Metabolite profiling of "Eretto Liguria", an Italian local ecotype of Salvia rosmarinus, and antimicrobial activity against Pectobacterium carotovorum subsp. carotovorum

A targeted NMR metabolomic approach was used to characterise Salvia rosmarinus “Eretto Liguria” ecotype, commonly used in Northwest Italy by farmers for cuttings and for marketing, with a view to application and registration processes for designation of protected geographical indications. Quali- quantitative NMR based investigation was perfomed by means of Chenomx (Chenomx NMR Suite 8.6, Chenomx Inc., Edmonton, 252 Canada) and NMRProcFlow tools, and was followed by multivariate data analysis. Self-organising maps (SOMs) showed that the accessions of “Eretto Liguria” appeared well characterised compared to the other commercial cultivars and ecotypes from the same geographical region, and had a good content in carnosic acid. Moreover, to evaluate the possibility of using the rosemary biomass, after the removal of cuttings or fronds marketable as flavouring, as a source of extracts and pure compounds with potential phytosanitary activity in organic farming, rosemary methanolic extracts and the pure abietane compounds were tested for their ability to reduce the pectolytic activity of the soft rotting P. carotovorum subsp. carotovorum on potato tissue. The in vitro assay on potato tuber slices showed the ability of rosemary methanolic extracts to reduce the pectolytic activity, and 7-O-methylrosmanol, carnosol and isorosmanol were showed to completely inhibit the pectolytic activity. In silico studies showed that these abietane diterpenoids may interact with P. carotovorum subsp. carotovorum pectinase enzymes (pectate lyase 1 and endopolygalacturonase), thus highlighting these rosemary components as starting points for the development of agents able to prevent soft rot progression in potato crops.