The Metabolic Pathway Of Anthocyanin And Its Metabolites In Malus Crabapples

Malus crabapples, belongs to the genus Malus Mill. of the family Rosaceae, with fruit no more than 5cm in diameter, could be divided into three kinds (ever-green-leaf cultivar'Flame'; young-red-leaf-mature-green-leaf cultivar'Radiant'; ever-mauve-leaf cultivar'Royalty') according to leaves'colour, three kinds according to flowers'colour, and two kinds according to fruits'colour. Malus crabapples, which have graceful tree performance, species diversity and colourful leaves, flowers and fruits, are promising fruit trees for olemental, edible, process and medicinal utilizations.Anthocyanins are water-soluble flavonoid pigments that can be found in most higher plants and are responsible for the colour of leaves, flowers, fruits and seeds. In nature, the anthocyanins commonly combine with glucosides. The different anthocyanins exhibit diverse colors. Anthocyanin biosynthesis is on of the branch of the flavonoid pathways. In plants, flavonoids are synthesized by the anthocyanin biosynthesis. The biosynthesis of anthocyanin is controled by different factors and the activity of enzyme is one of the most important ones.Because of the difference in contents and kinds of anthocyanins in Malus crabapples, their colours of leaf and flower are different. And the different flavonoid contents and kinds influences the flavor of fruits of Malus crabapples.In this study, we used three Malus crabapple cultivars as the plant materials which have various colours of leaf and flower, and detected the colours of each cultivars by colour-difference meter. We also detected the functional components (anthocyanins) and active components (flavonoids) by HPLC and HPLC-DAD-MS. In addition, the enzyme activity which regulate the biosynthesis of anthocyanin in Malus crabapples were assayed. The results showed that the different colours in leaves and flowers of various Malus crabapple cultivars were caused by different anthocyanins. The'Royalty'(ever-mauve-leaf cultivar) has the maximum anthocyanins in the leaves and flowers, and the main components are cyanidin-3-O-glucoside and cyanidin-3-o-arabinose. The anthocyanins contents in'Radiant' (young-red-leaf-Mature-green-leaf cultivar) are lower than'Royalty'and the main components are cyanidin-3-O-glucoside and pelargonidin-3-O-glucoside. We found no anthocyanins in'Flame' (ever-green-leaf cultivar).In addition, our results showed that different Malus crabapple cultivars contained different flavonoids. We detected three apigenins, two kaempferols, four quercetins, one rutin, catechin, and phloridzin respectively in the three Malus crabapple cultivars. The contents of kaempferols and quercetins in different parts of'Royalty'and'Radiant'are much higher than'Flame'and the contents of catechins and phloridzins are much higher in different parts of'Flame'. We also assayed activities of several enzymes in the biosynthesis passway of anthocyanin and the results showed that the Flavanone-3-hydroxylase (F3H) is the key enzyme in anthocyanin biosynthesis. On the basis of the results obtained, the anthocyanin biosynthetic pathway of Malus crabapples were hypothesized.