Synthesis And Biotransformation Of Coumarins By Cambial Meristematic Cells And Dedifferentiated Plant Cells Of Camptotheca Acuminate

Camptotheca acuminate Decne(Nyssaceae) is the family of Camptotheca. Cambial meristematic cells(CMCs) and dedifferentiated plant cells(DDCs) were induced respectively from stem and leaves of C. acuminate. DDCs are dedifferentiated cells, while CMCs are innately undifferentiated and activiely dividing cells. In this article, the differences between CMCs and DDCs were distinguished by the microscopic analysis and their hypersensity to γ-irradiation and radiomimetic drugs. It was confirmed that CMCs from C.acuminate is analogous to plant stem cells.Camptothecin(CPT) and 10-hydroxycamptothecine(HCPT) are the effective components produced by C. acuminate, is the first sccondary metabolite of the biosynthetic pathway, which involve kinds of relevant enzymes and genes. Four key enymes such as tryptophan decarboxylase(TDC), tryptophan synthase(TSB), strictosidine synthase(STR) as well as 3-hydroxy-3-methylglutaryl-coenzyme A reductase(HMGR) and its relavant enzyme genes including tdc1, tdc2, tsb, str, hmg2 and hmg3 were applied to reveal the expression level in CMCs and DDCs from C. acuminate. PCR analysis revealed that tdc2 and str expressed in CMCs2 with surprisingly higher expression level than that in CMCs1 and DDCs.Coumarin is a fragrant organic chemical compound exhibiting diverse biological activity such as antitumor, antifungal, anti-inflammatory and anticoagulant. However, the clinical application of coumarin derivatives was limited due to their insolubility and toxicity, which can be improved by biotransformation. Four coumarins were obtained by Pechmann condensation, named as 7-dihydroxy-4,8-dimethylcoumarin(I), 6-hydroxy-4,7-methylcoumarin(II), 6,7-dihydroxy-4-methylcoumarin(III) and 5-hydroxy-4,7-methylcoumarin(IV), which were transformed by CMCs and DDCs from C.acuminate for the first time. Transformation products were named as 7-O-β-D-glucopyranosyl-4, 8-methylcoumarin(Ia), 6-O-β-D-glucopyranosyl-4,7-methylcoumarin(IIa), 6-hydroxyl-7-methoxy-4-methylcoumarin(IIIa) and 5-O-β-D-glucopyranosyl-4,7-methylcoumarin(IVa). Among them, products named Ia, IIa and IIIa were firstly reported. Furthermore, the optimization of incubation time and the amount of substrate addition were discussed, as well as the activity of monoamine oxidase.