Other names: Piper nigrum
In Vitro study: Extracts from black pepper leaf inhibit 5alpha-reductase (5AR)
https://www.ncbi.nlm.nih.gov/pubmed/18057734
Mouse study: Black pepper extract has ambiguous sexual effects
http://www.scialert.net/abstract/?doi=rjmp.2015.42.47
Mouse study: Black pepper extract considerably raises testosterone, and sperm count, but only slight boost to sperm motility
http://pubs.sciepub.com/ajmbr/4/1/1/
Subjects: 27 male Swiss albino mice, divided into 3 groups.
Groups: Control, black pepper water extract, black pepper alcohol extract
Delivery method: Black pepper extracts put into edible mouse pellets.
Found: More serum testosterone, more sperm, but not more sperm motility (that latter is apparently a DHT dependent process - see testosterone-vs-dht).