Table 1.

The mechanisms of the secondary metabolites with potential antimicrobial properties.

Category	Plant-Derived Compounds	Antimicrobial Effects	Mechanism	References
Flavonoids	Aspilia mossambicensis, Ocimum gratissimum, and Toddalia asiatica extracts	Methicillin-resistant Staphylococcus aureus (MRSA) and P. aeruginosa	The interaction with membrane proteins resulted in increased cell membrane permeability and the disruption of the cell wall	[13]
Alkaloids	Berberine presented in roots and stem-bark of Berberis species	Antibacterial, antifungal, antiviral effects	Insertion of DNA to RNA polymerase, gyrase and topoisomerase IV, and nucleic acid	[17]
	The ethanol extract of Tabernaemontana catharinensis root bark	Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa	Endogenous indole that plays a role
Terpenes	Sesquiterpenes isolated from different plants	The inhibition of the growth of Gram-positive bacteria and Mycobacterium tuberculosis	Not fully understood	[17]
Quinones	2,6-dimethoxy-1,4-benzoquinone (DMBQ) extracted from wheat germ	S. aureus and Bacillus cereus	Provide free radicals to irreversibly bind to the nucleophilic amino acids in microbial protein to cause protein function loss	[18]