Phylligenine, together with quebrachitol, stigmasterol and two aporphine alkaloids—oxoputerine and liriodenine—were isolated from the twigs of Mitrephora vulpina C.E.C. Fisch. They were evaluated for their ability to inhibit platelet activating factor (PAF) receptor binding to rabbit platelets using 3H-PAF as a ligand and their antiplatelet aggregation effect in human whole blood induced by arachidonic acid (AA), collagen and adenosine diphosphate (ADP). Of all the compounds tested, phylligenin and quebrachitol exhibited potent and concentration-dependent inhibitory effects on PAF receptor binding, with IC50 values of 13.1 and 42.2 µM, respectively. The IC50 value of phylligenin was comparable to that of cedrol (10.2 µM), a potent PAF antagonist. Phylligenin also showed strong dose-dependent inhibitory activity on platelet aggregation induced by AA and ADP.
Nine essential oils, hydrodistilled from different parts of five Goniothalamus species (G. velutinus Airy-Shaw, G. woodii Merr., G. clemensii Ban, G. tapis Miq. and G. tapisoides Mat Salleh) were evaluated for their ability to inhibit platelet aggregation in human whole blood using an electrical impedance method and their inhibitory effects on platelet activating factor (PAF) receptor binding with rabbit platelets using 3H-PAF as a ligand. The chemical composition of the oils was analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). The bark oil of G. velutinus was the most effective sample as it inhibited both arachidonic acid (AA) and ADP-induced platelet aggregation with IC50 values of 93.6 and 87.7 µg/mL, respectively. Among the studied oils, the bark oils of G. clemensii, G. woodii, G. velutinus and the root oil of G. tapis showed significant inhibitory effects on PAF receptor binding, with IC50 values ranging from 3.5 to 10.5 µg/mL. The strong PAF antagonistic activity of the active oils is related to their high contents of sesquiterpenes and sesquiterpenoids, and the individual components in the oils could possibly produce a synergistic effect in the overall antiplatelet activity of the oils.
Phytochemical investigation on the bark of Goniothalamus tapis Miq. and G. uvaroides King has resulted in the isolation of eight styryl-lactones, (-)-cryptomeridiol, liriodenine, 3-methyl-1H-benz[f]indole-4,9-dione, (-)-stigmasterol and dimethyl terephthalate. The structures of the compounds were elucidated by spectroscopic techniques. The compounds were evaluated for their effect on platelet-activating factor (PAF) receptor binding on rabbit platelets using (3) H-PAF as a ligand. Among the compounds tested, (-)-cryptomeridiol, (+)-goniothalamin and (+)-isoaltholactone exhibited a significant and concentration-dependent inhibitory effect on PAF receptor binding, with inhibitory concentration (IC)(50) values of 17.5, 19.7 and 46.5 µm, respectively. The inhibitory effects of the first two compounds were comparable to that obtained from the positive control, cedrol. The results indicated that these compounds were strong PAF receptor binding inhibitors.
Sanchezia speciosa, is a bushy shrub from Acanthaceae family which commonly grows in tropical areas of South and Central America. In this study, we employed MTT assay to test the cytotoxicity of that methanolic fraction of S. speciosa leaves on MCF-7 human breast cancer, SK-MEL-5 human malignant melanoma and human umbilical vein endothelial cells, HUVEC cells. The extract showed highest activity on MCF-7 and moderate cytotoxicity towards SK-MEL-5. In contrast, the extract demonstrated lowest cell growth inhibition activity on HUVEC cells, indicating better selectivity compare to standard drug, doxorubicin. In addition, we also performed ORAC assay to determine the radical scavenging capacity of methanolic extract of S. speciosa leaves. The extract exhibited nearly similar anti-oxidant activity as quercetin, suggesting S. speciosa leaves as a potential source of natural anti-oxidant. To the best of our knowledge, this is the first report on anti-oxidant and cytotoxic activity of S. speciosa.
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