The anti-angiogenic effect of polyphenols from the roots of Daphne mucronata Royle subsp. linearifolia (Hart) Halda (Thymelaeaceae)

Abstract

The genus Daphne is an important source of anticancer constituents. In the present study, the Middle-Eastern medicinal plant, Daphne mucronata subsp. Linearifolia, was selected to evaluate its anti-angiogenic and antioxidant activities. Root extracts (n-hexane, chloroform "CHCl 3 ", chloroform/methanol "CHCl 3 /MeOH", and methanol "MeOH") and isolated pure compounds were used to assess the effects on angiogenesis by using an in vivo chorioallantoic membrane (CAM) model. Reversed Phase High Performance Liquid Chromatography "RP-HPLC" analyses were performed on the most active extract to isolate potential anti-angiogenic compounds. The antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay and by measuring the reducing power with a Folin-Ciocalteu reagent. In the CAM model, the CHCl 3 /MeOH extract (100 μg/egg) exhibited a good anti-angiogenic response (37.4% of inhibition) compared with the control group ( p < 0.01). Chromatographic separation of the bioactive extract provided four lignans, the phenylpropanoid glycoside syringin, and two biflavonoids. Syringin and daphnodorin B showed the best anti-angiogenic response on the CAM, inducing a marked reduction of the microvasculature (55.75% and 46.77% of inhibition at 20 μM) and a decrease of haemoglobin content. Additionally, syringin, pinoresinol 4-O-β-D-glucopyranoside, daphnodorin B, lariciresinol 4,4′-bis-O-β-D-glucopyranoside, and genkwanol A revealed a strong antioxidant activity against DPPH radical (IC 50 0.11–0.55 mM) and a good reducing power (2.08–5.32 GAEs). The bio-guided isolation of D. mucronata root CHCl 3 /MeOH extract afforded anti-angiogenic and antioxidant compounds with a potential beneficial role against dangerous and reactive species that were involved in many oxidative stress-related diseases.