Influence of triterpenoids present in apple peel on inflammatory gene expression associated with inflammatory bowel disease (IBD).

Various ursanic, oleanic and lupanic pentacyclic triterpenoids found in apple peel were studied for anti-inflammatory effects in vitro using T84 colon carcinoma cells. After pretreatment with single triterpenoids, cells were stimulated with pro-inflammatory cytokines (TNF-α, INF-γ, IL-1β). Regulation of mRNA expression was analysed for three specific inflammation-associated marker genes (TNF-α, IL-8, IP-10) using qRT-PCR. Furthermore, the effects of ursolic acid (UA) and oleanolic acid (OA) on the synthesis of certain pro-inflammatory proteins were examined. IP-10 expression was inhibited in a dose-dependent manner by all the tested compounds at concentrations ≥25 μM. The mRNA expression of TNF-α was slightly affected and the IL-8 level was increased. At the protein level, UA and OA (25 μM) reduced the synthesis of IP-10; sICAM-1, IL-23 and GROα were slightly repressed. The TNF-α level was not modulated, whereas induction of IL-8 was increased. UA also enhanced the synthesis of IL-1ra, while OA suppressed the level of I-TAC. The present study confirms that triterpenoids present in apple peel and β-damascone may be implicated in the anti-inflammatory properties of apple constituents, suggesting that these substances might be helpful in the treatment of IBD as nutrient supplements.