Chemical Profiling, Antioxidant, and Antibacterial Activities of Ethanolic Extract of Melaleuca cajuputi Flower and Its Mode of Action
DOI:
https://doi.org/10.48048/tis.2026.13457Keywords:
Melaleuca cajuputi, Antioxidant activity, Antibacterial activity, Liquid chromatography/mass spectrometry (LC/MS), Methicillin-resistant Staphylococcus aureus (MRSA)Abstract
Despite well-documented antimicrobial properties of Melaleuca cajuputi extracts, particularly from leaves and essential oils, the antibacterial potential of flower extracts against multidrug-resistant (MDR) pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA), remains largely underexplored. This study characterized the phytochemical composition, antioxidant, and antibacterial activities of ethanol extracts from M. cajuputi flowers. Dried flowers of M. cajuputi were extracted with ethanol, followed by phytochemical analysis using liquid chromatography/mass spectrometry (LC/MS). Antioxidant activity was determined using 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging assay. Antibacterial activity of the crude extract was assessed using the agar well diffusion method. The minimal inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined by microdilution, including time-kill assays. Scanning electron microscopy (SEM) was employed to investigate the effects of the extract on the morphology of MRSA cells. Phytochemical profiling established that the extract was abundant in phenolics, flavonoids, and tannins. Notable antioxidant capacity was observed, with IC50 values of 11.28 ± 0.30 μg/mL (DPPH) and 61.90 ± 14.84 μg/mL (ABTS). Evaluation against 5 significant bacterial pathogens, including MRSA, revealed broad-spectrum inhibitory effects. The lowest recorded MIC and MBC values were 0.33 and 5.31 mg/mL, respectively, with ranges spanning 0.33 - 125 mg/mL (MIC) and 5.31 - 250 mg/mL (MBC). Time-kill studies indicated concentration- and time-dependent bactericidal mode of action against most strains. At the same time, MRSA was primarily inhibited in a bacteriostatic manner. SEM revealed dose-dependent morphological damage to MRSA cells, including membrane disruption and shrinkage, indicating compromised cell envelope integrity. These findings indicate that M. cajuputi flower extract is a promising candidate for natural antibacterial and antioxidant applications, meriting further investigation for its role in controlling MDR bacterial infections.
HIGHLIGHTS
- Ethanolic extract of cajuputi flowers contains high phenolics, flavonoids, and tannins.
- The extract shows strong antioxidant and broad‑spectrum antibacterial activities.
- cajuputi flower extract inhibits both Gram‑positive and Gram‑negative bacteria.
- The extract acts via bactericidal and bacteriostatic modes of action.
- The extract damages MRSA cell morphology and membrane integrity.
GRAPHICAL ABSTRACT
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