Database dereplication strategy for the targeted isolation of new stilbenoids from the roots of Cyrtopodium paniculatum (Orchidaceae)

Cyrtopodium paniculatum (Ruiz & Pav.) Garay is a terrestrial growing orchid mostly located in South-America [1]. Several related Cyrtopodium species have already been studied for their polysaccharides [2] and stilbenoids content [3], and we herein report the first phytochemical investigation of this neotropical orchid [4]. An extensive investigation of the dichloromethane extract from the C. paniculatum pseudobulbs led to the isolation and identification of 25 stilbenoids (8 of which are newly described). Their structures were elucidated on the basis of spectral and chemical evidences. Both chromatographic and spectrometric data of each compound were collected in the aim of building a stilbenoid database called Orchidatabase. From Orchidatabase, a rapid RP-HPLC-DAD/UV-MS/MS-based dereplication method was established to screen the dichloromethane extracts from the leaves and roots of C. paniculatum to access their chemical profiles and speed up the metabolite identification process [5]. As a result, while the leaves revealed the existence of 9 registered stilbenoids only in traces amount, the roots indicated the presence of 15 major common compounds within the pseudobulbs. Also, additional peaks were observed from the chromatographic profile, which suggested the presence of some unidentified stilbenoids in the dichloromethane root extract. Thus, a targeted fractionation was set up in order to purify those compounds of interest. Ten stilbenoids were isolated using this process and among them, 7 were newly described (Examples shown in the Fig. 1 below). Our metabolomic approach revealed that benzylphenanthrenic compounds were only detected in the pseudobulbs, whereas phenanthrenic dimers seemed to be mostly produced in the underground parts of the plant. Finally, a total of 35 stilbenoids were isolated from C. paniculatum, illustrating the richness of its biosynthetic capacity.

Fig. 1: Chemical structures of 3 new stilbenoids isolated from C. paniculatum roots: cyrtopodinone (1), cyrtopodinol (2) and coeludol A (3)

Keywords: Cyrtopodium paniculatum, Orchidaceae, stilbenoids, Orchidatabase, dereplication strategy.

References:

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