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9,10-Dihydrophenanthrenes as Phytoalexins of Orchidaceae. Biosynthetic Studies in Vitro and in Vivo Proving the Route From L-phenylalanine to Dihydro-M-Coumaric Acid, Dihydrostilbene and Dihydrophenanthrenes

9,10-Dihydrophenanthrenes as Phytoalexins of Orchidaceae. Biosynthetic Studies in Vitro and in Vivo Proving the Route From L-phenylalanine to Dihydro-M-Coumaric Acid, Dihydrostilbene and Dihydrophenanthrenes

K H Fritzemeier, H Kindl

Eur J Biochem. 1983 Jul 1;133(3):545-50.

PMID: 6861741

Abstract:

Hydroxy derivatives of 9,10-dihydrophenanthrenes, orchinol and hircinol, were isolated from bulbs of Orchidaceae which had been induced to accumulate phytoalexins. Incorporation of radioactive precursors, L-phenylalanine and various hydroxycinnamic acids, has been investigated by feeding experiments in vivo. m-Coumaric acid and dihydro-m-coumaric acid were found to be efficiently incorporated into the dihydrophenanthrene derivatives. Dihydro-m-coumaric acid was not only converted into the dihydrophenanthrenes but was also formed from L-phenylalanine in the same tissue; it was thus proved to be an intermediate. The role of dihydro-m-coumaric acid was substantiated by studies in vitro. An active stilbene synthase was detected in enzyme preparations from induced orchid bulbs and assayed with different CoA esters. The enzyme, characterized on the basis of its substrate specificity, selectively converted dihydro-m-coumaroyl-CoA plus malonyl-CoA into 3,3',5-trihydroxybibenzyl. The role of 3,3',5-trihydroxybibenzyl as physiological intermediate was further corroborated by investigations with intact plants. Both its formation from phenylpropanoids and its conversion into orchinol was demonstrated. The data provided evidence for a biosynthetic sequence originating from L-phenylalanine and leading to 9,10-dihydrophenanthrenes via m-coumaric acid, dihydro-m-coumaric acid, and 3,3',5-trihydroxybibenzyl.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP588307	m-Coumaric acid		588-30-7	Price

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