title: Bioassay-guided identification of an anti-inflammatory prenylated acylphloroglucinol from Melicope ptelefolia and molecular insights into its interaction with 5-lipoxygenase.
abstract: A bioassay-guided investigation of Melicope ptelefolia Champ ex Benth (Rutaceae) resulted in the identification of an acyphloroglucinol, 2,4,6-trihydroxy-3-geranylacetophenone or tHGA, as the active principle inhibiting soybean 15-LOX. The anti-inflammatory action was also demonstrated on human leukocytes, where the compound showed prominent inhibitory activity against human PBML 5-LOX, with an IC(50) value of 0.42 μM, very close to the effect produced by the commonly used standard, NDGA. The compound concentration-dependently inhibited 5-LOX product synthesis, specifically inhibiting cysteinyl leukotriene LTC(4) with an IC(50) value of 1.80 μM, and showed no cell toxicity effects. The anti-inflammatory action does not seem to proceed via redox or metal chelating mechanism since the compound tested negative for these bioactivities. Further tests on cyclooxygenases indicated that the compound acts via a dual LOX/COX inhibitory mechanism, with greater selectivity for 5-LOX and COX-2 (IC(50) value of 0.40 μM). The molecular features that govern the 5-LOX inhibitory activity was thus explored using in silico docking experiments. The residues Ile 553 and Hie 252 were the most important residues in the interaction, each contributing significant energy values of -13.45 (electrostatic) and -5.40 kcal/mol (electrostatic and Van der Waals), respectively. The hydroxyl group of the phloroglucinol core of the compound forms a 2.56Å hydrogen bond with the side chain of the carboxylate group of Ile 553. Both Ile 553 and Hie 252 are crucial amino acid residues which chelate with the metal ion in the active site. Distorting the geometry of these ligands could be the reason for the inhibition activity shown by tHGA. The molecular simulation studies supported the bioassay results and served as a good model for understanding the way tHGA binds in the active site of human 5-LOX enzyme.
authors.affiliation: Laboratory of Natural Products, Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Darul Ehsan, Malaysia. khozirah@science.upm.edu.my
authors.forename: Khozirah
authors.initials: K
authors.lastname: Shaari
authors.forename: Velan
authors.initials: V
authors.lastname: Suppaiah
authors.forename: Lam Kok
authors.initials: LK
authors.lastname: Wai
authors.forename: Johnson
authors.initials: J
authors.lastname: Stanslas
authors.forename: Bimo Ario
authors.initials: BA
authors.lastname: Tejo
authors.forename: Daud Ahmad
authors.initials: DA
authors.lastname: Israf
authors.forename: Faridah
authors.initials: F
authors.lastname: Abas
authors.forename: Intan Safinar
authors.initials: IS
authors.lastname: Ismail
authors.forename: Nor Hasifi
authors.initials: NH
authors.lastname: Shuaib
authors.forename: Seema
authors.initials: S
authors.lastname: Zareen
authors.forename: Nordin Hj
authors.initials: NH
authors.lastname: Lajis
mesh_terms: D000098:Acetophenones / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D000893:Anti-Inflammatory Agents / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D001681:Biological Assay; D002470:Cell Survival / Q000187:drug effects; D016166:Free Radical Scavengers / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D006801:Humans; D020128:Inhibitory Concentration 50; D007963:Leukocytes, Mononuclear / Q000201:enzymology; D017997:Leukotriene C4 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016859:Lipoxygenase Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D027821:Rutaceae / Q000737:chemistry*
chemical_list: D000098:Acetophenones; D000893:Anti-Inflammatory Agents; D016166:Free Radical Scavengers; D016859:Lipoxygenase Inhibitors; D010936:Plant Extracts; D017997:Leukotriene C4; D001094:Arachidonate 5-Lipoxygenase