Estudo etnofarmacológico de Kalanchoe daigremontiana Raym. -Hamet & H. Perrier na terapêutica do câncer gástrico: metabolômica, atividade antimutagênica e antitumoral in vitro

Abstract

The medicinal use of plants evolved as an observational, empirical matter, and ancient populations were partial to using herbal remedies to treat illnesses, including cancer. Kalanchoe sp. have traditional medicinal applications and have recently been cited in the literature as having antitumor properties. Kalanchoe daigremontiana (Kd) demonstrates cytotoxic properties on tumor cell lines, including against gastrointestinal tumors. The investigation of the efficacy and safety in the popular use of these natural treatments is essential for the validation of this traditional knowledge through reliable scientific standards. The aim of this study was: (i) to deepen the understanding of the ethnopharmacological importance of Kd; (ii) evaluate a comparative panel of the phytochemical composition of two aqueous extracts obtained, hot and cold, through metabolomic approaches of liquid chromatography coupled to mass spectrometry; (iii) highlight the pharmacological properties of the most abundant compounds in the prepared complex mixture, using in silico approaches; and (v) evaluate the mutagenic potential, (vi) antimutagenic and (vii) antitumor activity in vitro. Aqueous extracts of Kd leafs were obtained by cold (kd1) and hot extractions and independently tested on strains of Salmonella enterica sorovar Typhimurium to assess mutagenicity. The protective capacity of the extracts against DNA damage induced by 4NQO in TA98 and TA100 was evaluated by antimutagenicity assay following models of pre, post and co-exposure. The in vitro antitumor activity against gastrointestinal cancer cells was determined against human hepatocarcinoma (HepG2) and human gastric adenoma (HGC-27) cell lines (as non-tumor control, we used liver stellate cells: FC3H), evaluated by colorimetric water-soluble tetrazolium salt assay. The metabolomics approach revealed a total of 132 metabolites annotated in the Kd extracts. Both extracts showed similar phytochemical composition regarding the number of compounds. Considering the relative abundance, Kd1 had a higher amount of fatty acids and steroids compared to Kd2. 9 phytometabolites in Kd aqueous extracts were predicted (ADMET) to be well absorbed by the gastrointestinal tract and 5 of them showed the best pharmacokinetic and physicochemical profiles, compatible with bioactive compounds or phytopharmaceuticals. Kd extracts are not mutagenic in the Ames test model and are able to protect bacterial cells from mutagenic effects linked to C-G/A-T substitution through intra and extracellular interaction with 4NQO. Kd1 is able to activate the DNA repair system at TA100. In eukaryotic cells, both extracts induced cytotoxic responses in tumor cells, with the Kd1 extract being more selective for HCG-27 cells. Kd1 also showed a better response against tumoral strains. These findings corroborate not only with popular knowledge about this plant but also with data previously published in scientific journals