Distribution of free amino acids, flavonoids, total phenolics, and antioxidative activities of jujube (Ziziphus jujuba) fruits and seeds harvested from plants grown in Korea

Authors: CHOI, SUK-HYUN - Seowon University, Korea; AHN, JUN-BAE - Seowon University, Korea; KOZUKUE, NOBUYUKI - Seowon University, Korea; Levin, Carol; Friedman, Mendel

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2011
Publication Date: 5/17/2011
Citation: Choi, S., Ahn, J., Kozukue, N., Levin, C.E., Friedman, M. 2011. Distribution of free amino acids, flavonoids, total phenolics, and antioxidative activities of jujube (Ziziphus jujuba) fruits and seeds harvested from plants grown in Korea. Journal of Agricultural and Food Chemistry. 59:6594-6604.

Interpretive Summary: Fresh, processed, and dried jujube fruit is used as food, mostly in fresh form or as dried dates and confectionary recipes, in bread, cakes, and candy. China produces about 8 million tons of jujube pomace annually. However, their main use seems to be as herbal medicines for the treatment of various ailments, presumably because they have been shown to exhibit numerous health-promoting effects, including antimicrobial activities associated with bioactive phenolic and flavonoid compounds. In addition to bioactive compounds, jujubes also contain nutrients and micronutrients. These include proteins, carbohydrates, vitamins, and minerals as well as free amino acids. Jujubes may therefore be considered as a so-called functional food. In the United States, jujube products are available at health food stores. As part of our studies on antimicrobial activities of so-called health food powders, we are also currently evaluating the antimicrobial potential of jujube powders. The main objectives of this collaborative study with Korean scientists were to determine free amino acid and total phenolic and individual flavonoid content of jujube fruits and seeds from plants grown in Korea and to correlate total phenolic and flavonoid content with antioxidative activities. Because individual jujube flavonoids are reported to exhibit different health-promoting effects, knowledge of the composition of jujube fruits, seeds, and commercial products can benefit consumers.

Technical Abstract: Fruit and seeds from the jujube plant (Ziziphus jujuba) possess nutritional and medicinal including antimicrobial properties. We measured free amino acid content by ion-exchange chromatography, individual phenolic content by HPLC, UV, and mass spectral methods, total phenolic content by Folin-Ciocalteu, and antioxidative activities by two methods in three jujube fruit extracts from Boeun-deachu, Mechu, and Sanzoin cultivars and two seed extracts (Mechu and Sanzoin) harvested from plants grown in Korea. Total free amino acid content (all units in g/100 g dry wt) ranged from 4.0 to 9.7. Total phenolic content ranged from 1.1 to 4.6. Fruits contained the following flavonoids: procyanidin dimeer B2, epicatechin, quercetin-3-rutinoside, quercetine-3-galactoside, kaempferol-glucose-rhamnose, and two unidentified compounds. Seeds contained the following flavonoids: saponarin, spinosin, vitexin, swertish, 6’’’- hydroxybenzoylspinosin, 6’’’-feruoylspinosin, and one unidentified substance. Total flavonoid content of the three fruit samples ranged from 0.7 to 1.8. Total flavonoid content of the two seed samples were 3.2 and 4.0. Phenolic content per g decreased with increasing size of the fruit samples. The distribution of the individual flavonoids among the different samples also varied widely. Results determined by the FRAP antioxidative assay were well correlated with total phenolic content. Because individual jujube flavonoids are reported to exhibit different health-promoting effects, knowledge of the composition of jujube fruits, seeds, and commercial products can benefit consumers. The dietary significance of the results is discussed.