Quantitative Changes of Polyphenolic Compounds in Mulberry (Morus alba L.) Leaves in Relation to Varieties, Harvest Period, and Heat Processing.
Six polyphenolic compounds, such as chlorogenic acid (CA), rutin (RT), isoquercitrin (IQT), quercetin-3-O-(6-O-malonyl)-β-D-glucoside (QMG), astragalin (AG), kaempferol-3-O-(6-O-malonyl)-β-D-glucoside (KMG), were isolated from mulberry leaves by a series of isolation procedures, such as Diaion HP-20, silica-gel, Sephadex LH-20, and ODS-A column chromatographies. The chemical structures of the phenolic compounds were identified by UV and NMR spectral analyses. Levels of polyphenols in mulberry leaves from six different mulberry cultivars ranged from 1,042.16 to 1,871.97 mg% per dry weight; Guksang cultivar showed the highest levels of polyphenols, whereas Gaeryangdaehwa contained the least polyphenol contents. Generally, levels of polyphenols in mulberry leaves decreased with increasing harvest time, except for Yoolmok, but increased with heat processing time, except QMG and KMG. These results suggest that the heat processed mulberry leaves of Guksang cultivar harvested in early May can be potentially useful sources for production of high quality mulberry leaf teas.
Department of Food Science and Nutrition, Catholic University of Daegu, Gyeongbuk 712-702, Korea.
Won Jeong
WJ
Lee
Department of Food Science and Nutrition, Catholic University of Daegu, Gyeongbuk 712-702, Korea.
Sang Won
SW
Choi
cultivars; harvest time; heat processing; mulberry (Morus alba) leaf; polyphenols