Evaluation of the anti-angiogenic activity of saponins from Maesa lanceolata by different assays.

Angiogenesis, in which a vascular network is established from pre-existing vessels, is a complex multistep process. Mechanisms underlying angiogenesis can be investigated using a variety of in vitro, ex vivo and in vivo approaches. Evaluation of several promising plants and plant metabolites, including terpenoids, revealed promising anti-angiogenic activity. Since the maesasaponins displayed anti-angiogenic activity in the chick chorioallantoic membrane (CAM) assay, their activity was further investigated in several test systems. The rat aorta ring assay was compared with the placental vein assay and then selected for the ex vivo investigation of the saponins. Besides their effect on the viability of HUVEC, the anti-angiogenic capacity of the compounds was also investigated in an in vivo zebrafish assay. The activity of the saponins in the viability assay was more pronounced than in the rat aorta ring assay and similar to the effect observed in the CAM assay. The use of different test systems, however, implies different results in the case of saponins.

An ex-vivo angiogenesis assay as a screening method for natural compounds and herbal drug preparations.

Angiogenesis is a fundamental component of complex biological processes, including oncogenesis. The aim of this work was to optimise and validate an ex-vivo angiogenesis assay as a quantitative (PC image) biological method for testing promising natural compounds and herbal drug preparations for their pro-/anti-angiogenic activity. The bioassay is based on the principle of wound healing and quantifies the effect of angiogenic agents on neovessel outgrowth of human placental vessels embedded in a three-dimensional fibrin matrix. The assay was validated by using known, well characterised pro- and anti-angiogenic effectors (basic fibroblast growth factor and carboxyamidotriazole, respectively), and an angiogenesis inhibitor of plant origin (green tea leaves extract) was used as a reference product to demonstrate the applicability of the assay for plant extracts. Other standardised plant extracts prepared from olive tree leaves and horse chestnut seeds were tested for their angiogenic potential, but showed only slight inhibitory or no activity, respectively. The results presented here indicate that this human ex-vivo angiogenic assay is "ready to use" for screening of herbal drug preparations and pure compounds.