Acmella oleracea extracts from in vitro seedlings: chemical characterization and a novel preclinical application on the acute treatment of chemotherapy-induced neuropathy

Acmella oleracea (L.) R.K. Jansen (Asteraceae), popularly known as jambu, is commonly used as food ingredients in typical Amazon cuisine, and as a traditional medicinal herb. It is a rich source of several bioactive compounds, notably alkylamides, flavonoids and other phenolic compounds. The anti-inflammatory, antioxidant, and pain-relieving properties of this plant have been extensively studied, whereas less is known about its properties in the treatment of persistent neuropathic pain. This research involved the study of aerial parts (AP) and roots (R) of Acmella seedlings grown in vitro and developed starting from regenerating lines derived by organogenesis1. The study aimed to characterize the phytochemical profile of the extracts from aerial parts and roots of the plant, focusing on the evaluation of its characteristic secondary metabolites, i.e. alkylamides and phenolic compounds. The compounds were recovered in two extracts: one hydroalcoholic (HAE) and one lipophilic (HE). These extracts were tested on a mouse model of chemotherapy-induced neuropathy (CIN), one of the most debilitating side effects of anti-cancer drugs. A total of 24 compounds (12 phenols and 12 alkylamides) were detected by HPLC-DAD-MS2. The chromatographic profiles of the extracts of the aerial parts and roots showed a similar pattern of secondary metabolites, in particular a pool of cinnamoyl derivatives and several alkylamides, whose main component was spilanthol. The extracts were also analyzed by 1H-NMR spectroscopy to have a fingerprinting of the main organic compounds present in the sample. The two tissues presented quantitative differences in secondary metabolites: the aerial parts were rich in phenols and alkylamides (respectively 8.68 ± 0.31% mg/g DE and 2.77 ± 1.50% mg/g DE in HAE extracts), while the roots were almost twice as rich in phenols (14.15 ± 1.50% mg/g DE in HAE extracts) but alkylamides were in a negligible amount. The extraction and fractionation procedure allowed the separation and concentration of the two classes of secondary metabolites in different extracts for evaluating the biological effect of spilanthol and alkylamides alone or in combination with phenols. Preliminary results on CIN model highlight the acute therapeutic effect of phenolic components of Acmella oleracea aerial parts and roots extracts against oxaliplatin-induced neuropathy, increased by the presence of spilanthol. The results candidate Acmella hydro-alcoholic extracts as a novel approach against neuropathic pain.