α-Pyrones with glucose uptake-stimulatory activity from the twigs of Cryptocarya wrayi.

Five new α-pyrones, cryptowratones A-E (1-5), and five known congeners (6-10), together with four other known compounds 11-14 were isolated from the twigs of Cryptocarya wrayi. The structures of the new compounds were elucidated on the basis of extensive spectroscopic data analysis and ECD calculations. All α-pyrones except 6 were evaluated for their stimulatory effects on glucose uptake in vitro with CHO-K1/GLUT4 cells. The positive control insulin displayed an approximate 42 ± 0.14% promotion on glucose uptake at 25 µM, compared with the CHO-K1/GLUT4 group. Compounds 1a/2a, 2, 3, and 10 showed a more significant stimulation of glucose uptake than insulin (25 µM) by 36 ± 0.08%, 27 ± 0.12%, 28 ± 0.12%, and 25 ± 0.12% at 1.5 µM, respectively. Immunofluorescence assays indicated the glucose uptake-stimulatory activity of α-pyrones might be correlated with increased GLUT4 translocation.

Two new isoquinoline alkaloids from Cryptocarya wrayi and their biological activities.

Two new isoquinoline alkaloids, cryptowrayines A (1) and B (2), along with one known pavine alkaloid (-)-12-hydroxyeschscholtzidine (3), were isolated from the twigs of Cryptocarya wrayi. The structures of new compounds were elucidated by extensive spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Both compounds 1 and 2 exhibited moderate quinone reductase inducing activity in Hepa 1c1c7 cells.

Tyrosinase inhibitors from the leaves of Eucalyptus globulus.

A new isoiphionane sesquiterpene, named (3S, 5S, 7S, 10R)-3, 11-dihydroxyisoiphion-4-one (1), two new phloroglucinol glycosides, named eucalglobuside A (2) and eucalglobuside B (3), along with 15 known compounds were isolated from the leaves of Eucalyptus globulus. Their structures were elucidated based on extensive spectroscopic analysis and in comparison with literature data. The absolute configuration of compound 1 was determined by ECD calculation. All isolates were evaluated their inhibitory activities against the mushroom tyrosinase. As a result, three sesquiterpenoids, 1, 5ß, 11-dihydroxy-iphionan-4-one (5), and (-)-globulol (8), exhibited the most potent activities with IC50 values of 14.17 µM, 10.08 µM and 9.79 µM, respectively.

Artopithecins A-D, Prenylated 2-Arylbenzofurans from the Twigs of Artocarpus pithecogallus and Their Tyrosinase Inhibitory Activities.

Four new prenylated 2-arylbenzofurans, namely artopithecins A-D (1-4), together with five known compounds (5-9) were isolated from the twigs of Artocarpus pithecogallus for the first time. Their structures were elucidated based on extensive spectroscopic analysis and in comparison with literature data. All isolates were evaluated for their inhibitory activities against mushroom tyrosinase. Compounds 3 and 4 displayed significant tyrosinase inhibitory activities with IC50 values of 37.09±0.33 and 38.14±0.21 µM, respectively.

Prenylflavonoids from the Twigs of Artocarpus nigrifolius.

Two new prenylated flavones, artocarnin A (2) and carpachromenol (12), together with 13 known prenylflavonoids (1, 3-11, 13-15) were isolated from the twigs of Artocarpus nigrifolius for the first time. Their structures were elucidated by high resolution-electrospray ionization (HR-ESI)-MS, NMR spectroscopic analysis, and in comparison with the reported data. Compounds 1-15 were evaluated for their antiproliferative effects against SiHa and SGC-7901 human cancer cell lines in vitro. The most active compound, eleocharin A (10), showed significant cytotoxicity on SiHa cells (IC50=0.7±0.1 µM) and inhibitory activity against SGC-7901 cells (IC50=8.3±0.2 µM) and could be considered as potential lead compound for further development of novel anti-tumor agents.