Bioguided extraction of phenolic compounds and UHPLC-ESI-Q-TOF-MS/MS characterization of extracts of Moringa oleifera leaves collected in Brazil.

Moringa oleifera leaves are used in Brazilian folk medicine for their hypoglycemic and nutritional properties. In this context, the chemical and biological characteristics were determined. Conventional successive solid-liquid extraction with simultaneous bioguided purification using solvents with different polarities was performed with M. oleifera leaves, yielding six fractions and extracts. The fractions showed better results for antioxidant activity than the extracts. All of them were evaluated by scavenging of synthetic free radicals and reactive oxygen species, and Fr-Ace and Fr-EtOAc showed >100 mg GAE g-1 of phenolic content, while for FRAP and ORAC assays the values were higher than 1600 μmol Fe2+ g-1 and 3500 mmol TEAC g-1 respectively. The UPLC-ESI-QTOF-MS analysis of hydroalcoholic extract (HE) allowed identifying 24 compounds, with flavonoid derivatives being the most abundant group. Furthermore, the alkaloid trigonelline and sesquiterpenoid abscisic acid were identified for the first time in M. oleifera leaves. Finally, gallic acid, caffeic acid, rutin and quercetin were found in concentrations of 16.5, 2129, 477.4 and 127.5 μg g-1 respectively in HE, all of which were higher in fractions and extracts. These results suggest that bioguided extraction is an important technique, due to its ability to concentrate active compounds in a logical and rational way. In addition, M. oleifera leaves grown in Brazil are an important source of phenolic compounds with antioxidant activity that can be used in food, nutraceutical and pharmaceutical products.