Table 1.

Mode of actions and antibacterial target strains of functional phytochemicals.

Class		Source(s)	Compounds	Mode of action	Reported target bacteria	References
Terpenoids	Monoterpenes	Essential oils of several aromatic plants	Palmarosa oil (Cymbopogon martinii), cinnamon oil, geraniol, carvacrol, thymol, eugenol	Antimicrobial, pest control, antioxidant, anti-inflammatory, anti-fungal	Escherichia coli, Salmonella typhimurium, Streptococcus pneumoniae, S. pyogenes, Staphylococcus aureus	(41–43)
	Diterpenes	Essential oil from berries, traditional Chinese medicine (Euphorbiaceae, Lamiaceae, and Taxaceae family)	Andrographolide (Andrographis paniculata), oridonin	Antimicrobial, anti-inflammatory, anticancer, antioxidant	Mycobacterium tuberculosis	(41, 44)
	Triterpenes	Olives, olive tree leaves, and virgin olive oil	Oleanolic acid, ursolic acid, ginsenoside, gypenosides, betulinic acid, rotundic acid, amyrin, saponins, tirucallane-type of Eurycoma longifolia	Antioxidant, antimicrobial, antimalaria, anticancer, treatment of chronic diarrhea	Acinetobacter baumannii, St. aureus, Bacillus cereus, Pseudomonas aeruginosa	(9, 41, 45–47)
	Tetraterpenes	Colored fruits, green leafy vegetables, microalgae	Astaxanthin, β-carotene, fucoxanthin	Antioxidant, anti-inflammatory, treatment of cardiovascular disease, anticancer		(41, 48, 49)
	Sesquiterpenes	Odor of essential oils	α-Bisabolol, dehydrocostuslactone	Antioxidant		(41, 50)
Phenolic compounds	Polyphenols	Berries, needles of Cedrus deodara, mushroom	Anthocyanins, cyanidins, quercetin, myricetin, rutin, tannins, CHQA	Enhancing the health of the gut (impact on gut microbiome), antioxidant, anti-adhesion	E. coli, St. aureus, Neisseria gonorrhoeae, Pasteurella multocida	(18, 51, 52)
		Bran or hull	Benzoic acid, cinnamic acid, benzaldehydes	Antifungal, antimicrobial	A. bauamnnii, Candida albicans, Campylobacter jejuni, E. coli, Listeria monocytogenes, Sa. enterica,	(5, 23, 53)
		Chili peppers, oats	Capsaicinoids, avenanthramides	Pest control, antioxidant, anti-inflammatory, inhibition of LDL oxidation, thermal hyperalgesia, beneficial in obesity	Helicobacter pylori, S. pyogenes, St. aureus, St. typhimurium, P. aeruginosa	(53–56)
		Grapes, red wine, sesame, green tea, cocoa (flovanols)	Resveratrol, (–)-epigallocatechin gallate, ellagic acid, lignans, curcumin, caffeic acid, gallic acid	Anti-inflammatory, anti-colone cancer, antioxidant, Enhancing the health of the gut, antimicrobial	Sa. Typhimurium, St. aureus, H. pylori, Clostridium spp., Bacteroides spp.	(51–53, 57)