Phytochemical characterization and immunomodulatory effects of aqueous, ethanolic extracts and essential oil of Syzygium aromaticum L. on human neutrophils

In Morocco, the flower buds of Syzygium aromaticum L (Clove) from Myrtaceae are essential in traditional medicine; they are used in many forms (infusion, maceration, and essential oil) and are suggested to mitigate inflammatory conditions such as muscle and dental pain as well as rheumatic diseases. This study aims to chemically characterize the aqueous and ethanolic extracts as well as the essential oil from cloves; also, we aimed to evaluate their effects on the bactericidal activity of human neutrophils compared with eugenol. The chemical composition of extracts was evaluated via qualitative phytochemical screening followed by quantitative screening using spectrophotometry and HPLC technique. The essential oil was analyzed by the GC-MS technique. The PMNs bactericidal activity of extracts, essential oil, and eugenol was carried out by MTT assay. The screening of extracts showed the presence of phenols, flavonoids, flavones aglycones, coumarins, and tannins. HPLC analysis revealed the presence of numerous phenolic compounds such as gallic acid, rutin, and quercetin while the GC-MS analysis of essential oil showed that the main components are eugenol (78.67%), eugenyl acetate (11.77%), and caryophyllene (6.85%). The aqueous, ethanolic extracts and essential oil showed an immunomodulatory activity by exerting a significant inhibition of neutrophil bactericidal activity in a dose dependent-manner reaching maximal inhibition at the concentration of 200 µg/ml with only 29.92%, 32.24%, and 48.15%, respectively (p < 0.001).Our study showed the immunomodulatory virtues of cloves as a natural anti-inflammatory agent. The strength of this effect is related to the presence of eugenol and the extraction forms used