Isolation and Determination of Four Phenolic Compounds from Peel of Color-fleshed and White-fleshed Potatoes

Potatoes were first introduced outside the Andes region four centuries ago, and have become an integral part of much of the world's food. Potatoes were first introduced into Europe in the 16th century and Korea in the early 19th century. In the nutritional aspects, potatoes contain abundant vitamins and minerals, as well as an assortment of phytochemicals such as carotenoids and natural phenols. chlorogenic acid constitutes up to 90% of potato natural phenols. Due to the high content of potato functional compounds, it has known that potatoes are effective in the prevention of various human diseases. Recently, color-fleshed potatoes ‘Hong-young’ and ‘Ja-young’ were developed by RDA, and it has reported that they have high content of anthocyanin. Additionally they show higher radical scavenging activity compared to white or yellow fleshed potatoes. So it will be expected that the consumption of color-fleshed potatoes gradually increase by pre-peeled potatoes and color potato chips.This study was conducted to enhance the utilization of the peel of color-fleshed potatoes. At first, we isolated four compounds from the organic solvents soluble layer in ethanol extract of peel, and their structures were characterized by spectroscopic methods and by comparing their data to those in the literature. Their structures were characterized to be caffeic acid (1), chlorogenic acid (2), gallic acid (3) and protocatechuic acid (4) for the first time reported from this source. These compounds were already reported ingredients but considered to exhibit a high physiological activity.The quantitative determination on the four compounds in peel of color-fleshed [Hong-young (HY) & Ja-young (JY)] and white-fleshed [Superior (SP)] potatoes samples were measured using HPLC. The concentration of caffeic acid in EtOAc fraction (135.4㎍/g) of SP was higher than in different fractions of HY and JY. The concentration of chlorogenic acid in CHCl3 fraction (299.2㎍/g) of HY was higher than in different fractions of JY and SP. The concentration of gallic acid contents appeared to be highest in BuOH fraction (360.4㎍/g) of JY. The concentration of protocatechuic acid in BuOH fraction (87.1㎍/g) of HY was higher than in different fractions of JY and SP. Overall, color-fleshed potatoes had higher amount of physicochemical properties than ‘Superior’. Therefore, color-fleshed potatoes are expected to be highly valuable items for the development and applications of a functional food. In addition, these results will provide fundamental information for improving sitological value, and breeding of new cultivar.