PHENOLIC ACID CONTENT AND COMPOSITION OF EGGPLANT FRUIT IN A GERMPLASM CORE SUBSET

Authors: Stommel, John; Whitaker, Bruce

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2003
Publication Date: 8/25/2003
Citation: Stommel, J.R., Whitaker, B.D. Phenolic acid content and composition of eggplant fruit in a germplasm core subset. Journal of the American Society for Horticultural Science. 2003. V. 128. P. 704-710.

Interpretive Summary: Consumers are being encouraged to eat more fruits and vegetables as a contribution to a balanced diet and because a number of nutrients in produce have been identified that may prevent diseases such as heart disease and cancer. A number of potential health promoting effects have been ascribed to nutrients in plants. The vitamins A, C and E have received considerable attention in this regard because of their antioxidant properties. Some plant phenols that are present in plants are more potent antioxidants than vitamins A, C and E. Eggplant is ranked among the top ten vegetables in terms of its antioxidant capacity. This is due to the fruit phenolic constituents. It is unclear as to how much variation exists among different eggplant cultivars or related wild relatives. We report here an evaluation of phenolics in a diverse collection of 115 eggplants representative of the plants in the USDA eggplant collection. Fourteen different phenolic components were identified and grouped into five different classes based upon their chemical properties. Significant differences in total phenolic content and the types of phenolics present, were evident between the eggplants evaluated. Chlorogenic acid, a type of phenolic, accounted for 96% to 63.4% of total phenolics in most eggplants. Two atypical eggplants exhibited strikingly different phenolic profiles and contained phenolic compounds not evident in other eggplants. Our findings on eggplant fruit phenolics provides opportunities to improve eggplant fruit quality and nutritive value. Our research will be utilized primarily by scientists to develop improved eggplant cultivars and by nutritionists to define eggplant nutritional composition.

Technical Abstract: A number of potential health promoting effects have been ascribed to plant phenolic phytochemicals. We report here a first evaluation of phenolic acid constituents in eggplant fruit from accessions in the USDA eggplant core subset. The core subset includes 101 accessions of the cultivated eggplant, S. melongena, and 14 accessions representing four related eggplant species, S. aethiopicum, S. anguivi, S. incanum, and S. macrocarpon. Significant differences in phenolic acid content and composition were evident among the five eggplant species and among genotypes within species. Fourteen compounds separated by HPLC, that were present in many but not all accessions, were identified as phenolic acids based on HPLC elution times, UV absorbance spectra, ES-MS mass spectral data, and in some cases proton NMR data. These phenolics were grouped into five different classes: chlorogenic acid isomers, isochlorogenic acid isomers, unknown hydroxycinnamic acid and caffeic acid conjugates, and acetylated chlorogenic acid isomers. Total phenolic acid content in S. aethiopicum and S. macrocarpon was low relative to S. melongena. A S. anguivi accession contained the highest phenolic acid content. Chlorogenic acid isomers accounted for 96% to 63.4% of total phenolic acids in most accessions. Two atypical accessions, S. anguivi PI 319855 and S. incanum PI500922, exhibited strikingly different phenolic acid profiles. These PIs also differed from other accessions by the presence of phenolic compounds not evident in other accessions. Our findings on eggplant fruit phenolic content provide opportunities to improve eggplant fruit quality and nutritive value.