Olive mill wastewater (OMW) is produced seasonally by the olive oil-producing countries. A large amount
of liquid waste results from olive oil extraction, with a very high organic load which renders it difficult to treat. Wastewater represents also a significant source of polyphenols which can be revalorized and used for medical or agro-alimentary purposes. The extraction of polyphenols will improve the wastewater biodegradation and reduce its phytotoxicity. The objective of this study was to extract polyphenols from OMW and to investigate their effect on reactive oxygen species (ROS) production by human neutrophil. Polyphenols were extracted from OMW by an established technique. Neutrophils, isolated from blood of healthy volunteers, were incubated with increased concentrations of polyphenol extract and ROS production was measured by luminol-amplified chemiluminescence and cytochrome c reduction techniques. Results show that the polyphenol extract from OMW inhibited phorbolmyristate
acetate (PMA)-stimulated neutrophil ROS production as measured by the chemiluminescence assay. The polyphenols extract from OMW also inhibited neutrophil superoxide production as measured by the cytochrome c reduction assay; as well as H2O2 production as measured by flow cytometry. Also, the polyphenol extract reacted with pure H2O2 but did not affect superoxide anions production by the xanthine/xanthine oxidase enzymatic system. Our results show that polyphenols extracted from OMW exert a strong antioxidant effect and they could have an anti-inflammatory effect by inhibiting neutrophil ROS production and by scavenging hydrogen peroxide, thus limiting their toxic effects. OMW could be used to extract polyphenols for medicinal applications.