Table 2.

Phenolic acids explored in the context of inflammatory bowel diseases (IBDs)

Subgroups	Compounds	Dietary/Exogenous sources	Mechanisms of action (Preclinical models)	Studies in humans (including observational and intervention studies	References
Hydroxybenzoic	Gallic acid	Grapes, blackberries, strawberries, and raspberries	Downregulates the NLPR3 inflammasome and improves colitis in DSS-induced mice by reducing ammonia levels and gut microbiota dysbiosis, increasing beneficial bacteria like Lactobacillaceae and Prevotellacea. It modulates metabolic pathways, enhancing carbohydrate and bile acid metabolism while decreasing amino acid metabolism, and reduces pro-inflammatory cytokines while increasing anti-inflammatory cytokines	-	341-347
	Ellagic acid	Fruits, nuts, and seeds, such as pomegranates, raspberries, strawberries, walnuts, and almonds	Inhibits NF-κB and ERK1/2 in Caco-2 cells, reducing inflammation, oxidative stress, and intestinal permeability. Dietary EA supplementation bolsters Nrf2 pathways, protecting against oxidative stress and maintaining gut barrier integrity and morphology in piglets and TNBS-induced colitis mice. Also, reduces inflammation and histological scores in the acute and chronic DSS-induced UC models by downregulating COX-2, iNOS, and blocking p38, MAPK, NF-κB, and STAT3	-	348-353
	Protocatechuic acid	Olives, roselle, du-zhong, calamondin, and white wine grapes	One study demonstrated that PCA reduced disease activity, inflammation, and histological damage in UC mice by modulating Bacteroidetes and downregulating ferroptosis, with similar effects in Erastin-treated Caco-2 cells. Also, it reduced IL-1β, IL-6, and TNF-α levels, and improved tight junction protein distribution in DSS-induced colitis	-	356-360
	Vanillic acid	Herbs, rice, maize, and edible plants and fruits	It is demonstrated that VA treats DSS-induced mice colitis by inhibiting ferroptosis and restoring intestinal epithelium homeostasis through a CAIX-INSIG2-STIM1-SCAP-SREBP1-SCD1 pathway, preserving barrier integrity and reducing inflammation. In another study, it is found that VA alleviated colitis symptoms, reduced COX-2 expression, NF-κB p65 activation, and plasma IL-6 levels	-	361,362
Hydroxycinnamic	Caffeic acid	Plant-based foods, including fruits and vegetables, and drinks like tea or wine	Act as an anti-inflammatory modulator by suppressing NO. IL-1β, IL-6, IL-8, and TNF-α in RAAW 264.7 and HT-29 cells. It attenuates DSS-induced murine UC by interfering with macrophage activation and increasing Akkermansia populations	-	364-371
	Chlorogenic acid	Apples, artichoke, betel, burdock, carrots, eggplants, grapes, kiwi, potatoes, tea or tomatoes, among others	Alleviates DSS-induced colonic damage by reducing inflammation, oxidative stress, and apoptosis while modulating ERK1/2. P38, and JNK pathways. It downregulates miR-155 and inactivates the NF-κB/NLRP3 pathway in macrophages, offering protective effects against colitis	-	373-379
	Ferulic acid	Orange, apples, and tomatoes	It demonstrates effects on intestinal tight junctions, suppressing ER stress, NO generation, and inflammation in vitro. In vivo, it alleviates colitis in various animal models by inhibiting inflammatory pathways, and reducing cytokine levels	-	380-385
	Sinapic acid	Berries, citric fruits, oil seeds, wheat, rice, spices, and plants like Salvia officinalis and Myristica fragans	It mitigates intestinal permeability, reduces inflammatory cytokine expression, and restores tight junction protein localization both in vitro and in vivo. It inhibits the NF-κB and MAPK/ATF-2 pathways by binding to TAK1, improves gut microbiota imbalance, and reduces IBD symptoms, showing potential as a nutraceutical and pharmaceutical agent for IBD treatments	-	386-392
	Rosmarinic acid	Rosemary, basil, and mint, among others	Demonstrates significant antioxidant, anti-inflammatory, and antimicrobial properties, proving effective in alleviating intestinal inflammation, ut dysbiosis, and tight junction damage in IBD	-	393-397
	Coumaric acid	Apples, pears, grapes, oranges, tomatoes, berries, beans, potatoes, onions, maize, oats, wheat, mushrooms and medicinal herbs	-	-	399,401
	Quinic acid	Yerba mate, white, green teas, coffee, microalgae, and cyanobacteria	One study demonstrated the therapeutic potential for UC by significantly increasing HO-1, Nrf2, and NQO1 mRNA expression while reducing TNF-α and IL-1β protein levels in colon tissue. Also attenuates UC by inhibiting the TLR4-NF-κB and NF-κB-iNOS-No signaling pathway, reducing oxidative stress, inflammation, apoptosis, and histopathological damage	-	400,402