Preliminary GC-MS Metabolite Profiling and Antibacterial Activity against Staphylococcus Aureus of Hypogymnia tubulosa from Tlogosari, Bondowoso-Indonesia

The rise of antimicrobial resistance has driven the search for new antibacterial agents derived from natural products, including lichens, which are known to contain diverse bioactive secondary metabolites. Hypogymnia tubulosa has been traditionally recognized for its medicinal value, yet its antibacterial properties and underlying mechanisms remain understudied. This study aimed to identify the secondary metabolites present in Hypogymnia tubulosa and evaluate their potential antibacterial mechanisms based on established biochemical activities. This study aimed to perform preliminary metabolite profiling of Hypogymnia tubulosa using Gas Chromatography-Mass Spectrometry (GC-MS) analysis and evaluate its antibacterial activity against Staphylococcus aureus using a microdilution assay. The lichen H. tubulosa was collected, authenticated, dried, and extracted using methanol, followed by fractionation in n-hexane. Antibacterial activity was evaluated against S. aureus using a microdilution assay to assess growth inhibition. Chemical profiling of the extract was performed using Gas Chromatography-Mass Spectrometry (GC-MS) to identify secondary metabolites, which were interpreted based on known antibacterial mechanisms. Chemical profiling of the methanol fraction was performed using GC-MS to putatively identify secondary metabolites based on spectral library matching. The methanol fraction of H. tubulosa showed notable antibacterial activity against S. aureus, achieving approximately 72% growth inhibition, whereas the n-hexane fraction displayed no inhibitory effect. GC-MS analysis identified 22 metabolites spanning aldehydes, phenols, fatty acids, diterpenes, ketones, esters, alcohols, and alkanes. These compounds are associated with membrane disruption, metabolic interference, and enzyme inhibition, supporting the extract’s observed antibacterial effect. Several detected metabolites have previously been reported to exhibit antibacterial related bioactivities, which may contribute to the observed growth inhibition of S. aureus. Hypogymnia tubulosa contains diverse secondary metabolites with mechanisms suggesting strong antibacterial potential. The methanol fraction of H. tubulosa demonstrated preliminary antibacterial activity against S. aureus and contained diverse putatively identified metabolites detected by GC-MS analysis. The lichen shows promise as a natural source for developing antibacterial agents and warrants further biological evaluation to validate its in vitro and in vivo efficacy.