“…Biochemically they contain a pentaenyl group (Bruce et al, 1982;Gupta et al, 1983Gupta et al, , 1984Hirai et al, 1985) and are produced by anaerobic Bacteroides spp. (Knudsen, 1986;Lederman et al, 1980;Van Tassel et al, 1982) from precursors known as plasmalopentaenes.…”