Guarana: Stability-Indicating RP-HPLC method and safety profile using microglial cells

[Display omitted] •Forced degradation and simultaneous determination of methylxanthines and tannins.•Guarana did not present degradation in acid and oxidative solutions.•Catechins of guarana had epimerization under alkaline conditions.•Guarana was unstable under photochemical conditions.•Guarana may exert a neuroprotective activity. Paullinia cupana Kunth is a compound with therapeutic potential due to the presence of methylxanthines and tannins. In this sense, the precise and safe quantification of these compounds is of fundamental importance. From this, the objective of this work was to develop and validate a stability-indicating RP-HPLC method for the simultaneous determination of theobromine, theophylline, caffeine, catechin and epicatechin in powdered guarana. In addition, the safety profile of guarana exposure in microglia cells was evaluated through different colorimetric and fluorimetric experiments. Chromatographic conditions suitable were obtained using RP-18 column (250 mm × 4.5 mm, 5 μm) at 280 nm. Mobile phase constituted of A: water (0.1 % trifluoroacetic acid pH 4.2) and B: methanol:acetonitrile (25:75 v/v) 90:10 v/v (A:B) at 1 mL.min−1 flow rate. The in vitro tests of cell viability, nitric oxide and formation of total reactive oxygen species levels demonstrated that when in contact with microglia cells, guarana presents safety concentrations of 3.91–15.63 mg.mL−1. The results demonstrated, specificity, linearity, precision, accuracy, and robustness of the proposed method. Based on in vitro tests, it is believed that, in these concentrations, guarana may exert a neuroprotective activity, preventing the activation of microglia, possibly due to the presence of bioactive molecules.