Genetic alterations for increased coumarin production lead to metabolic changes in the medicinally important Pelargonium sidoides DC (Geraniaceae)

The medicinal plant Pelargonium sidoides is fast becoming threatened due to the overharvest of its tubers from the wild to produce a phytopharmaceutical for treating respiratory infections. The action of the coumarins is implicated in the efficacy of the commercial herbal extract with the highly oxygenated coumarins exhibiting the best anti-bacterial and anti-viral activity. Through this work we aimed at exploring the metabolic effects of Agrobacterium rhizogenes transformation. After confirmation of transgenesis using PCR amplification of the rol A (320 bp), rol B (400 bp) and rol C (600 bp) genes, metabolite profiles indicated a high level of variability between the different transgenic clones but these had more compounds compared to non-transgenic control cultures. This was represented by a two- to four-fold increase in detected metabolites in transgenic clones. We quantified several commercially important coumarins, flavonoids and phenolic acids. One of the clones had six out of nine of these metabolites. Overall, the concentration of these metabolites of interest were significantly changed in transgenic root cultures, for instance shikimic acid was recorded at the highest level in clone A4T-A. Production of key metabolites at significantly higher concentrations due to transgenesis and positive anti-bacterial activity exhibited by transgenic roots lends support to the idea of developing these clones as an alternative source that will allow for sustainable access to economically valuable secondary compounds of P. sidoides.