ARS | Publication request: Polyphenol content and antioxidant capacity of eggplant pulp

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 22, 2008
Publication Date: June 1, 2009
Citation: Singh, A.P., Luthria, D., Wilson, T., Vorsa, N., Singh, V., Banuelos, G.S., Pasakdee, S. 2009. Polyphenol content and antioxidant capacity of eggplant pulp. Food Chemistry. 114(3):955-961.

Interpretive Summary: This paper describes extraction, identification, and analysis of phenolic compounds from eggplant pulp grown under organic and conventional farming practices. The three phenolic acids (N-caffeoylputrescine, 5-caffeoylquinic acid, and 3-acetyl-5-caffeoylquinic acid) made up the bulk of total eggplant phenolics. In this study, we also report the identification of trace quantities of three additional flavonols, namely, quercetin-3-glucoside, quercetin-3-rhamnoside, and myricetin-3-galactoside from the freeze-dried eggplant pulp. Eggplant extract inhibition of cupric-ion mediated oxidation of low-density lipoproteins was highly correlated with the content of 5-caffeolquinic acid (R2 = 0.9124), the most abundant identified phenolic acid. The data presented in this manuscript will be of interest for the USDA Nutrient Data Lab. Identification and quantification of phenolic phytochemicals will enable researchers to evaluate their roles with relation to diet and health.

Technical Abstract: Increasing interest in natural foods and the environment has resulted in significant demand for organically grown farm products. The present study evaluates the influence that organic and conventional farming practices exert on the phenolic content in eggplant samples belonging to two cultivars, Blackbell (American eggplant) and Millionaire (Japanese eggplant) grown under similar environmental conditions. Phytochemical investigation of the eggplant extracts showed that N-caffeoylputrescine, 5-caffeoylquinic acid, and 3-acetyl-5-caffeoylquinic acid made up the bulk of total eggplant phenolics. In addition, this is the first report on identification of trace quantities of three additional flavonols, namely, quercetin-3-glucoside, quercetin-3-rhamnoside, and myricetin-3-galactoside from the freeze-dried eggplant pulp. The phenolic content of the conventionally grown Blackbell variety were marginally higher or equal to those grown organically. However, the phenolic content of the Millionaire organic variety was much greater than the conventionally grown samples. Eggplant extract inhibition of cupric-ion mediated oxidation of low-density lipoproteins was highly correlated with the content of 5-caffeolquinic acid (R2 = 0.9124), the most abundant identified phenolic acid.