Chemical constituents, antioxidant potential, antibacterial study and photoprotective activity of Brazilian corn silk extract

Abstract

The aim of this work was to determine the total phenolic content and evaluate the antioxidant, antibacterial, photoprotective and cytotoxic properties of corn silk ethanol extract prepared from corn silk that was air-dried at room temperature. Corn silk ethanol extract has a high content of phenolic compounds. The concentrations of ethanol extract required to produce 50% of maximal effect (EC₅₀) in DPPH and ABTS radical scavenging assays were 489.0 and 166.1 µg/mL respectively, indicating low activity when compared to the positive control. The ethanolic extract of corn silk showed antibacterial activity, mainly on Gram-positive bacteria. The in vitro sun protection factor (SPF) of the ethanolic extract of corn silk incorporated into sunscreen UVA-UVB 5% gel with Pemulen TR-1® was evaluated for the first time. A relative increase in SPF efficacy was observed for the extract when the sunscreen was incorporated. The ethanolic extract of corn silk and the gel were considered non-cytotoxic. The corn silk ethanolic extract was characterized using ultra performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS). Eleven compounds including flavonoids, coumaric acid derivatives, terpenoid, hydroxycinnamic acid derivative and quinic acid derivative were suggested based on their accurate mass and MS/MS spectra.

Keywords:
corn silk; ethanol extract; phenolic compounds; sun protection factor; sunscreen UVA-UVB 5% gel with Pemulen TR-1