Cytotoxic constituents in the holdfast of cultivated Laminaria japonica

ABSTRACT:     Four steroidal ketones were isolated from the holdfast of cultivated Laminaria japonica . The structures were characterized as ergosta-4,24(28)-diene-3-one (1), ergosta-4,24(28)-diene-3,6-dione (2), stigmasta-4,24(28)-diene-3-one (3) and stigmasta-4,24(28)-diene-3,6-dione (4), by spectral data. Compounds 2 and 4 were shown to be cytotoxic against the MCF-7 human breast cancer cell, and the growth of MCF-7 was inhibited by 96% and 79%, respectively, at 10 µg/mL. It is the first report on the isolation of cytotoxic steroidal ketones from the kelp in the genus of Laminaria.     

Effects of Azolla species on weed emergence in a rice paddy ecosystem

The effects of Azolla pinnata R. Br. on weed emergence were evaluated in terms of plot area coverage by an A. pinnata mat, its biomass production and the amount of weed emergence, using fresh and dry weights, in a rice paddy field experiment. The experiment was conducted following a randomized block design with five combinations of fertilizer and A. pinnata treatments (control, A. pinnata  + superphosphate, A. pinnata  + urea, A. pinnata  + compound fertilizer, A. pinnata  + cow manure). The results revealed that after 18 days of inoculation, all superphosphate (T1) and cow manure (T4)-treated plots were fully covered by the A. pinnata mat. However, coverage of the urea (T2) and compound fertilizer (T3)-treated plots were only 80% and 70%, respectively. The full plot area coverage by the A. pinnata mat and the highest biomass production with superphosphate and cow manure-treated plots were able to completely inhibit two weed species ( Scirpus juncoides Roxb. var. hotarui Ohwi and Monochoria vaginalis Burm. f. Presl var. plantaginea (Roxb.) Solms-Laub) and significantly suppressed four other weeds ( Cyperus serotinus Rottb, Echinochla oryzicola Vasing, and Eclipta prostrata L.). In all the treatments, the fresh weight of weeds significantly reduced to 13, 29, 34, and 9%, respectively, for treatments T1, T2, T3, and T4. The dry weights also were significantly reduced to 10.00, 16.00, 22.00, and 7.26%, respectively, for treatments T1, T2, T3, and T4 over the control. The results revealed that there was a significant correlation among plot area coverage by the A. pinnata mat, its biomass production and weed emergence in a rice paddy field over the control. Azolla pinnata did not have any detrimental effect on the growth of rice plants.