| Objective:To examine the antimicrobial activity of Laurencia extract; and to investigate the antitumor activity of Laurencia extract against breast carcinoma induced by DMBA in rats, and on depressing proliferation of Hela (cervical carcinoma) and HT-29 (large intestine carcinoma) cell lines.Methods: 1. Escherichia coli., staphylococcus aureus and Streptococcus spp were inoculated in agar gel, and dry aseptic papers immerged in Laurencia extract were put on the surface of the plates and had been incubated for 18h. The cycle of bacteria growth inhibition were measured in the diameter abound paper disc.2. Seventy-five female Wistar rats were randomly divided into five groups and were daily given 25mg/kg·bw(A group),50mg/kg·bw (B group), 100mg/kg·bw (C group) Laurencia extract, and salad oil for both D and E groups. The most of rats in A, B, C and D groups would suffer from breast cancer induced by DMBA, a carcinogen, and those in E group were free from DMBA during 16 week treatment. Then all rats were painlessly killed at that time. The sample of the blood were collected, and the fresh tumor, thymus and spleen were seperated and weighed. The letvels of malanydiadehyde (MDA), and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in plasma were measured by biochemical methods with the kits.3. The proliferation of Hela and HT-29 cell lines were determinated by MTT assay.Results: 1 .The cycle of bacterial growth inhibition paper disc immerged with Laurencia extract on staphylococcus aureus was the same size as the diameter of Benzylpenicillin, while the effects of Laurencia extract on inhibiting other two kinds of bacteria were not found.2. The incidence of breast cancer in rats of the A, B and C groups supplemented with Laurencia extract were 66.7%, 60.0% and 40.0% respectively; which were lower than that (80.0%) in rats of group D, and the incidence was lower in group C than group D as well (p<0.05). The average amount of fresh tumor weighted was lower in all four groups than D group. After 16 week supplementation with Laurencia extract, the rates of tumor growth inhibition were 36.57% , 52.15% and 56.30% in the A, B and C groups, respectively. The indexs of spleen in the C group and the thymus in the A group were higher than D group(p<0.05) . Moreover, the activities of SOD in the A and E groups significantly increased (P<0.01), compared with the D group, and the activity of GSH-Px in the E group was higher than the C and D groups(P<0.05); while compared with D group the Laurencia extractvels of plasma MDA were significantly decreased in both A, E groups (P<0.05) and C,D groups(P<0.01).3. The IC50 of Laurencia bromine-sesquiterpene on Hela cell for 48h and 72h were 46.8μg/mL and47.5μg/ML., and on HT-29 cell for 48h and 96h, IC50 were 51 .7μg/mL and 35.9μg/mL. Conclusions: The Laurencia extract exhibited antibacteral activity against the growth of...
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