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

[Display omitted] •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. Celtis occidentalis L. (common Hackberry, Cannabaceae) has been applied in the traditional medicine for a long time as a remedy for sore throat, aid during menstruation and for treating jaundice. Nevertheless, the phytochemical exploration of the plant is still incomplete, literature data is limited to flavonoid derivatives isolated from the leaves. The present study reports screening approaches for bioactive compounds in C. occidentalis by fast and simple UHPLC-coupled assays. The UHPLC-DPPH method revealed six constituents in the methanolic extract of the twigs that had not been reported in C. occidentalis before. The antioxidant compounds were isolated by the means of flash chromatography and semi-preparative HPLC and identified by Orbitrap® MS and NMR spectroscopy as N-trans-p-coumaroyloctopamine (1), N-trans-feruloyloctopamine (2), N-trans-caffeoyltyramine (3), 2-trans-3-(4-hydroxyphenyl)-N-[2-(4-hydroxyphenyl)-2-oxoethyl] prop-2-enamide (4), N-trans-p-coumaroyltryramine (5) and N-trans-feruloyltyramine (6). Despite the high antioxidant activity measured in the present study and literature data suggesting potential positive effects of the compounds in the central nervous system, the PAMPA-BBB assay performed with the Celtis extract revealed that none of the aforementioned compounds are able to penetrate across the blood-brain barrier via transcellular passive diffusion.