Alkylglycerols (alkyl-Gro) are ether lipids abundant in the liver of some elasmobranch fish species such as ratfishes and some sharks. Shark liver oil from Centrophorus squamosus (SLO), or alkyl-Gro mix from this source, have several in vivo biological activities including stimulation of hematopoiesis and immunological defences, sperm quality improvement, or anti-tumor and anti-metastasis activities. Several mechanisms are suggested for these multiple activities, resulting from incorporation of alkyl-Gro into membrane phospholipids, and lipid signaling interactions. Natural alkyl-Gro mix from SLO contains several alkyl-Gro, varying by chain length and unsaturation. Six prominent constituents of natural alkyl-Gro mix, namely 12:0, 14:0, 16:0, 18:0, 16:1 n-7, and 18:1 n-9 alkyl-Gro, were synthesized and tested for anti-tumor and anti-metastatic activities on a model of grafted tumor in mice (3LL cells). 16:1 and 18:1 alkyl-Gro showed strong activity in reducing lung metastasis number, while saturated alkyl- Gro had weaker (16:0) or no (12:0, 14:0, 18:0) effect. Multiple compounds and mechanisms are probably involved in the multiple activities of natural alkyl-Gro.

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Oral alkylglycerols (AKG) from shark liver oil (SLO) have multiple biological activities including immuno-stimulation and anti-tumour properties. In several cell types they are incorporated into phospholipids and therefore they may produce modified messengers and mediators following cellular activation of the phospholipase pathway. Structure of naturally occurring AKG vary depending on length and unsaturation of the alkyl chain. We synthesized six of the major natural constituants of AKG from SLO and tested their anti-tumour and anti-metastasis activities on a model of solid tumour grafted in mice. We found that unsaturated compounds were the most active for reducing tumour volume, lung metastasis number, and splenomegaly. Saturated compounds had weaker, no, or deleterious activities on this model. These data suggest that the selective use of unsaturated natural AKG would improve anti-tumour activities as compared to natural mix of AKG.