Grape seeds – a waste product as source for antibacterial agents

Grape seeds, accumulating in huge quantities after wine production, possess health beneficial effects and are therefore often taken as nutrition additives. Nevertheless, only a limited number of publications deal with the aspect of antibacterial activity of grape seed extracts.

Therefore focus of this investigation was put on the extraction and separation of the grape seed extract beside the determination of its antibacterial activity towards ten Gram-positive and Gram-negative bacterial strains, namely towards Staphylococcus aureus, Pseudomonas aeruginosa, Pneumococcus, Streptococcus pyogenes, Klebsiella, Escherichia coli, Haemophilus influenzae, Staphylococcus epidermidis, Enterococcus faecalis (VRE) and Enterococcus casilliflavus (VRE). It was found, that especially oligomers of catechin, epicatechin and their gallates – proanthocyanidins – were active towards these pathogens after fractionation of the crude grape seed extract. Additionally, due to their complex nature, a formula (1) was developed to determine the total number of possible isomers of catechin and epicatechin oligomers and polymers.

Number of theoretically possible Pn isomers=

(1)

n ... polymerization degree

m ... number of occurring 2-O7 linkages; 0 ≤ m ≤ n-1

The impact of proanthocyanidins as antibacterial agents towards ten Gram-positive and Gram-negative bacterial strains clearly could be shown in this work.