Non-conventional edible plants: Tradescantia zebrina bosse and Althernanthera brasiliana L

The industrial sector is tirelessly searching for more stable and natural colouring food matrices. Considering these demands, the present research investigated the characterization of their most promising compounds in terms of anthocyanin and betalain pigments, followed by the bioactive effect of aqueous extracts obtained from leaves of Tradescantia zebrina Bosse (ETZ) and Alternanthera brasiliana L. (EAB), respectively, with a view to its potential application in the industry. The chemical profile of EAB and ETZ extracts was obtained by HPLC-DAD-ESI/MS. The antioxidant activity of both extracts was evaluated by three different in vitro assays (CAA, reducing power, and DPPH), the antimicrobial activity was tested on a panel of twelve foodborne pathogenic microorganisms and the anti-inflammatory activity was analyzed in rat macrophage cells (RAW 264.7). Finally, cytotoxicity was tested in human tumor cells (MCF-7, NCI-H460, AGS, and CaCo) and toxicity in non-tumor cells (PLP2 and VERO) by the sulforhodamine B method. Two betalain derivatives were found in EAB samples and four anthocyanin derivatives in ETZ samples. The best promising antioxidant activity was showed in DPPH assay (EC50 0.024±0.001 mg/mL, ETZ), followed by reducing power (EC50 0.53±0.01 mg/mL, EAB) and CAA (inhibition: 46% EAB, 62% ETZ, 2000 μg/mL), proving the antioxidant potential of the two extracts. The fungicidal activity of the extracts presented values of ≤ 2 mg/mL, and Bacillus cereus was the most sensitive bacteria, compared to other studied species. Only the EAB extract showed anti-inflammatory activity (IC50 86±3 μg/mL). Promising cytotoxicity results were evidenced, namely for EAB in NCI-H460 tumor cellline (80±8 μg/mL) and for ETZ in AGS tumor cell-line (30±2 μg/mL). None of the extracts showed toxicity for the maximum concentration tested (>400 μg/mL). Thus, it was evident that these plants proved to be a promising alternative for obtaining natural coloring pigments capable of being incorporated into the food industry. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020) and SusTEC (LA/P/0007/2021) and for E.O. PIRES JR. grant (2021.05425.BD) and for M.I. Dias, R.C. Calhelha, and L. Barros contracts. This work is funded by the European Regional Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope of Project GreenHealth - Digital strategies in biological assets to improve well-being and promote green health. info:eu-repo/semantics/publishedVersion