PURPOSE To study in vitro the antioxidative effect of 6 Satureja montana L. extracts on free radicals and their antiproliferative effect on human tumor cell lines. MATERIALS AND METHODS The antioxidative effect of extracts on 2, 2-diphenyl-1-picryhydrazyl (DPPH) radical was investigated by electron spin resonance (ESR) spectroscopy. Cell growth effect was measured by sulforhodamine B colorimetric assay on HeLa (human cervix epidermoid carcinoma), HT-29 (human colon adenocarcinoma), and MCF-7 (human breast adenocarcinoma) cell lines. IC(50) values were calculated from the concentration response curves following 48 h exposure time. RESULTS The antioxidative activity of extracts increased dose-dependently at mass concentrations ranging from 0.05 to 0.3 mg/ml, and decreased in the following order: n-butanol > methanol > water > ethyl acetate > petroleum ether. All extracts effected cell growth but in a different way, depending on the extract dose and cell line. Extracts exhibited antiproliferative effect on HeLa cell line with IC(50) values ranging from 0.41 to 0.84 mg/ml except petroleum ether (IC(50) >1 mg/ml). Petroleum ether and chloroform extracts stimulated proliferation of HeLa cells within a concentration range from 0.0625 to 0.125 mg/ml. No extract reduced MCF-7 cells growth by 50% even at the concentration of 1 mg/ml. Only petroleum ether and chloroform extracts induced significant growth inhibition of HT-29 cells (IC(50) was approximately 0.74 mg/ml for both extracts). Strong stimulation of HT-29 proliferation was observed within a concentration range from 0.0625 to 0.25 mg/ml for petroleum ether, n-butanol and chloroform extract, and from 0.0625 to 0.5 mg/ml for methanol and water extracts, respectively. CONCLUSION The obtained results indicated that Satureja montana L. extracts are strong antioxidants in vitro. ESR data demonstrated that n-butanol, methanol and water Satureja montana L. extracts possess high antioxidative activity. Chloroform extract did not show any antioxidative activity. Satureja montana L. extracts selectively inhibited the growth of human tumor cells.

Heme reduction of ferric lactoperoxidase (LPO) into its ferrous form initially leads to the accumulation of the unstable form of LPO-Fe(II), which spontaneously converts to a more stable species, the two of which can be identified by Soret peaks at 440 and 434 nm, respectively. Our data demonstrate that both LPO-Fe(II) species are capable of binding O2 at a similar rate to generate the ferrous-dioxy complex. Its formation with respect to O2 was first order and monophasic and with rate constants of kon = 3.8 × 104 m–1 s–1 and koff = 11.2 s–1. The dissociation rate constant for the formation of LPO-Fe(II)-O2 is relatively high, in contrast to hemoprotein model compounds. This high dissociation rate can be attributed to a combination of effects that include the positive trans effect of the proximal ligand, the heme pocket environment, and the geometry of the Fe-O2 linkage. Our results have also shown that the decay of the LPO-Fe(II)-O2 complex occurs by two sequential O2-independent steps. The first step involves formation of a short-lived intermediate that can be characterized by its Soret absorption peak at 416 nm and may be attributed to the weakening of the Fe(II)-O2 linkage with a rate constant of 0.5 s–1. The second step is spontaneous conversion of this intermediate to generate the native enzyme and presumably superoxide as end products with a rate constant of 0.03 s–1. A comprehensive kinetic model that links LPO-Fe(II)-O2 complex formation to the LPO catalase-like activity, combined with the classic catalytic cycle, is presented here.