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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 IC 50  of 2.0 ± 0.1 μM, followed by artocaepin E ( 1 ) and steppogenin ( 6 ), with IC 50  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 abstract   Artocarmin 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 methodsElectronic supplementary material  The online version of this article (doi:10.1186/s13065-016-0150-7) contains supplementary material, which is available to authorized users.

Tyrosinase inhibitory activity of flavonoids from Artocarpus heterophyllous