Verbascoside and luteolin-5-O-β-d-glucoside isolated from Halleria lucida L. exhibit antagonistic anti-oxidant properties in vitro

The purpose of this investigation was to determine and characterise the anti-oxidant activity of the methanol extract of the leaves of Halleria lucida utilizing the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay. The methanol extract of the leaves of H. lucida displayed promising anti-oxidant activity with an IC50 value of 8.49 ± 0.12 μg/ml and was subsequently subjected to activity-guided fractionation resulting in the isolation of a flavone-type flavonoid and phenylpropanoid glycoside, namely luteolin-5-O-β-d-glucoside and verbascoside (acteoside), respectively. Both compounds displayed promising anti-oxidant activities with IC50 values of 6.12 ± 0.40 and 7.18 ± 0.08 μg/ml for luteolin-5-O-β-d-glucoside and verbascoside, respectively. Furthermore, isobologram construction was undertaken to determine pharmacological interactions between the isolated molecules resulting in a concentration-dependent additive and antagonistic interaction being recognised.