Melanogenesis Inhibitors from the Endophytic Fungus Aspergillus amstelodami

Two new compounds, named 3,4-dimethoxyphenyl α-d-ribofuranoside (1) and 3β-(β-d-glucopyranosyloxy)olean-12-ene-23,28,30-trioic acid (2), together with thirteen known compounds, were isolated from the white beans culture of the marine derived endophytic fungus Aspergillus amstelodami. Structure elucidation of the new compounds was carried out by one-, two-dimensional spectroscopy, and high resolution electrospray ionization mass. The antimelanogenic and anti-allergic activity of the isolated compounds were investigated. Compounds 4, 7, 1, 3, 11, 6 and 9 selectively suppressed melanin production in B16 melanoma cells, using arbutin as a positive control. Their IC₅₀ values were 30.8±5.57, 38.5±6.08, 52.6±6.64, 98.0±1.16, 100.4±3.05, 112.0±0.22 and 144.7±2.35 μm, respectively, while that of arbutin was 151.7±1.27 μm. The tested compounds did not show any significant anti-allergic activity in RBL-2H3 cells, as compared to quercetin.