Inhibition of erythrocyte membrane (Na+ + K+)-activated ATPase by ozone-treated phospholipids.
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Ozone-treated aqueous suspensions of natural phospholipids yield at least two types of inhibitors of human erythrocyte membrane (Na+ + K+)-ATPase. The more labile ones appear to be carbonyl-containing substances whose inhibitory properties are enhanced if ozonolysis takes place in the presence of putrescine or glycine. Other amines of similar structure are much less effective as potentiators. Semicarbazide destroys the inhibitory properties of the more labile substances and can release putrescine from the complexes it forms with the carbonyl products of ozonolysis. 3the more stable inhibitors are unaffected by putrescine, glycine, or semicarbazide. Synthetic, saturated phospholipids do not produce these inhibitors during ozonolysis. (+info)
Cytotoxicity of new 5-phenyl-4,5-dihydro-1,3,4-thiadiazole analogues.
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A series of 5-phenyl-4,5-dihydro-1,3,4-thiadiazoles were synthesized and their cytotoxicity was examined against four human cancer cell lines, e.g. lung cancer (A549), ovarian cancer (SK-OV-3), skin cancer (SK-MEL-2), and colon cancer (HCT15). The title compounds were synthesized by condensation of thiosemicarbazide with substituted benzaldehydes, followed by cyclization with acetic anhydrides in good yields. Most of the compounds exhibited significant suppressive activity against the growth of all of the cancer cell lines. The 4-hydroxy analogue of 5-phenyl-4,5-dihydro-1,3,4-thiadiazole (2h) was most active in the inhibition of growth of the SK-MEL-2 cell line, with an IC(50) value of 4.27 microg/ml; followed by compound 2a (IC(50) 5.16 microg/ml). The compounds 2j, 2h, and 2b, bearing 3-methoxy-4-hydroxy-, 4-hydroxy- and 4-methyl substituents in the C-5 phenyl ring respectively, exhibited the highest activity against the SK-OV-3 (IC(50) 7.35 microg/ml), HCT15 (IC(50) 8.25 microg/ml) and A549 (IC(50) 9.40 microg/ml) cell lines, respectively. A structure-activity relationship study revealed that an optimal electron density on the C-5 phenyl ring of 1,3,4-thiadiazoles is crucial for their cytotoxic activity against the human cancer cell lines used in the present study. (+info)