Abstract
BackgroundZingiber zerumbet rhizome and its bioactive metabolites have previously been reported to exhibit innumerable pharmacological properties particularly anti-inflammatory activities. In the present study, the 80% ethanol extract, essential oil and zerumbone of Z. zerumbet rhizomes were explored for their in vitro immunosuppressive properties on chemotaxis, CD11b/CD18 expression, phagocytosis and chemiluminescence of isolated human polymorphonuclear neutrophils (PMNs).MethodsThe extract was analyzed quantitatively by performing a validated reversed phase high performance liquid chromatography (RP-HPLC). Zerumbone was isolated by chromatographic technique while the essential oil was acquired through hydro-distillation of the rhizomes and further analyzed by gas chromatography (GC) and GC-MS. Chemotaxis assay was assessed by using a 24-well cell migration assay kit, while CD18 integrin expression and phagocytic engulfment were measured using flow cytometry. The reactive oxygen species (ROS) production was evaluated by applying lucigenin- and luminol-enhanced chemiluminescence assays.ResultsZerumbone was found to be the most abundant compound in the extract (242.73 mg/g) and the oil (58.44%). Among the samples tested, the oil revealed the highest inhibition on cell migration with an IC50 value of 3.24 μg/mL. The extract, oil and zerumbone showed moderate inhibition of CD18 integrin expression in a dose-dependent trend. Z. zerumbet extract showed the highest inhibitory effect on phagocytic engulfment with percentage of phagocytizing cells of 55.43% for PMN. Zerumbone exhibited strong inhibitory activity on oxidative burst of zymosan- and PMA-stimulated neutrophils. Zerumbone remarkably inhibited extracellular ROS production in PMNs with an IC50 value of 17.36 μM which was comparable to that of aspirin.ConclusionThe strong inhibition on the phagocytosis of neutrophils by Z. zerumbet extract and its essential oil might be due the presence of its chemical components particularly zerumbone which was capable of impeding phagocytosis at different stages.
Highlights
Zingiber zerumbet rhizome and its bioactive metabolites have previously been reported to exhibit innumerable pharmacological properties anti-inflammatory activities
Quantification of chemical marker using reversed phase high performance liquid chromatography (RP-high performance liquid chromatography (HPLC)) According to our earlier report, the chromatograms obtained from the reversed-phase HPLC column of the 80% ethanol extract of Z. zerumbet revealed several peaks with zerumbone as the major peak, at retention time of 9.745 min (Additional file 3: Fig. S3) [9]
The reproducibility of the HPLC result was demonstrated by good precision from the method employed conforming to the %relative standard deviation (RSD) values obtained as illustrated by the small values of standard deviation for retention time and responses of the marker compounds for both intraday and interday assay precisions
Summary
Zingiber zerumbet rhizome and its bioactive metabolites have previously been reported to exhibit innumerable pharmacological properties anti-inflammatory activities. The immune system is a sophisticated network of subsystems involving the coordination of various cells, proteins and chemical signals against infectious diseases. This preeminent system is classified into innate immunity (nonspecific) and adaptive immunity (acquired or specific). Professional phagocytes like neutrophils, macrophages and monocytes are the main line of defense which perform various functions in an inflammation or immune responses. These functions include interacting, identifying, capturing foreign particles and eliminating pathogens which invades the body. Upon the invasion of pathogenic micro-organisms, foreign particles and events in the human body, the initial response in the first few hours plays a significant and critical role which is responsible for the consequence of the infection [2]
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