Phytochemical Profiling, Characterisation, and Antibacterial Potential of Syzygium aromaticum (Clove) Extracts Against Multidrug-Resistant Bacterial Strains

Syzygium aromaticum (clove) is well recognised for its diverse biological activities, including antimicrobial, antioxidant, and anti-inflammatory properties. The present study aimed to evaluate the antibacterial activity of clove bud extracts prepared by maceration with solvents of varying polarity n-hexane (non-polar), acetone (semi-polar), and ethanol (polar) against clinically relevant multidrug-resistant (MDR) bacterial strains. An initial qualitative phytochemical screening confirmed the presence of alkaloids, flavonoids, tannins, phenolic compounds, and terpenoids in the extracts. Antibacterial activity was determined by agar well diffusion against four organisms: Staphylococcus aureus (Gram-positive), Bacillus subtilis (Gram-positive), Escherichia coli (Gram-negative), and Pseudomonas aeruginosa (Gram-negative, MDR). The n-hexane extract exhibited the highest zone of inhibition for all organisms tested (up to 18 mm against S. aureus), followed by the acetone and ethanol extracts, indicating that the principal antibacterial constituents of clove are lipophilic in nature. GC-MS analysis of the most active n-hexane extract identified five major terpenoid constituents: β-caryophyllene (32.5%), α-humulene (12.3%), caryophyllene oxide (7.8%), α-copaene (5.6%), and δ-cadinene (4.2%). These terpenoids are known to disrupt bacterial cell membranes and inhibit microbial growth synergistically. Together, the results demonstrate that lipophilic clove extracts particularly the n-hexane fraction possess significant antibacterial activity against MDR organisms and represent a promising natural source for the development of alternative antimicrobial agents.