Dimeric phenanthrenoids: possible biogenetic pathway and missing compounds

Secondary metabolites extracted from plants have historically been critical for drug discovery, but their isolation involves expensive and complicated procedures in terms of time and labor resources. Thus, the biogenetic pathway offers the possibility of identifying specific compounds that have not yet been isolated and predicting their isolation from specific natural sources. In plants, biphenanthrenes represent a relatively small group of aromatic secondary metabolites that are considered as important taxonomic markers with promising biological activities. To date, 38 mixed phenanthrenoid dimers have been identified, the biosynthesis of which involves the radical coupling of the two subunits, namely, a phenanthrene and a dihydrophenanthrene. For each of the compounds, it is possible to identify the single phenanthrenic and dihydrophenanthrenic units constituting the considered dimer. Based on the biogenetic pathway, it is possible to identify 19 phenanthrenes and 17 dihydrophenanthrenes, and to distinguish those already known from those not yet isolated. By comparing the results of the possible biosynthetic pathway for each compound with the data in the literature, it is possible to identify three known phenanthrenes and seven known dihydrophenanthrenes, as well as eleven new phenanthrenes and five new dihydrophenanthrenes, and to identify from which plant it is possible to isolate them. This could direct the work of researchers seeking to identify known or new molecules useful for their possible biological properties, and ultimately, to confirm the veracity of the proposed and generally accepted biosynthetic pathway.