An Overview of the Antimicrobial Properties of Hop

Abstract

Hop (Humulus lupulus L., Cannabaceae) is an edible and medicinal plant. Female inflorescences (hops) are used in the brewing industry for their bitterness and for their antiseptic properties. Hops are also used as traditional herbal medicinal product to help relieve the mild symptoms of mental stress and to aid sleep. The research on hop and on its secondary metabolites has accelerated considerably over the course of the past ten years, due to the ability of this plant to biosynthesize original prenylated phenolic compounds (phloroglucinol derivatives well known as bitter acids, chalcones, flavanones). Some of them have demonstrated a wide range of biological and pharmacological activities, including estrogenic, anti-inflammatory, antioxidant, cancer chemopreventive, and antimicrobial effects. This chapter is an overview of the antimicrobial potential of hops. The antibacterial properties of female inflorescences against Gram-positive bacteria have been well-documented. Xanthohumol, the main prenylated chalcone of hops, and lupulone, the leading compound of β-acids, show a very strong activity. Hops also inhibit the replication and the proliferation of some viruses such as hepatitis C virus (HCV) and human immunodeficiency virus (HIV). Antifungal activity is limited to studies on few fungal pathogens including Trichophyton sp., Mucor rouxianus, and Fusarium oxysporum. Some secondary metabolites of hops also strongly inhibit the causal pathogen of malaria, Plasmodium falciparum. The numerous highlighted antimicrobial activities in this chapter show the promising interest of hops’ phenolic compounds for pharmaceutical, cosmetic, and food industries.