Human beings are constantly exposed to microorganisms attacks, hence the development of a complex immune system. The first line of defense: innate immunity maintains protection, mainly by polymorphonuclear neutrophils (PMNs) being the first to react. However, sometimes these cells’ responses are exaggerated or inappropriate, requiring their modulation. Indeed, throughout history, societies have utilized medicinal plants for their healing abilities and nowadays researchers have also marked a profound interest in the immunomodulatory effects of medicinal plants such as Zingiber Officinale (Z. officinale).

In order to deepen our understanding of the biological properties of Z. officinale, we were specifically interested in studying the in vitro antioxidant and immunomodulatory effects of its aqueous extract (ZOAE) on PMNs.

The phytochemical composition of ZOAE was firstly investigated using colorimetric assays, and then its antioxidant effects were examined in vitro using a DPPH^• radical scavenging assay, nitric oxide radical inhibition, and the total antioxidant capacity method. As for the immunomodulatory effect of ZOAE, the measurement of human PMNs degranulation was carried out, monitoring the release of lysozyme, subsequent to an extract treatment of isolated PMNs, with increasing concentrations of 250, 500, and 1500 µg/mL followed by fMLP (N formyl-methionyl-leucyl-phenylalanine) stimulation (10^-6 M).

The phytochemical screening of ZOAE revealed the presence of different components. Nitric oxide radical inhibition did not show any significant activity, whereas this extract showed antioxidant activities by scavenging both DPPH^• radical and phosphomolybdate, and inhibited PMNs degranulation significantly. in a dose-dependent manner, starting with an inhibition of lysozyme release of 28.6% and reaching 63.61%, suggesting the immunomodulatory effect of ZOAE on PMNs.

Our study showed that ZOAE has both an in vitro antioxidant activity and an immunomodulatory effect on human PMNs. Further investigations are required to develop our knowledge on ZOAE, concerning its in vivo immunomodulatory effects on human PMN and the signaling pathways involved in these effects.