Study On The Variation Pattern Of Main Functional Components In Different Strains Of Dendrobium Officinale Leaves

To provide scientific basis for the variety breeding and expanding of medicinal or edible parts, this paper revealed the variations of functional constituents and antioxidant capacity among different strains and harvest periods for Dendrobium officinale leaves, and achieved the following results:1. The content of polysaccharides in D.officinale leaves was 4.45~12.17%, and was about a quarter in stems. The alcohol-soluble extracts content in leaves was 7.45~29.34%, and was 1.5 times that of stems. The quality variation of polysaccharides in leaves was closely related to the phenophase. The leaves with lower level of metabolism in three stages: winter, early of germination stage and deciduous period, which led to lower content of polysaccharides. The leaves at the vigorous growth stage with higher content of polysaccharides. The alcohol-soluble extracts were closely associated to the formation and germination of buds. The content of alcohol-soluble extracts peaked before sprout, that provided the material basis for the growth of new shoots. There were differences in the accumulation regularity of D. officinale polysaccharides between leaves and stems, but similar in alcohol-soluble extracts.2. The total amino acids content of leaves was from 6.76 to 7.97 g·100g-1. As the content of amino acids in leaves was significantly higher than stems, and the composition was close to the ideal protein standard proposed by FAO/WHO, leaves of D.officinale had a good prospect for the development of functional foods. The 9×66 strain which with high yield and polysaccharide content had highest amino acids content both in stems and in leaves, indicated crossbreeding could improve the quality of varieties. Compared the amino acids content of D.officinale in two main harvest periods, the harvest time has a significant impact on amino acids content of D.officinale. This study demonstrates that the harvesting time of D.officinale stems was suitable for leaves as well, which is the period before bolssom.3. The content of total flavonoid in D.officinale leaves was positively correlated with the ability of DPPH free radical scavenging. The HPLC Chromatograms of 11 D.officinale strains leaves showed that there was significant difference in composition and content of flavonoids for 11 D.officinale strains leaves. Leaves collected in different harvest periods has significant difference in total flavonoids contents, the dynamic variation of total flavonoids contents in three strains collected in 12 harvest period was consistent. Phenophase have significant effect on the total flavonoids content, the contents of three strains in January(before germination) were highest. The total flavonoids accumulation promoted growth and development of D.officinale. The average total flavonoid content of three strains harvested before bud was 11.68 mg·g-1. Based on the content of flavonoids and other chemical components, 9×66 strains have higher medicinal value for development.4. According to the results of the main chemical constituents content and antioxidant activity of D.officinale leaf, 3 superior strains(6A×2B、9×66 and 78×69) were selected. The reasonable harvest time for D.officinale was that harvesting before flowering could obtain more polysaccharides and amino acids, and harvesting before sprout could obtain more alcohol-soluble extracts and flavonoids. The harvesting time of D.officinale stems was suitable for leaves.