Antimicrobial and Antibiofilm Effects of Aquilaria Malaccensis Ethanolic Leaves Extract Against Multidrug-Resistant Pathogens

Goh, Xue Qi (2026) Antimicrobial and Antibiofilm Effects of Aquilaria Malaccensis Ethanolic Leaves Extract Against Multidrug-Resistant Pathogens. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

The global threats of multi-drug resistant (MDR) pathogens underline the urgent need to explore natural alternatives as antimicrobial agents. Aquilaria malaccensis leaves extract has been reported to possess various phytochemicals with antibacterial properties, highlighting its potential to be developed into a natural antibiotic. This study aims to evaluate the antimicrobial and antibiofilm activities of Aquilaria malaccensis ethanolic leaves extract (AMEL) against MDR bacteria (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa). The minimum inhibitory concentration (MIC) of AMEL was determined by broth microdilution assay. The growth kinetics of the selected bacterium under different treatment conditions were also observed for 24 hours. The biofilm inhibition and eradication effects were studied using crystal violet assay to assess the antibiofilm properties of AMEL. Molecular docking using MzDOCK was performed to predict the interactions between the five most abundant phytochemicals identified in AMEL (3’-O-methyltaxifolin, eriodictyol, carthamidin, 2,3-dihydroirigenin, and gardenin) and key biofilm-associated proteins of K. pneumoniae (mrkH, luxS, and fimH). Results showed that AMEL completely inhibited K. pneumoniae at 5 mg/mL, while no inhibition detected against other bacteria, even at the highest concentration tested (8 mg/mL). A concentration-dependent suppression of K. pneumoniae proliferation was observed from the growth curve. Bacterial growth was remarkably slowed when tested at sub-inhibitory concentration (0.5×MIC) and completely suppressed at inhibitory concentration (1×MIC) compared to the growth control which demonstrated robust proliferation. Interestingly, 5 mg/mL of AMEL exhibited more than 90% inhibitory effects in biofilm formation as well as eradication of established biofilms. Eriodictyol demonstrated strongest binding affinity against the three biofilm-related proteins via molecular docking, suggesting its potential role in disrupting bacterial biofilm regulation pathways, quorum sensing, and adhesion. Overall, these findings proved that AMEL is a promising antimicrobial agent, with eriodictyol as the lead compound.