Coenzymes are low-molecular organic compounds of a non-protein nature that serve as a transfer link between the substrate and the enzyme in biochemical reactions. The word “coenzyme” comes from the Latin word сferre (to carry away) and the Greek words “(superstructure-base)”.
For example: biotin, flavin, iron porphyrin, lipoic acid, menadione (Vitamin K), pyridoxal phosphate (Vitamin B6), thiamine phosphate, citrate, adenosine diphosphate, etc. We can call most of them vitamins and this is not accidental, because in essence they really are; they are coenzymes of the Krebs cycle, tricarboxylic acid cycle, Bethe-Spuryu cycle and other processes of acetylCoA binding with their carriers in biological membranes.