The Role of Plant-Derived Natural Products in the Management of Inflammatory Bowel Disease-What Is the Clinical Evidence So Far?

Abstract

Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are a major healthcare challenge worldwide. Disturbances in the immune system and gut microbiota followed by environmental triggers are thought to be part of the aetiological factors. Current treatment for IBD includes corticosteroids, immunosuppressants, and other biologic agents; however, some patients are still unresponsive, and these are also linked to high financial load and severe side effects. Plant-derived natural products are rich in phytochemicals and have been used as healing agents in several diseases since antiquity due to their antioxidant, anti-inflammatory, and immunomodulatory properties, as well as gut microbiota modulation. Numerous in vitro and in vivo studies have shown that phytochemicals act in key pathways that are associated with the pathogenesis of IBD. It is also reported that the use of plant-derived natural products as complementary treatments is increasing amongst patients with IBD to avoid the side effects accompanying standard medical treatment. This review summarises the relevant evidence around the use of plant-derived natural products in the management of IBD, with specific focus on the clinical evidence so far for Curcumin, Mastiha, Boswellia serrata, and Artemisia absinthium.

Keywords: Artemisia absinthium; Boswellia serrata; Curcumin; Mastiha; gut microbiota; inflammatory bowel disease; phytochemicals.

Figure 1

Effects of plant-derived natural compounds on IBD. AOPP = advanced oxidation protein products, IgA = immunoglobulin A, LOP = lipid-oxidised products, NF-kB = nuclear factor kappa B, MAPK = mitogen-activated protein kinase, MPO = myeloperoxidase, PPAR-γ = peroxisome proliferator-activated receptor, ROS = reactive oxygen species, RNS = reactive nitrogen species, TNF-a = tumour necrosis factor alpha, TLR = Toll-like receptors, Nrf-2 = nuclear factor erythroid 2–related factor 2.

Figure 2

Main bioactive compounds of (a) Curcuma longa (curcumin [38]); (b) Mastiha (α-pinene [39], β-pinene [40], β-myrcene [41], mastihadienonic acid [42], isomastihadienonic acid [43]); (c) Boswellia serrata (boswellic acid [44]); (d) Artemisia absinthium (α-thujone [45], camphene [46], absinthin [47]). Source of chemical structures: PubChem [48].