ElsevierGisbert Domenech, MC.; Prohens Tomás, J.; Raigón Jiménez, MD.; Stommel, J.; Nuez Viñals, F. (2011). Eggplant relatives as sources of variation for developing new rootstocks: effects of grafting on eggplant yield and fruit apparent quality and composition. Scientia Horticulturae. 128(1): 14-22. doi:10.1016/j.scienta.2010.12

There is gathering evidence that antioxidant phytonutrients in fruits and vegetables have health-promoting effects. Eggplant fruit have a high content of antioxidant phenolic compounds. We evaluated the main class of eggplant phenolics, hydroxycinnamic acid conjugates, in the fruit of seven commercial cultivars. Fourteen conjugates were quantified and identified by high-performance liquid chromatography, ES(-)-MS, and (1)H NMR data. Significant differences in their content and composition were evident among cultivars and in tissue from stem, middle, and blossom end segments. Chlorogenic acid (5-O-caffeoylquinic acid) was the predominant compound, and its 3-O-, 4-O-, and 5-O-cis isomers were also present. The 10 other phenolics fell into four groups, including 3,5- and 4,5-dicaffeoylquinic acid isomers, four amide conjugates, two unknown caffeic acid conjugates, and 3-O-acetyl esters of 5-O- and 4-O-caffeoylquinic acid. Dicaffeoylquinic and 3-O-acetyl chlorogenic acids were most variable among the cultivars. Dicaffeoyquinic acids were most abundant in the blossom end, whereas 3-O-acetyl esters were highest in the midsection.

Eggplant (Solanum melongena L.) is ranked among the top ten vegetables in terms of oxygen radical absorbance capacity due to its fruit's phenolic constituents. Several 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 L., S. anguivi Lam., S. incanum L., and S. macrocarpon L. 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 or tentatively identified as hydroxycinnamic acid (HCA) derivatives based on HPLC elution times, UV absorbance spectra, ES-—MS mass spectra, and in some cases proton NMR data. These phenolics were grouped into five classes: chlorogenic acid isomers, isochlorogenic acid isomers, hydroxycinnamic acid amide conjugates, unidentified caffeic acid conjugates, and acetylated chlorogenic acid isomers. Among S. melongena accessions, there was a nearly 20-fold range in total HCA content. Total HCA content in S. aethiopicum and S. macrocarpon was low relative to S. melongena. A S. anguivi accession had the highest HCA content among core subset accessions. Chlorogenic acid isomers ranged from 63.4% to 96% of total HCAs in most core accessions. Two atypical accessions, S. anguivi PI 319855 and S. incanum PI500922, exhibited strikingly different HCA conjugate profiles, which differed from those of all other core subset accessions by the presence of several unique phenolic compounds. Our findings on eggplant fruit phenolic content provide opportunities to improve eggplant fruit quality and nutritive value.