Here are the matches of the constituents of seminal fluid with their respective functions:
Mucin
Function: Neutralization of acidity in male urethra
Prostaglandins
Function: Cervical dilation and uterine contraction
PSA (Prostate-Specific Antigen)
Function: Seminal liquefication
Seminalplasmin
Function: Antibiotic
These matches correctly associate each constituent with its primary role in seminal fluid.