Powdered tissue from 46 species of air-dried marine algae (four green, 21 brown and 21 red algae) were screened for antitumor activity . Significant activity against Ehrlich carcinoma was found in the brown algae Scytosiphon lomentaria (69.8 % inhibition), Lessonia nigrescens (60 .0 %), Laminaria japonica (57.6 %), Sargassum ringgoldianum (46.5%), the red algae Porphyra yezoensis (53 .2%) and Eucheuma gelatinae (52.1 %) and the green alga Enteromorpha prolifera (51 .7 %) . Five brown and four red algae showed appreciable antitumor activity against Meth-A fibrosarcoma . To identify specific molecules with antitumor activity, 15 kinds of polysaccharide preparations of seaweed origin and 24 kinds of lipid fractions extracted from various seaweeds were tested . Appreciable inhibition of Ehrlich carcinoma was found for fucoidan preparations from Undaria pinnatifida and Sargassum ringgoldianum, for carrageenans and for porphyran . Several glycolipid and phospholipid fractions from brown and red algae were effective against Meth-A fibrosarcoma.

For elucidation of the entity of antitumour activity of marine algae, 17 kinds of polysaccharide preparations of seaweed origin and 24 kinds of lipid fractions extracted from various seaweeds were selected as experimental material in addition to pectin. Mice implanted with Ehrlich car cinoma and Meth A fibrosarcoma were used as assay animal. Appreciable inhibition of tumour growth was found for fucoidan preparations form Undaria pinnatifida and Sargassum ringgoldianum, carrageenans and porphyran, being 51.7-54.5, 78.1, 40.1-54.0, and 45.3-58.4 %, respectively. The antitumour activities of lipid fractions against Meth A fibrosarcoma were found to be 36.1-47.1% with all the 3 fractions from S. ringgoldianum, and those of glycolipid and phospholipid fractions from L. angustata were as high as 45.9 and 58.0%, the latter of which was obtained from nearly 1/6 amount of injection. Phospholipid fraction from P. yezoensis showed very high activity such as 64.0% which was the value at the injection of nearly the same amounts as above, and it was the highest value among all the fractions tested in this work.

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The red rot disease of Porphyra yezoensis Ueda (Rhodophyta) is caused by a parasitic fungus, Pythium sp. To facilitate the detection of this pathogen in infected thalli of P. yezoensis, polyclonal and monoclonal antibodies were prepared. Antibodies were raised against antigen prepared from an isolate of fungal hyphae obtained from red-rot infected thallus of P. yezoensis from Aichi Prefecture. Polyclonal antibody was obtained from the antisera of immunized rabbits. Monoclonal antibody was obtained from the culture supernatant of a hybridoma which had been established by cell fusion between a myeloma cell line and spleen cells of immunized mice. Hyphae were detected by means of indirect fluorescent antibody technique. Titers of polyclonal antibodies obtained were too low to recognize fungal hyphae that had penetrated the thalli of P yezoensis; however, monoclonal antibody was useful for the detection of fungi that had penetrated algal thalli. The monoclonal antibody was specific for the Pythium sp. from red-rot infected thalli of P. yezoensis from Saga (western Japan) and from Aichi Prefectures (central Japan), but was ineffective for infections from Miyagi Prefecture (northern Japan). It is evident, therefore, that Pythium sp. can give rise to immunologically distinct groups of red rot disease. Based on chemical and enzymatic treatments, the antigenic determinant appeared to localize on the sugar chains of glycoconjugates or the polysaccharides of the hyphal cell wall.

Screening of antitumour activities were performed by using 56 species of marine algae (4 green, 24 brown, and 28 red algae) from the viewpoint of possible utilization for tumour preventing material. After the preoral administration of powdered 57 species of marine plants for 14 days, mice were inoculated with Ehrlich carcinoma, and breeding was continued for further 14 days. It was found that 3 green, 8 brown, 5 red algae and Z. marina show appreciable antitumour activity. Of the marine algae Scytosiphon lomentaria (Phaeophyta) showed the higherst inhibition rate (69.8%), followed by Lessonia nigrescens (60.0%, Phaeophyta), Laminaria japonica (57.6%, Phaeophyta), Porphyra yezoensis (53.2%, Rhodophyta), Eucheum gelatinae (52.1%, Rhodophyta), Entero morpha prolifera (51.7%, Chlorophyta) and Sargassum ringgoldianum (46.5%, Phaeophyta).When 24 kinds of seaweed powder samples (2 green, 13 brown, and 9 red algae) were admin istered intraperitoneally 7 times during 21 days to mice inoculated with Meth A fibrosarcoma, 5 brown and 4 red algae showed appreciable antitumour activities. The inhibition rates were the highest in Sargassum patens (55.5%, Phaeophyta) followed by Eucheuma cottonii (39.8%, Rhodo phyta), S. ringgoldianum (39.1%, Phyaeophyta), Laminaria angustata (36.6%, Phaeophyta), Ecklonia cava (35.9%, Phaeophyta) and Chondrus ocellatus (34.7%, Rhodophyta).Among the seaweed, only S. ringgoldianum and P. yezoensis were effective against both Ehrlich carcinoma and Meth A fibrosarcoma.Seaweeds contain a large quantity of each chemically characteristic mucilaginous polysac charides.These polysaccharides have recently been demonstrated to reveal some biological activities. For examples, alginate depresses plasma cholesterol level,1) carrageenan activates Hageman factor, one of the blood coagulation factors,2) a component has a cardiotonic activity,3) fucoidan inhibits blood coagulation and a blood clearance factor,4) and so on. Thus, it seems valuable to investigate marine algae from such a point of view.In the meantime, the antitumour activity of seaweed has received much attention.One of earlier works to be mentioned is that water ex tracts of seaweed showed the antitumour activity.5) Ito and Sugiura6) have also obtained a polysac charide fraction with antitumour activity from Sargassum thunbergii.The fraction showed a great ILS value (Increase in Life Span) against Ehrlich carcinoma (ascite form). Water extract from Sargassum kjellmanianum showed in the same way a higher antitumour activity against Sarcoma 180.7) The entities of these activities were assumed to be related to polysaccharides8) such as in the case of mushroom.9) Generally, no quick and drastic effects were expected to such kinds of natural products as mentioned above in constrast with chemothera pentic drugs. We, therefore, suspected that these seaweed products suppress tumour genesis as an immunostimulator or a vaccinelike substance to affect biological response modifiers when they were introduced into the body as a daily food.From this point of vi...