Response to Commentary: Arnica montana Effects on Gene Expression in a Human Macrophage Cell Line. Evaluation by Quantitative Real-Time PCR.

We recently investigated the effects of Arnica montana (Arnica) on the THP-1 myelomonocytic cell line, differentiated by phorbol-myristate acetate and IL-4 in the wound healing phenotype (M2) (1). Our study was the object of a commentary by Chirumbolo and Bjorklund (2), based on some recalculations and on their extrapolations from the values of SEM. Even though we had correctly reported the dosage of sesquiterpenes – reference substances for Arnica pharmacopeia – the authors inferred that this information was insufficient and they recalculated the doses in terms of helenalin: “in the starting 30% alcoholic preparation of Arnica (1c), a percentage of 0.036% sesquiterpene lactones, should correspond to 0.72 μg, i.e., 72 ng in the dilution 2c.” This calculation is flawed because our dose was referred to the mother tincture and not to the 1c dilution. Moreover, helenalin is not the only active ingredient in Arnica, which contains many other substances (3, 4). Finally, 0.72 μg in 1c are not 72 ng in 2c but 7.2 ng.