Exploring the phytochemical profile and antimicrobial activity of Salvia discolor against phytopathogens

In the present study, we carried out phytochemical characterisation and antimicrobial activity of dichloromethane extract from aerial parts of Salvia discolor Kunth (Lamiaceae). This research aimed to fill the gap in understanding the potential applications of this underexplored species. The dichloromethane extract obtained from the plant surface of S. discolor after repeated chromatographic separation yielded a novel compound with clerodane diterpene skeleton and various known compounds, 8,3’-dihydroxy-6,7,4’-trimethoxyflavone[1], 5,7-dihydroxy-3,4’-dimethoxyflavone[2], divinatorin A[3] and patagonic acid[4], which were identified through spectroscopic NMR analysis, including DEPT, TOCSY, HSQC, HMBC, and ROESY experiments. Furthermore, we assessed the antimicrobial potential of the ground extract against three strains of phytopathogenic bacteria (Clavibacter michiganesis subsp. michiganesis, Pectobacterium carotovorum subsp. carotovorum, Pseudomonas syringae pv. tomato) and nine strains of phytopathogenic fungi (Alternaria solani, Botrytis cinerea, Colletotrichum lindemuthianum, Fusarium solani, Fusarium oxysporum fsp. lactucae race 1, Phoma betae, Phaemoniella chlamydospora, Pythium dissocotum, Stemphylium sp.), selected among the more common pathogens of agricultural interest. Our results showed that the extract was only effective at concentrations above 1000 μg/mL, showing a low antibacterial activity. Conversely, the extract showed a significant antifungal activity against all the fungi tested at different concentrations (100, 250, 500, 750 and 1000 μg/mL). The extract inhibited more than 80% of mycelial growth of F. solani, P. chlamydospora and P. dissotocum, and showed more than 50% inhibition against A. solani, B. cinerea, P. betae and Stemphylium sp. On the other hand, there was minimal inhibition (<30%) against C. lindemuthianum and F. oxysporum fsp. lactucae race 1.