Plants as biofactories: Stress-induced production of chlorogenic acid isomers in potato tubers as affected by wounding intensity and storage time
Introduction
Potato (Solanum tuberosum L.) is one of the most important crops around the world. In the year 2012, ∼324 million tons were produced worldwide (FAOSTAT, 2012). However, in the US supply chain ∼6% of potato production is lost due to poor postharvest practices (USDA, 2012). Alternative uses for potatoes considered as waste should be of interest for the potato industry. In the past few years, the use of stressed-plants as biofactories of phenolic compounds (PC) has been proposed as an alternative use for horticultural crops (Jacobo-Velázquez and Cisneros-Zevallos, 2012).
When potato tubers are subjected to wounding stress, chlorogenic acids (CGAs) are produced and converted into lignin and suberin during the wound-healing process (Gamborg, 1967, Dean and Kolattukudy, 1977, Friedman, 1997, Lulai and Corsini, 1998, Bernards et al., 2000, Bernards and Razem, 2001, Mattila and Hellström, 2007). The CGAs are PC with potential applications for the treatment and prevention of Alzheimer (Kim et al., 2005), obesity (Thom, 2007), hepatitis B (Wang et al., 2009), and cancer (Yagasaki et al., 2000, Aggarwal and Shishodia, 2006, Kurata et al., 2007, Noratto et al., 2009, Weng and Yen, 2012). Therefore, the application of wounding-stress in potato could be used as an emerging technology to induce the production of CGAs. The stressed-tissue can be subjected to downstream processing to recover and purify CGAs with potential applications in the pharmaceutical and dietary supplements industries.
However, depending on the wounding intensity applied in plant tissues, the biosynthesis and conversion rates of CGAs will change during storage time, and thus it is important to optimize the abiotic stress conditions that lead with the highest accumulation of CGAs. Therefore, the present project objective was to evaluate the effect of wounding intensity and storage time (144 h at 10 °C) on the accumulation of total and individual PC in potato tubers.
Section snippets
Chemicals
Ferulic acid (FA), p-coumaric acid (p-CA), chlorogenic acid (CGA), methanol (HPLC grade), water (HPLC grade), orthophosphoric acid and formic acid were purchased from Sigma Chemical Co. (St. Louis, MO, USA).
Plant material, processing and storage study
White potatoes (S. tuberosum L.) were obtained from a local market (HEB, Monterrey, N.L. Mexico), sorted, washed and disinfected with chlorinated water (200 ppm, pH 6.5). Three different wounding intensities were prepared (slices, pie-cuts and shreds) as shown in Fig. 1. Whole potatoes were
Effect of wounding stress and storage time on the accumulation of total phenolic compounds (PC) of potato tissue
The total PC content of samples was determined before and during 144 h of storage (Fig. 2). The application of wounding stress to obtain slices and pie-cuts produced a significant increase (p < 0.05) on the total PC content of potato tubers during storage at 10 °C. However, when potato tubers were treated with the highest wounding intensity (shredded-potatoes), samples showed a significant decrease (p < 0.05) on the concentration of total PC. Likewise, no significant change (p > 0.05) on the total PC
Discussion
It is well known that wounding stress induces the phenylpropanoid metabolism in plants (Dixon and Paiva, 1995). In the particular case of potatoes, PC biosynthesized during the wound-healing process are utilized for the biosynthesis of suberin and lignin (Gamborg, 1967, Lulai and Corsini, 1998, Bernards et al., 2000, Bernards and Razem, 2001). Both polymers are produced as a defense mechanism to prevent water loss in wounded-plant tissues (Lulai and Corsini, 1998, Bernards and Razem, 2001,
Conclusion
The present study demonstrated the potential use of wounded-potato tubers as biofactories for the production of chlorogenic acid isomers. Furthermore, results demonstrated that the profile of PC accumulated in the wounded-tissue could be easily manipulated by wounding intensity and storage time to trigger the production of specific chlorogenic acid isomers. The wounded-potato with increased concentrations of chlorogenic acids could be used as a starting material for the extraction of high value
Acknowledgments
This study is based upon research supported by research funds from the Tecnológico de Monterrey – Research Chair Initiative (CAT 161) and Cátedra de Nutrigenómica – FEMSA, and Consejo Nacional de Ciencia y Tecnología (CONACYT, México) Grant (177012). Author A.M.T.-C. also acknowledge the scholarship (279532) from the Consejo Nacional de Ciencia y Tecnología (CONACYT, México).
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