Hairy Root Cultures as a Source of Phenolic Antioxidants: Simple Phenolics, Phenolic Acids, Phenylethanoids, and Hydroxycinnamates

Plant-derived antioxidants are intrinsic components of human diet and factors implicated in tolerance mechanisms against environmental stresses in both plants and humans. They are being used as food preservatives and additives or ingredients of cosmetics. For nearly forty years, Rhizobium rhizogenes-transformed roots (hairy roots) have been studied in respect to their usability as producers of plant specialized metabolites of different, primarily medical applications. Moreover, the hairy root cultures have proven their value as a tool in crop plant improvement and in plant secondary metabolism investigations. Though cultivated plants remain a major source of plant polyphenolics of economic importance, the decline in biodiversity caused by climate changes and overexploitation of natural resources may increase the interest in hairy roots as a productive and renewable source of biologically active compounds. The present review examines hairy roots as efficient producers of simple phenolics, phenylethanoids, and hydroxycinnamates of plant origin and summarizes efforts to maximize the product yield. Attempts to use Rhizobium rhizogenes-mediated genetic transformation for inducing enhanced production of the plant phenolics/polyphenolics in crop plants are also mentioned.

Automated summary

Plant-derived antioxidants are important for human health and stress tolerance in both plants and humans. Hairy roots, transformed by Rhizobium rhizogenes, have been studied as potential sources of plant metabolites with medical applications for almost forty years. They have also shown value in crop improvement and secondary metabolism research. Hairy roots may become more important as a sustainable source of biologically active compounds due to biodiversity decline caused by climate change and overexploitation of natural resources. This review focuses on the efficient production of phenolic compounds in hairy roots and efforts to increase yield, including genetic transformation of crop plants.