UHPLC-DPPH method reveals antioxidant tyramine and octopamine derivatives in Celtis occidentalis

•UHPLC-DPPH method revealed six antioxidant compounds in Celtis occidentalis twigs.•The constituents were isolated by flash chromatography and semi preparative HPLC.•The compounds were first identified in C. occidentalis by Orbitrap® MS and NMR.•The BBB penetration capability of the compounds was tested by the PAMPA method.•No constituents in the extract were able to cross the BBB via passive diffusion.