Antitumor Activity of the Macromolecular Fraction from a Fijian Tunicate Didemnum varians

The high-molecular weight fraction from the aqueous exract of the tunicate Didemnum varians was found to have antitumor activity against Sarcoma 180 solid tumors in ICR mice, The assocaite toxicity with antitumor activity in the extract disappeared by the pronase E digestion. The pronase digest with molecular weight over 10,000 Da caused complete disappearance of tumor when injected into lesion, in the dose of 250 mg/kg, The inhibition ratio observed with iv injection was less than the high values achieved by local injection, but still significant. The cytocidal activity of the pronase digest was found to reduce when compared with those of the intact specimen. Lower-molecular weight fractions which were obtained by the enzyme digestion and successive ultrafiltration gave high cytocidal activity against Sarcoma 180 tumor cells in vitro, but had only weak antitumor activity in vivo. These results suggested that the main antitumor component in D. valians was high-molecular weight and the activity was mainly due to its carbohydrate portion. The aqueous extract prepared from the different lots of D. varians showed high antitumor activity but no toxicity.