Acetylcholine esterase inhibitory activity of green synthesized nanosilver by naphthopyrones isolated from marine-derived Aspergillus niger.

Aspergillus niger metabolites exhibited a wide range of biological properties including antioxidant and neuro-protective effects and some physical properties as green synthesis of silver nanoparticles AgNP. The present study presents a novel evidence for the various biological activities of green synthesized AgNPs. For the first time, some isolated naphtho-γ-pyrones from marine-derived Aspergillus niger, flavasperone (1), rubrofusarin B (2), aurasperone A (3), fonsecinone A (4) in addition to one alkaloid aspernigrin A (7) were invistigated for their inhibitory activity of acetylcholine esterase AChE, a hallmark of Alzheimer's disease (AD). The ability to synthesize AgNPs by compounds 3, 4 and 7 has been also tested for the first time. Green synthesized AgNPs were well-dispersed, and their size was ranging from 8-30 nm in diameter, their morphology was obviously spherical capped with the organic compounds. Further biological evaluation of their AChE inhibitory activity was compared to the parent compounds. AgNps dramatically increased the inhibitory activity of Compounds 4, 3 and 7 by 84, 16 and 13 fold, respectively to be more potent than galanthamine as a positive control with IC50 value of 1.43 compared to 0.089, 0.311 and 1.53 of AgNPs of Compounds 4, 3 and 7, respectively. Also compound 2 showed moderate inhibitory activity. This is could be probably explained by closer fitting to the active sites or the synergistic effect of the stabilized AgNPs by the organic compouds. These results, in addition to other intrinsic chemical and biological properties of naphtho-γ-pyrones, suggest that the latter could be further explored with a view towards other neuroprotective studies for alleviating AD.

Antiproliferative activity of stilbene derivatives and other constituents from the stem bark of Morus nigra L.

The antiproliferative activities of 2',3,4',5,5'-pentahydroxy-cis-stilbene 1, resveratrol 2, oxyresveratrol 3, norartocarpetin 4, kuwanon C 5, morusin 6, cudraflavone A7, kuwanon G 8, albafuran C 9, mulberrofuran G 10, 3-acetyl-O-α-amyrin 11, 3-acetyl-O-ß-amyrin 12, ursolic acid-3-O-acetate 13 and uvaol 14, previously identified from the barks of Morus nigra L., were investigated against HepG2 and MCF-7 cell lines. In addition, a series of methylated stilbenes 15-19 were prepared using compounds 1-3 and their antiproliferative effects were similarly investigated. The structure of a new 2',3,4'-trimethoxy-5-hydroxy-trans-stilbene 19 was elucidated using spectroscopic techniques. It showed remarkable activity against MCF-7 cells with IC50 12.5 µM. However, kuwanon C (5) showed the highest antiproliferative activity with IC50 3.92 and 9.54 µM against MCF-7 and HepG2, respectively.

Cytotoxic constituents of Alocasia macrorrhiza.

An indole alkaloid, 2-(5-hydroxy-1H-indol-3-yl)-2-oxo-acetic acid (1) isolated for the first time from nature, in addition to the nine known compounds 5-hydroxy-1H-indole-3-carboxylic acid methyl ester (2), alocasin B (3), hyrtiosin B (4), α-monopalmitin (5), 1-O-ß-D-glucopyranosyl-(2S, 3R, 4E, 8Z)-2-[(2(R)-hydroctadecanoyl) amido]-4,8-octadecadiene-1,3-diol (6), 3-epi-betulinic acid (7), 3-epi-ursolic acid (8), ß-sitosterol (9) and ß-sitosterol 3-O-ß-D-glucoside (10) were isolated from the rhizomes of Alocasia macrorrhiza (Araceae). Their structures were elucidated by 1D and 2D NMR spectroscopic data. Of these compounds, 6 exhibited the strongest cytotoxicity against the four tested human cancer cell lines (IC50 of about 10 µM against Hep-2 larynx cancer cells).