Bactericidal and cytotoxic activity of a diarylheptanoid (etlingerin) isolated from a ginger (Etlingera pubescens) endemic to Borneo

• Published in: Journal of applied microbiology Vol. 127; no. 1; pp. 59 - 67
• Main Authors: Daniel‐Jambun, D., Ong, K.S., Lim, Y.Y., Tan, J.B.L., Yap, S.W., Lee, S.M.
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01-07-2019
• Subjects: Acetic acid; Animal models; Animals; Anti-Bacterial Agents - adverse effects; Anti-Bacterial Agents - isolation & purification; Anti-Bacterial Agents - pharmacology; Anti-Bacterial Agents - toxicity; antimicrobial; Antimicrobial activity; Antimicrobial agents; biocides; Borneo; Cell Death - drug effects; Cell Line, Tumor; Cell lines; Cells, Cultured; Curcumin; Curcumin - pharmacology; Cytotoxicity; Diarylheptanoids - adverse effects; Diarylheptanoids - isolation & purification; Diarylheptanoids - pharmacology; Diarylheptanoids - toxicity; Etlingera; Ginger; Gram-Positive Bacteria - drug effects; Humans; Identification methods; mechanism of action; Membrane permeability; Microbial Sensitivity Tests; Minimum inhibitory concentration; natural product; Organic chemistry; Permeability - drug effects; phenolic; Plant Extracts - chemistry; Plant Extracts - pharmacology; Toxicity; Zingiber officinale - chemistry; Zingiberaceae; Borneo; antimicrobial; ginger; natural product; mechanism of action; biocides; cytotoxicity; Zingiberaceae; phenolic
• DOI: 10.1111/jam.14287
• EISSN: 1365-2672
• ISSN: 1364-5072

Aims
The aim of this study was to investigate the antimicrobial activities of Etlingera pubescens, and to isolate and identify the antimicrobial compound.
Methods and Results
The crude extracts of E. pubescens were obtained through methanol extraction, and evaluated for antimicrobial activities. From this extract, 1,7‐bis(3,4‐dihydroxyphenyl)heptan‐3‐yl acetate (etlingerin) was isolated. When compared to curcumin (a compound with a similar chemical structure), etlingerin showed twofold lower minimum inhibitory concentration values while also being bactericidal. Through time kill assay, etlingerin showed rapid killing effects (as fast as 60 min) against the Gram‐positive bacteria (Staphylococcus aureus ATCC 43300 and Bacillus subtilis ATCC 8188). Further assessment revealed that etlingerin caused leakage of intracellular materials, therefore suggesting alteration in membrane permeability as its antimicrobial mechanism. Cytotoxicity study demonstrated that etlingerin exhibited approximately 5‐ to 12‐fold higher IC50 values against several cell lines, as compared to curcumin.
Conclusions
Etlingerin isolated from E. pubescens showed better antibacterial and cytotoxic activities when compared to curcumin. Etlingerin could be safe for human use, though further cytotoxicity study using animal models is needed.
Significance and Impact of the Study
Etlingerin has a potential to be used in treating bacterial infections due to its good antimicrobial activity, while having potentially low cytotoxicity.