Study on the Dynamic Change of Mangiferin and Genkwanin in Aquilaria sinensis Leaves : A New Food Raw Material

Contents of mangiferin and genkwanin were detected by High Performance Liquid Chromatography (HPLC) to explore the dynamic changes of active chemical components from different growing year and different sampling season in Aquilaria sinensis leaves and determine the appropriate growing year and season for sampling. It is disclosed that, growing year was an important influence on content of mangiferin, the appropriate growing year for mangiferin was two to three year and the highest content, 2.31% of mangiferin was in two-year A. sinensis leaves, the appropriate growing year for genkwanin was one to two year and the highest content, 0.23% of genkwanin was in one-year A. sinensis leaves; while the appropriate sampling season for mangiferin was Autumn and the appropriate sampling season for genkwanin was Spring.

Considering their various biological activities, a large quantity of mangiferin and genkwanin are needed for further scientific studies and industrial applications.Dynamic changes of these two active chemical components from different growing year and different sampling season in A. sinensis leaves to determine the appropriate growing year and season for sampling were carried out in this study, to establish the scientific basis for further development of A. sinensis leaves and improve economic benefit of A. sinensis planting industry.
High performance liquid chromatography (HPLC) grade methanol (MeOH) was from Merck Chemical Co.(Darmstadt, Germany); Analytic grade acetic acid (AcOH) and ethanol (MeOH) were purchased from Guangzhou Chemical Reagent Co. (Guangzhou, China).Chemical reference substances of mangiferin and genkwanin were self-made with the purity greater than 98%.
The leaves from of A. sinensis trees cultivated for half year, 1~8 year were collected in different seasons from Zhongshan Agarwood Huang Agroforestry Development Co., Ltd, Zhongshan City, Guangdong Province, China.The plant material was botanically authenticated by Prof. Zhijian Feng in College of Forestry, South China Agricultural University.
Preparation of samples for HPLC test: 1.0 g ovendried leaves of different growing years and seasons of A. sinensis leaves were extracted with 79.5% ethanol 15.0 mL at 80C for 1 h under heating reflux method.After filtration 0.5 mL filtered extract was diluted with 79.5% ethanol to 10 mL to give the samples for HPLC test.

Dynamic change of mangiferin and genkwanin in aquilaria sinensis leaves:
The content detection result of mangiferin and genkwanin from samples of different growing years and different sampling seasons can be seen in Fig. 2 and 3.
From the above data analysis, It is disclosed that, growing year was an important influence on content of mangiferin, the appropriate growing year for mangiferin was two to three year and the highest content, 2.31% of mangiferin was in two-year A. sinensis leaves, while the appropriate growing year for genkwanin was one to two year and the highest content, 0.23% of genkwanin was in one-year A. sinensis leaves.
Sampling season also affected content of mangiferin and genkwanin, the appropriate sampling season for mangiferin was Autumn and the appropriate sampling season for genkwanin was Spring.
In recent agilawood industry, A. sinensis leaves usually be seen as non-medicinal part and discarded after agilawood collection.Such discarded leaves can be used as the raw material to produce active chemical components like mangiferin and genkwanin and the research findings of dynamic change of mangiferin and genkwanin in A. Sinensis leaves in this study can be applied to further greatly reduce the production cost.

CONCLUSION
According to the experimental result of this study, all sample of different growing years collected in different seasons were successfully detected by HPLC.Growing year was an important influence on content of mangiferin, the appropriate growing year for mangiferin and genkwanin in A. sinensis leaves were determined.
Sampling season also affected content of mangiferin and genkwanin, the appropriate sampling season for mangiferin and genkwanin in A. sinensis leaves were determined.

ACKNOWLEDGMENT
Fig. 1: HPLC chromatogram of mangiferin and genkwanin from different growing years; The nethermost chromatogram belong to chemical reference substances of mangiferin or genkwanin and all the rest chromatogram belong to samples from different growing years This research was financially supported by the the Guangdong Provincial Project of Science and Technology (No. 2013B020411003) and the