Goldenrod Root Compounds Active against Crop Pathogenic Fungi

Root extracts of three goldenrods were screened for antimicrobial compounds. 2Z,8Z- and 2E,8Z-matricaria esters from European goldenrod (Solidago virgaurea) and E- and Z-dehydromatricaria esters from grass-leaved goldenrod (Solidago graminifolia) and first from showy goldenrod (Solidago speciosa) were identified by high-performance thin-layer chromatography combined with effect-directed analysis and high-resolution mass spectrometry or nuclear magnetic resonance spectroscopy after liquid chromatographic fractionation and isolation. Next to their antibacterial effects (against Bacillus subtilis, Aliivibrio fischeri, and Pseudomonas syringae pv. maculicola), they inhibited the crop pathogenic fungi Fusarium avenaceum and Bipolaris sorokiniana with half maximal inhibitory concentrations (IC₅₀) between 31 and 107 μg/mL. Benzyl 2-hydroxy-6-methoxybenzoate, for the first time found in showy goldenrod root, showed the strongest antifungal effect, with IC₅₀ of 25-26 μg/mL for both fungal strains.