Seasonal variations of metabolite content in phloem sap from broussonetia papyrifera

Phloem sap not only services important physiological function in tree growth but also can be selected for a potential raw material in chemical industrial products. As a tree species from Moraceae, Broussonetia papyrifera (BP) contains rich phloem sap.In order to investigate the phloem sap content and the variation during tree growh, Gas chromatography-mass spectrometry was employed to analyze the metabolites in phloem sap of BP, with a focus on seasonal variations in metabolite content. A total of 38 metabolites were detected in BP phloem exudates, with the highest content (44.59mg g-1) of total metabolites observed in March. Moreover, large amounts of organic acids and sugars were detected in BP phloem exudates for all growing months, as well as lower amounts of fatty acids and alcohols. Metabolites associated with anticancer and anti-inflammation properties (e.g. PI3 kinase inhibitor, Chlorogenic acid, Chelerythrine and palmitic acid) were also detected. Quininic acid was the most abundant organic acid, representing up to 86.3% of all organic acids. In addition, D-fructose, D-glucose, and sucrose were the principle soluble sugars observed in phloem saps, with a maximum sugar content of 19.76mg g-1 in November. Seasonal changes in the metabolite content varied among individuals. Results of the metabolite analysis confirmed the role of BP phloem sap as an important resource for the synthesis of both pharmaceutical and human health products. All the results suggested that phloem sap content changes with the tree growth season. (author)