Abstract
New antitumor alkylglycerophospholipids, in which primarily the phosphocholine moiety of the platelet activating factor (PAF) molecule was modified, were synthesized from 1-alkyl-2-substituted glycerols by introducing polar head phosphoryl groups having methylene bridges of various lengths (from 2 to 14 carbons). They were tested for PAF agonistic activity and antitumor properties. In a series of 1-octadecyl-2-acetoacetylglycerophospholipids (1a-f), an increase in the length of the methylene bridge separating the phosphate and trimethylammonio group in the polar head side chain at position 3 of the glycerol backbone resulted in a progressive decrease in PAF agonistic activity and a characteristic change in antitumor activity against human promyelocytic leukemia cells (HL-60). Maximal potency was obtained with the compound having a decamethylene bridge (1e, IC50 value=1.5 μg/ml). Thus, alkylphospholipids possessing a decanmethylene bridge and a variety of substituents at position 2 (1g-n) were synthesized. They showed potent inhibitory activity with IC50 values ranging from 0.4 to 1.9 μg/ml, depending on the nature of the 2-substituent in the phospholipid molecule. In in vivo tests of the present series of alkylglycerophospholipids (1a-n), using mice bearing sarcoma 180 and mice with mammary carcinoma MM46 (both cells and compounds were given i.p.), 1-octadecyl-2-acetoacetyl-3-glyceryl ω-trimethylammoniodecyl phosphate (1e) showed the most potent life-prolonging effect. The structure-activity relationships are discussed.
