We have already found and reported that several antitumor substances are obtained from meat portion of shellfish and exhibit wide antitumor spectra with little or no cytotoxicity (refer to Japanese Patent Publication No. 8088/82 and Japanese Patent KOKAI Nos. 41314/79 and 41315/79). To be concrete, the first substance we found is a water-soluble, thermally stable glycoprotein having a molecular weight range within the limits of 100,000 and 300,000 (Japanese Patent Publication No. 8088/82). Japanese Patent KOKAI No. 41314/79 describes four substances all of which are water-soluble glycoprotein substances having an average molecular weight of about 20,000 and an isoelectric point of pH 4.5 with somewhat different physical properties from one another and are extracted from meat portion of scallop from which the liver has been removed. Japanese Patent KOKAI No. 41315/79 provides a water-soluble glycoprotein substance having an average molecular weight of 10,000.about.30,000 which is obtained from meat portion of shellfish, particularly of scallop, wreath shell, tokobushi (Haliotis japonica) and pearl-oyster, from which the liver has been removed.
After that, we have further found that the liquid portion which comes from cooking of raw shellfish with a hot aqueous solvent or with the vapor of such solvent for taking up edible portions thereof and which is to be discarded as waste can also serve as raw material from which water-soluble, macromolecular glycoprotein substances similar to those already obtained from shellfish as above-mentioned are recovered and that these substances have a range of molecular weights within the limits of from 10,000 to 300,000 and possess a significant antitumor activity (refer to T. Sasaki et al, U.S. patent application Ser. No. 404,971, now U.S. Pat. No. 4,390,468).
Thus, the known antitumor substances derived from shellfish may be divided into two broad classes, namely water-soluble glycoproteins having a molecular weight range within the limits of 10,000 and 30,000, typically of around 20,000, and those having a molecular weight range within the limits of 100,000 and 300,000.
We have continued our investigations on antitumor substances derived from scallop, particularly from the liquid waste portion coming from cooking of raw scallop and now found the presence in the dry powder recovered from said waste liquid of new antitumor substance having much higher average molecular weight than those of all the known antitumor glycoprotein substances derived from shellfish. On the basis of this discovery, we have followed up our study thereon and successfully isolated a new antitumor glycoprotein substance and determined physico-chemical properties and antitumor activities thereof.