In: Grape Seeds ISBN: 978-1-63484-578-6 Editors: J. M. Lorenzo Rodríguez and D. F. Ruiz © 2016 Nova Science Publishers, Inc. Chapter 10 ANTIMICROBIAL AND ANTIVIRAL ACTIVITIES OF GRAPE SEED EXTRACTS G. Pasqua 1, and G. Simonetti 2 1 Department of Environmental Biology, Sapienza Università di Roma, Rome, Italy 2 Department of Public Health and Infectious Diseases, Sapienza Università di Roma, Rome, Italy ABSTRACT Grape seed extract (GSE) is a rich source of polyphenols. The polyphenols are important secondary metabolites which play multiple essential roles in plant physiology and which show a broad range of bioactive properties in human organism, mainly as antioxidant, anti-inflammatory, anticancer, cardioprotection, and 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  Corresponding Author address: Gabriella Pasqua, Department of Environmental Biology, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185, Rome, Italy. Email: gabriella.pasqua@uniroma1.it. No part of this digital document may be reproduced, stored in a retrieval system or transmitted commercially in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.