The secretions from the seminal vesicles make up the bulk of the volume of the seminal fluid and contain fructose, prostaglandins, citric acid, inorganic phosphorus, potassium, and coagulant proteins. Of these, fructose is a highly useful bio-marker indicating seminal vesicle function, and also serves as an energy substrate for the spermatozoa.
This a qualitative test based on the estimation of colour change after incubation of the semen sample with Seliwanoff reagent. Very small amount of semen (0.5ml) is mixed with the reagent (4.5ml) and boiled for 10-15 minutes. Change in colour from colourless to deep brick red indicates presence of Fructose.