Comparison of Chemical Composition and Bioactivities of Essential Oils from Fresh and Dry Rhizomes of <i>Zingiber zerumbet</i> (L.) Smith

Abstract

The chemical constituents and the antioxidant, antimicrobial, and cytotoxic activities of fresh rhizome essential oil (FR-EO) and dry rhizome essential oil (DR-EO) of <i>Zingiber zerumbet</i> (L.) Smith obtained from Southwest China were compared. Zerumbone was the predominant component in both FR-EO and DR-EO (75.0% and 41.9%, respectively). FR-EO, DR-EO, and zerumbone were all demonstrated to have significant antimicrobial capacity against <i>Staphylococcus aureus</i>, <i>Bacillus subtilis</i>, <i>Escherichia coli</i>, and <i>Proteus vulgaris</i>, with minimum inhibitory concentration (MIC) ranging from 31.25 to 156.25 <i>μ</i>g/mL and minimum bactericidal concentration (MBC) ranging from 62.50 to 625.00 <i>μ</i>g/mL. Zerumbone showed the strongest antimicrobial potential against all tested microorganisms compared with the fresh and dry rhizome essential oils. FR-EO was found to be more active than DR-EO against <i>Staphylococcus aureus</i>, <i>Bacillus subtilis</i>, <i>Escherichia coli</i>, and <i>Proteus vulgaris</i>. FR-EO, DR-EO, and zerumbone all showed significant cytotoxic activity against K562, PC-3, and A549 human tumor cell lines in a time- and concentration-dependent manner. Zerumbone exhibited the strongest antiproliferative activity against all tested human tumor cell lines with an IC₅₀ of 4.21-11.09 <i>μ</i>g/mL for 72 h incubation, as compared with the fresh and dry rhizome oils. The cytotoxic activity of FR-EO (IC₅₀: 10.48-14.51 <i>μ</i>g/mL for 72 h) was found to be significantly higher (<i>p</i> < 0.05) than that of DR-EO (IC₅₀: 13.83-33.24 <i>μ</i>g/mL for 72 h). FR-EO, DR-EO, and zerumbone exhibited selective cytotoxic activity to tumor cells, with a significantly low cytotoxicity to normal cells (MRC-5, IC₅₀: 56.98-147.29 <i>μ</i>g/mL). However, FR-EO, DR-EO, and zerumbone all exhibited weak free-radical-scavenging activity according to DPPH and ABTS analysis. The findings highlighted in this study show that FR-EO provides appreciably higher content of the bioactive compound, zerumbone, and has higher antimicrobial and cytotoxic properties than DR-EO. Thus, fresh <i>Z. zerumbet</i> rhizome should be preferred in cosmetic, food, and pharmaceutical applications.