title: Inhibition of metalloproteinase and proteasome activities in colon cancer cells by citrus peel extracts.
abstract: BACKGROUND
  Citrus peels are consumed in the form of infusions, candy or wine, based on their well-documented nutritional and medicinal properties. This study sought to investigate the effect of some citrus peels' [grapefruit (Citrus paradisii), orange (Citrus sinensis) and shaddock (Citrus maxima)] extracts on matrix metalloproteinase (MMP) and proteasome activities in primary human colonic tumor (Caco-2) and the metastatic cell lines (LoVo and LoVo/ADR) in a bid to explain the possible mechanism by which the peels could manage/prevent colon cancer.
  
  
  METHODS
  The inhibition of MMP and proteasome activities in the cells by the peel extracts, as well as the identification of phenolic compounds using high-performance liquid chromatography with diode-array detection (HPLC-DAD), was determined.
  
  
  RESULTS
  Orange peel extracts had the strongest inhibition of MMP in Caco-2 and LoVo cells, while shaddock had the least. Shaddock peel extracts also had the least MMP inhibition in LoVo/ADR lysates. Grapefruit had the least proteasome inhibition in Caco-2 and LoVo lysates, while there was no significant (p>0.05) difference in the proteasome inhibition of the peel extracts in LoVo/ADR lysates. The extracts inhibited proteasome activity in extract-treated cells, and HPLC fingerprinting of the extracts revealed the presence of some phenolic compounds such as quercetin, caffeic acid, kaempferol, catechin and naringin.
  
  
  CONCLUSIONS
  The inhibition of MMP and proteasome activities in colon cancer cell lines suggests the potential use of citrus peels as functional food in the management and/or prevention of colon cancer.
authors.forename: Ayokunle O
authors.initials: AO
authors.lastname: Ademosun
authors.forename: Ganiyu
authors.initials: G
authors.lastname: Oboh
authors.forename: Sabina
authors.initials: S
authors.lastname: Passamonti
authors.forename: Federica
authors.initials: F
authors.lastname: Tramer
authors.forename: Lovro
authors.initials: L
authors.lastname: Ziberna
authors.forename: Aline Augusti
authors.initials: AA
authors.lastname: Boligon
authors.forename: Margareth Linde
authors.initials: ML
authors.lastname: Athayde
mesh_terms: D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D002957:Citrus / Q000737:chemistry*; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D005638:Fruit / Q000737:chemistry*; D006801:Humans; D045726:Metalloproteases / Q000037:antagonists & inhibitors*; D010636:Phenols / Q000737:chemistry / Q000494:pharmacology; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects*
chemical_list: D010636:Phenols; D010936:Plant Extracts; D045726:Metalloproteases; D046988:Proteasome Endopeptidase Complex