title: Tyrosinase inhibitors from Rhododendron collettianum and their structure-activity relationship (SAR) studies.
abstract: A new coumarinolignoid 8'-epi-cleomiscosin A (1) together with the new glycoside 8-O-beta-D-glucopyranosyl-6-hydroxy-2-methyl-4H-1-benzopyrane-4-one (2) have been isolated from the aerial parts of Rhododendron collettianum and their structures determined on the basis of spectroscopic evidences. Tyrosinase inhibition study of these compounds and their structure-activity relationship (SAR) were also investigated. The compounds exhibited potent to mild inhibition activity against the enzyme. Especially, the compound 1 showed strong inhibition (IC50=1.33 microM) against the enzyme tyrosinase, as compared to the standard tyrosinase inhibitors kojic acid (IC50=16.67 microM) and L-mimosine (IC50=3.68 microM), indicating its potential used for the treatment of hyperpigmentation associated with the high production of melanocytes.
authors.affiliation: HEJ Research Institute of Chemistry, University of Karachi, Karachi, Pakistan. vuahmad@cyber.net.pk
authors.forename: Viqar Uddin
authors.initials: VU
authors.lastname: Ahmad
authors.forename: Farman
authors.initials: F
authors.lastname: Ullah
authors.forename: Javid
authors.initials: J
authors.lastname: Hussain
authors.forename: Umar
authors.initials: U
authors.lastname: Farooq
authors.forename: Muhammad
authors.initials: M
authors.lastname: Zubair
authors.forename: Mahmud Tareq Hassan
authors.initials: MT
authors.lastname: Khan
authors.forename: Muhammad Iqbal
authors.initials: MI
authors.lastname: Choudhary
mesh_terms: D001578:Benzopyrans / Q000737:chemistry / Q000494:pharmacology*; D003374:Coumarins / Q000737:chemistry / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006027:Glycosides / Q000737:chemistry / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D010936:Plant Extracts / Q000737:chemistry; D029793:Rhododendron / Q000737:chemistry*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
chemical_list: C499804:8'-epi-cleomiscosin A; C499806:8-O-beta-D-glucopyranosyl-6-hydroxy-2-methyl-4H-1-benzopyrane-4-one; D001578:Benzopyrans; D003374:Coumarins; D004791:Enzyme Inhibitors; D006027:Glycosides; D010936:Plant Extracts; D014442:Monophenol Monooxygenase