Mexican arnica anti-inflammatory action:: Plant age is correlated with the concentration of anti-inflammatory sesquiterpenes in the medicinal plant Heterotheca inuloides cass.: (Asteraceae)

Mexican arnica (Heterotheca inuloides Cass.) is a widely used anti-inflammatory medicinal plant in Mexican folk medicine. Although it has been suggested that plant age, fertilization, and harvesting regime influence the concentration of secondary compounds affecting the therapeutic activity of the plant, the effect of these variables on the concentration of the Mexican arnica anti-inflammatory compounds was not known. We quantified anti-inflammatory sesquiterpenes (caryolan-1, 9 beta-diol, cadalen-15-oic acid, 7-hydroxycadalene, 4-hydroxy-2-isopropyl-4, 7-dimethyl-1[4H] naftalinone, 7-hydroxy-4 alpha H-3, 4-dihydrocadalene, beta-caryophyllene, and beta-caryophyllene epoxide) in Mexican arnica plants subjected to fertilization and successive harvests of flowering stems, conditions that mimic the cultivation and harvesting for arnica in Mexico. Fertilization and successive harvesting and their interaction had no significant effect on the concentration of anti-inflammatory compounds. However, the concentrations of these compounds were 60% higher in flowering stems from 15-month-old plants than in those from 4- or 8-month-old plants and was independent of the number of harvests and fertilization regime applied.