Antimicrobial and antiviral activities of grape seed extracts

Grape seed extract (GSE) is a rich source of polyphenols, important secondary metabolites which play multiple essential roles in plant physiology and show a broad range of bioactive properties in human organism, mainly as antioxidant, anti-inflammatory, anticancer, cardioprotection, antiaging. GSE is recognized as a complex mixture of monomeric, oligomeric, and polymeric flavan-3-ols. The principal monomers identified are (+)-catechin, (−)-epicatechin, (−)-epicatechin gallate, (−)-epigallocatechin, and (−)-epigallocatechin gallate. The content of flavan-3-ols in seed grapes is influenced by several factors mainly cultivar, irrigation, nitrogen fertilization, delayed harvest, and storage conditions. Antimicrobial and antiviral activities of GSE have been described. Moreover, some researchers showed that seed extracts were more effectively antimicrobial than other parts of grapes. The decrease order of the antimicrobial activity is seed, skin and flesh grape extracts. We demonstrated, for the first time, a significant correlation between the content of the flavan-3-ols in GSEs, with a polymerization degree ≥4, and antifungal activity. Recently, we also demonstrated a significant inhibition of Candida albicans, in an experimental murine model of vaginal candidiasis, using GSE with high content of polymeric flavan-3-ols. Technologies to deliver GSEs for an effective inhibition of pathogens have been reported. GSE is Generally Recognized as Safe (GRAS), approved by Food and Drug Administration (FDA) and also sold as dietary supplement. Antimicrobial activity together with lack of toxicity suggests that GSE could be used for the prevention and control of infection diseases without side effects, making greater potential for grape in the field of food and pharmaceutical application.