Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2003
Publication Date: May 14, 2003
Citation: Harrison Jr, H.F., Peterson, J.K., Snook, M.E., Bohac, J., Jackson, D.M. 2003. Quantitation and potential biological activity of caffeci acid in sweetpotato [Ipomoea batatas (L.) Lam.] storage roots. Journal of Agricultural and Food Chemistry. 51(10):2943-2948. Interpretive Summary: The outer skin (periderm) of sweetpotato is a barrier that protects roots from attack by diseases. Components of the periderm also inhibit the growth of weeds, insects and pathogenic fungi and contribute to the defense against diseases and predators. In this paper we report that the periderms of different sweetpotato varieties vary greatly in periderm content of caffeic acid. Caffeic acid is a simple phenolic acid that occurs in all plants. However, the caffeic acid level in the periderm of some sweetpotatoes was much higher than levels normally found in plants. Caffeic acid was not high in the inner part of sweetpotatoes that had high periderm contents. Caffeic acid inhibited the growth of four fungi that are sweetpotato pathogens and the germination of proso millet which indicates that caffeic acid contributes to the defense of sweetpotato roots against natural enemies such as diseases and weeds in varieties that have high levels. This finding is important because it may allow sweetpotato breeder to develop pest resistant varieties by selecting for lines with high levels of caffeic acid. Selecting sweetpotatoes for caffeic acid content may facilitate breeding for pest resistance. Simple and rapid laboratory procedures are used to determine caffeic acid content, but selecting for pest resistance often takes several years of laborious field evaluation. Also, caffeic acid is considered to provide human health benefits, because it functions as an antioxidant and protects against viruses. Sweetpotato varieties with higher caffeic acid contents may be more nutritious than those with low contents.
Technical Abstract: The caffeic acid content of storage root periderm and cortex tissues of genetically diverse sweetpotato cultivars and breeding clones was analyzed by high performance liquid chromatography. Periderm caffeic acid content of the clones ranged from 7.97 to 0.008 mg/mg dry weight, while the highest cortex content was 0.047 mg/ml. Clones varied greatly in periderm caffeic acid content in all four field experiments, but there were also difference between experiments in caffeic acid content averaged for all clones. These findings indicate that periderm caffeic acid content is subject to genetic and environmental influences. Caffeic acid inhibited the growth of four sweetpotato pathogenic fungi and germination of proso millet seeds in petri dish bioassays. These findings suggest that high periderm caffeic acid levels contribute to the storage root defense chemistry in some sweetpotato genotypes.