NEW CHLOROPHYLL-A-RELATED COMPOUNDS ISOLATED AS ANTIOXIDANTS FROM MARINE BIVALVES

New chlorophyll-a-related compounds chlorophyllone a [1], chlorophyllonelactone a [2], and chlorophyllonic acid a methyl ester [3] as well as pyropheophorbide a [4] were isolated as the main antioxidants from the edible parts of the short-necked clam, Ruditapes philippinarum. Our continuing studies on new antioxidants have resulted in the isolation of the analogous compounds purpurin 18 [6], purpurin 18 methyl ester [7], and 13(2)-oxopyropheophorbide a [8]. Compound 5, an epimeric isomer of 1, together with 2, 3, and 4, was isolated from the viscera of the scallop, Patinopecten yessoensis. The presence of 1, 2, and 3 in the viscera of the oyster Crassostrea sp. and 1 in the mixture of attached diatoms (Fragilaria oceanica, Fragilaria cylindus. Nitzschia closterium, Nitzschia seriata, Cocconeis pseudomarginata, and Hyalodiscus stelliger are predominant) cultured for seedling production of juvenile abalone was also confirmed by spectroscopic evidence.