn; Evelyn Lamy

doi:10.1080/16546628.2017.1271527

The role of plant processing for the cancer preventive potential of Ethiopian kale (Brassica carinata)

Food Nutr Res. 2017 Jan 31;61(1):1271527. doi: 10.1080/16546628.2017.1271527. eCollection 2017.

Affiliations

¹ Molecular Preventive Medicine, Institute for Prevention and Cancer Epidemiology, University of Freiburg - Medical Center , Freiburg im Breisgau , Germany.
² Department of Plant Quality, Leibniz Institute of Vegetable and Ornamental Crops Grossbeeren/Erfurt e. V ., Großbeeren , Germany.
³ Department of Safety and Quality of Fruits and Vegetables , Max Rubner-Institut , Karlsruhe , Germany.
⁴ Department of Microbiology and Biotechnology, Max Rubner-Institut , Karlsruhe , Germany.
⁵ Hamburg School of Food Science, Institute of Food Chemistry, University of Hamburg , Hamburg , Germany.

Abstract

Background: Ethiopian kale (Brassica carinata) is a horticulturally important crop used as leafy vegetable in large parts of East and Southern Africa. The leaves are reported to contain high concentrations of health-promoting secondary plant metabolites. However, scientific knowledge on their health benefits is scarce. Objective: This study aimed to determine the cancer preventive potential of B. carinata using a human liver in vitro model focusing on processing effects on the pattern of secondary plant metabolites and bioactivity. Design: B. carinata was cultivated under controlled conditions and differentially processed (raw, fermented, or cooked) after harvesting. Human liver cancer cells (HepG2) were treated with ethanolic extracts of raw or processed B. carinata leaves and analyzed for their anti-genotoxic, anti-oxidant, and cytostatic potential. Chemical analyses were carried out on glucosinolates including breakdown products, phenolic compounds, carotenoids, and chlorophyll content. Results: Pre-treatment with B. carinata extracts concentration dependently reduced aflatoxin-induced DNA damage in the Comet assay, reduced the production of reactive oxygen species as determined by electron paramagnetic resonance spectroscopy, and induced Nrf2-mediated gene expression. Increasing extract concentrations also promoted cytostasis. Processing had a significant effect on the content of secondary plant metabolites. However, different processing methodologies did not dramatically decrease bioactivity, but enhanced the protective effect in some of the endpoints studied. Conclusion: Our findings highlight the cancer preventive potential of B. carinata as indicated by the protection of human liver cells against aflatoxin in vitro. In general, consumption of B. carinata should be encouraged as part of chemopreventive measures to combat prevalence of aflatoxin-induced diseases.

Keywords: Aflatoxin B1; African leafy vegetables; Brassicaceae; anti-genotoxicity; cancer chemoprevention; glucosinolates; polyphenols; secondary plant metabolites.

Grants and funding

This work was conducted within the African-German Project ‘Horticultural Innovation and Learning for Improved Nutrition and Livelihood in East Africa (HORTINLEA)’ funded by the German Federal Ministry of Education and Research (BMBF) in the context of the funding measure ‘GlobE – Global Food Security’ as part of the ‘National Research Strategy BioEconomy 2030’ framework program (project number 031A248H, 031A248I, 031A248J 031A248K). The article processing charge was funded by the German Research Foundation (DFG) and the University of Freiburg in the funding program Open Access Publishing.