title: Tyrosinase inhibitory activity of flavonoids from Artocarpus heterophyllous.
abstract: BACKGROUND
  Tyrosinase is an oxidoreductase that is very important in medicine and cosmetics because the excessive production of melanin causes hyperpigmentation. The development of novel, effective tyrosinase inhibitors has long been pursued. In preliminary tests, we found that an extract of the wood of Artocarpus heterophyllous (AH) potently inhibited tyrosinase activity.
  
  
  RESULTS
  Two new flavonoids, artocaepin E (1) and artocaepin F (2), were isolated from the wood of AH, together with norartocarpetin (3), artocarpanone (4), liquiritigenin (5), steppogenin (6), and dihydromorin (7). Their structures were elucidated using one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) and mass spectrometry. The absolute configuration of 2 was determined from the circular dichroism (CD) spectrum. Artocarpanone (4) had the most potent tyrosinase inhibitory effect, with an IC50 of 2.0 ± 0.1 μM, followed by artocaepin E (1) and steppogenin (6), with IC50 values of 6.7 ± 0.8 and 7.5 ± 0.5 μM, respectively. A kinetic investigation indicated that 1 showed competitive inhibition, with an inhibition constant (K i) of 6.23 μM.
  
  
  CONCLUSIONS
  These results demonstrate that extracts of the wood of AH and its phytochemical constituents are potential sources for skin-whitening agents.Graphical abstractArtocarmin E (1) and artocarmin F (2) were isolated from the wood of Artocarpus heterophyllous. Their structures were elucidated using nuclear magnetic resonance analysis and mass spectrometric methods.
authors.affiliation: Faculty of Chemistry, University of Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam.
authors.forename: Hai Xuan
authors.initials: HX
authors.lastname: Nguyen
authors.affiliation: Faculty of Chemistry, University of Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam ; Cancer Research Laboratory, Vietnam National University, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam.
authors.forename: Nhan Trung
authors.initials: NT
authors.lastname: Nguyen
authors.affiliation: Faculty of Chemistry, University of Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam.
authors.forename: Mai Ha Khoa
authors.initials: MH
authors.lastname: Nguyen
authors.affiliation: Faculty of Chemistry, University of Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam.
authors.forename: Tho Huu
authors.initials: TH
authors.lastname: Le
authors.affiliation: Faculty of Chemistry, University of Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam.
authors.forename: Truong Nhat
authors.initials: TN
authors.lastname: Van Do
authors.affiliation: Department of Biomedical Sciences, Institute for Research and Executive Education (VNUK), The University of Danang, 41 Le Duan, Haichau District, Danang, Vietnam.
authors.forename: Tran Manh
authors.initials: TM
authors.lastname: Hung
authors.affiliation: Faculty of Chemistry, University of Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam ; Cancer Research Laboratory, Vietnam National University, 227 Nguyen Van Cu, District 5, Ho Chi Minh, Vietnam.
authors.forename: Mai Thanh Thi
authors.initials: MT
authors.lastname: Nguyen
keywords: Artocarpus heterophyllous; Chalcones; Flavonoids; Tyrosinase inhibitors
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