Anti-angiogenic and cytotoxicity studies of some medicinal plants.

Angiogenesis plays an important role in tumor formation and proliferation. The development of anti-angiogenic agents to block new blood vessel growth will inhibit metastasis and induce apoptosis of the cancer cells. Nine medicinal plants, Strobilanthes crispus, Phyllanthus niruri, Phyllanthus pulcher, Phyllanthus urinaria, Ailanthus malabarica, Irvingia malayana, Smilax myosotiflora, Tinospora crispa and blumea balsamifera were screened for anti-angiogenic properties using the rat aortic ring assay. Of these, the methanol extracts of Phyllanthus species and Irvingia malayana exhibited the highest activity. At 100 microg/mL, P. pulcher, P. niruri, P. urinaria and I. malayana recorded an inhibition of 78.8 %, 59.5 %, 56.7 % and 46.4 %, respectively, against rat aortic vascular growth. Their activities were further investigated by the tube formation assay involving human umbilical vein endothelial cells (HUVEC) on Matrigel. I. malayana, P. niruri and P. urinaria showed a significant decrease of 45.5, 37.9 and 35.6 %, respectively, whilst P. pulcher showed a much lower decrease of 15.5 % when compared with that of the rat aortic ring assay. All the plant extracts were evaluated for cytotoxicity on a panel of human cancer cell lines using the MTT assay. None of them displayed acute cytotoxicity. The HPLC of P. niruri, P. urinaria and P. pulcher indicated the extracts contained some identical chromatographic peaks of lignans. Further fractionation of I. malayana yielded betulinic acid reported in this plant for the first time and at 100 microg/mL it exhibited a 67.3 % inhibition of vessel outgrowth and 46.5 % inhibition of tube formation.