The peroxisome: still a mysterious organelle

More than half a century of research on peroxisomes has revealed unique features of this ubiquitous subcellular organelle, which have often been in disagreement with existing dogmas in cell biology. About 50 peroxisomal enzymes have so far been identified, which contribute to several crucial metabolic processes such as β-oxidation of fatty acids, biosynthesis of ether phospholipids and metabolism of reactive oxygen species, and render peroxisomes indispensable for human health and development. It became obvious that peroxisomes are highly dynamic organelles that rapidly assemble, multiply and degrade in response to metabolic needs. However, many aspects of peroxisome biology are still mysterious. This review addresses recent exciting discoveries on the biogenesis, formation and degradation of peroxisomes, on peroxisomal dynamics and division, as well as on the interaction and cross talk of peroxisomes with other subcellular compartments. Furthermore, recent advances on the role of peroxisomes in medicine and in the identification of novel peroxisomal proteins are discussed

Antiplasmodial activities and cytotoxic effects of aqueous extracts and sesquiterpene lactones from Neurolaena lobata

Aqueous and lipophilic extracts of Neurolaena lobata (Asteraceae), obtained from Guatemala, were tested against Plasmodium falciparum in vitro. Moreover, sesquiterpene lactones, of the germacranolide and furanoheliangolide type, isolated from N. lobata, were shown to be active against P. falciparum in vitro. In addition to their antiplasmodial activity, their cytotoxic effects on human carcinoma cell lines were evaluated. Structure-activity relationships are discussed

Decreased helenalin-induced cytotoxicity by flavonoids from Arnica as studied in a human lung carcinoma cell line

The effect of the flavones apigenin, luteolin, hispidulin and eupafolin, and of the flavonols kaempferol, quercetin, 6-methoxykaempferol and patuletin from Amica spp, on the cytotoxicity of the sesquiterpene lactone helenalin was studied in the human lung carcinoma cell line GLC(4) using the microculture tetrazolium (MTT) assay. The tumour cells were exposed to the test compounds for 2 h. Helenalin concentrations around its control IC50 value, 0.5 mu M, were combined with flavonoid concentrations ranging from 0.01 to 20 mu M. At non-toxic concentrations, up to 10 mu M, all flavonoids except kaempferol significantly reduced the helenalin-induced cytotoxicity. Hispidulin and patuletin displayed their modulating effect on helenalin-induced cytotoxicity in the broadest concentration range. The strongest effect was found with 5 and 10 mu M hispidulin, 0.05 mu M quercetin, and 1 mu M patuletin, increasing the IC50 value of helenalin with circa 40%. No dose-dependency was found in the concentration range tested

Cytotoxicity of flavonoids and sesquiterpene lactones from arnica species against the glc(4) and the colo-320 cell-lines

The cytotoxicity of 21 flavonoids and 5 sesquiterpene lactones, as present in Arnica species, was studied in GLC(4), a human small cell lung carcinoma cell line, and in COLO 320, a human colorectal cancer cell line, using the microculture tetrazolium (MTT) assay. Following continuous incubation, most flavonoids showed moderate to low cytotoxicity, as compared with the reference compound cisplatin (IC50 = 1.1 mu M against GLC(4) and 2.9 mu M against COLO 320). Their IC50 values varied from 17 to > 200 mu M. The most toxic compound was the navone jaceosidin. Of the sesquiterpene lactones tested, helenalin, possessing both the reactive alpha-methylene-gamma-lactone moiety and a reactive alpha,beta-unsubstituted cyclopentenone ring, displayed the strongest cytotoxicity. For 2 h exposure, its IC50 value was 0.44 mu M against GLC(4) and 1.0 mu M against COLO 320. COLO 320 was more sensitive than GLC4 for many flavonoids (especially for flavones), but more resistant to the cytotoxic effect of the sesquiterpene lactones bearing an exocylic methylene group fused to the lactone function