menaquinone

noun1

1. •
   A pale yellow crystalline naphthoquinone C₄₁H₅₆O₂ that is obtained especially from putrefied fish meal and produced by bacteria in the large intestine and essential for the blood-clotting process. It is much more unsaturated than vitamin K₁ and slightly less active biologically, and is an isoprenoid derivative of menadione.