Identification of the main phenolic compounds responsible for the antioxidant activity of Litsea glaucescens Kunth

Litsea glaucescens is a native plant from Mexico and Central America known as laurel, and they leaves are commonly used as food seasoning and traditional medicine, however, there is not enough information about its biological activities, as antioxidant and the compounds responsible of this activity. The antioxidant activity and the total phenolic content of a methanolic extract of L. glaucescens leaves (LGE) and a series of twelve chromatographic fractions (I-XII) obtained through a polarity gradient elution are reported in this work. In all the cases a concentration-response was observed since the DPPH inhibition increases (p≤0.05) as a function of the concentration. Nevertheless, the most polar fractions XI and XII were the most effective of the series (100 µg/mL=93 and 91%, 50 µg/mL= 93 and 91%, 25 µg/mL =92 and 87% and 12.5 µg/mL=85 and 53% of radical inhibition, respectively). The results of the FRAP assay confirmed that XI and XII have the highest antioxidant activity (7994.06 and 5011.03 µmol Fe(II)/g, respectively) and the total phenolic content, evaluated by the Folin-Ciocalteu method, was also the highest in both fractions (462.9 and 347.5 mg GAE/g of dry weight, respectively). In addition, epicatechin, was isolated from XI, whereas quercitrin and kaempferol were obtained from XII by flash chromatography and their structures were elucidated through HPLC-ESI-MS and NMR spectroscopy. Then, it is possible to infer that these phenolic compounds are the main responsible for the antioxidant activity of L. glaucescens. Our study provides information that may be useful for the use of this natural product in food and pharmaceutical formulations.