Chemical profiling of the urticating trichomes from Cnidoscolus multilobus (“mala mujer”) and their antimicrobial activity

Cnidoscolus multilobus (Pax.) I.M. Johnst (Euphorbiaceae) is a stinging plant widely distributed in the south of Mexico. Currently, chemical and biological properties of the endogenous fluid from the prickles of C. multilobus are still unknown. Thus, the objective of this work was to identify the inflammatory-inducing toxins contained in the prickles of C. multilobus and their possible antimicrobial activity. The chemical identification and quantification of these toxins were carried out by GC-MS and HPLC-DAD. Simultaneously, the endogenous fluid and its most abundant constituents (commercially acquired) were individually tested against opportunistic phytopathogens using the broth microdilution method and XTT antifungal method. According to our results, the fluid contained histamine (17.3-28.4 µg mL-1), dimethylethylamine (1.7-3.6 µg mL-1), acetylcholine (0.6-1.3 µg mL-1), serotonin (24.6-45.8 µg mL-1), oxalic acid (2.2-9.6 µg mL-1) and formic acid (0.9-4.7 µg mL-1). The in vitro growth of Pseudomonas syringae pv. tabaci TBR2004 (MIC, 122.2 µL mL-1), P. syringae pv. tomato DC3000 (MIC, 105.8 µL mL-1), Fusarium oxysporum ATCC 62506 (MIC, 97.4 µL mL-1) and Phytophthora capsici ATCC 15399 (MIC, 163.2 µL mL-1) was inhibited by the fluid. Contrarily, the natural fluid had no effect on the in vitro growth of Clavibacter michiganensis AB299158. The individual assessment of the main compounds dissolved in the fluid revealed that histamine possesses substantial anti-phytopathogenic activity (145.1-219.5 µL mL-1). According to our results, pain-inducing toxins from the prickles of C. multilobus not only are toxic for mammal species, these substances also exhibit inhibitory properties against opportunistic phytopathogens.