Design, synthesis and cholinesterase inhibitory activity of α-mangostin derivatives.

α-mangostin, a polyphenol xanthone derivative, was mainly isolated from pericarps of the mangosteen fruit (Garcinia mangostana L.). In present investigation, a series of derivatives were designed, synthesised and evaluated in vitro for their inhibitory activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Among the synthesised xanthones, compounds 1, 9, 13 and 16 showed AChE selective inhibitory activity, 15 was a BuChE selective inhibitor while 2, 3, 5, 6, 7, 12 and 14 were dual inhibitors. The most potent inhibitor of AChE was 16 while 5 was the most potent inhibitor of BuChE with IC50 values of 5.26 µM and 7.55 µM respectively.

Phenolic Constituents with Antioxidative, Tyrosinase Inhibitory and Anti-aging Activities from Dendrobium loddigesii Rolfe.

Aqueous ethanol extracts of powdered stems of Dendrobium loddigesii afforded three new phenolics including threo-7-O-ethyl-9-O-(4-hydroxyphenyl)propionyl-guaiacylglycerol (1), (R)-4,5,4'-trihydroxy-3,3',α-trimethoxybibenzyl (2) and (S)-5,5',7-trihydroxy-3',4'-dimethoxyflavanone (3), together with eleven known analogues. Their structures were determined by extensive spectroscopic analysis. To identify natural antioxidants, whitening, and anti-aging agents, the abilities of these phenolics were assessed to scavenge the 1,2-diphenyl-2-picrylhydrazyl (DPPH) radical, their abilities to inhibit tyrosinase production, and their abilities to stimulate collagen production by human dermal fibroblasts-adult (HDFa) assay. It was found that compounds 1, 4-8, 13 and 14 exhibited significant DPPH radical scavenging activities, compound 10 exhibited tyrosinase inhibitory activity (IC50 37.904 µg/mL), and compound 9 showed significant collagen production with an EC50 value of 3.182 µg/mL. These results suggest that phenolic constituents from D. loddigesii may be candidate antioxidants, skin-whitening and/or anti-aging agents.

Stilbenes with anti-inflammatory and cytotoxic activity from the rhizomes of Bletilla ochracea Schltr.

Four new dihydrophenanthrenofuran, bleochranols A-D (1-4), along with 21 known compounds including phenanthrenes (5-14) and bibenzyls (15-25) were isolated and elucidated from the rhizomes of Bletilla ochracea. Combination of 1D/2D NMR techniques and the Electronic Circular Dichroism (ECD) spectroscopy based on the empirical helicity rules, chemical structure of those isolates were determined. All the compounds were evaluated for cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7 and SW480 human cancer cell lines by MTS assay and anti-inflammatory activity by nitric oxide (NO) production in LPS-stimulated RAW 264.7 macrophages. Among the 25 tested compounds, bleochranol A (1) showed remarkable cytotoxic activity against HL-60, A-549, and MCF-7 with IC50 values of 0.24 ±â€¯0.03, 3.51 ±â€¯0.09 and 3.30 ±â€¯0.99 µM respectively. The anti-inflammatory assay showed that compound 12 exhibited most potential activity against NO production in RAW 264.7 macrophages with IC50 2.86 ±â€¯0.17 µM. The results indicated that the main chemical constituents of B. ochracea were phenanthrene and bibenzyl and similar to that of B. striata.

Sesquiterpene amino ether and cytotoxic phenols from Dendrobium wardianum Warner.

A new bibenzyl derivative, dendrocandin V (1) and a new sesquiterpene amino ether, wardianumine A (2), together with eleven known compounds, including phenanthrenes (denbinobin (3), 9,10-dihydro-denbinobin (4), mostatin (5), loddigesiinols A (6)), bibenzyls (moscatilin (7), 5-hydroxy-3,4'-dimethoxybibenzyl (8), 3,4-dihydroxy-5,4'-dimethoxy bibenzyl (9), dendrocandin A (10), gigantol (11), dendrocandin U (12)) and an alkaloids (dihydroshihunine, 13) were isolated from the EtOH extraction of stems of Dendrobium wardianum Warner. Isolation of the new compound 2 indicated that N,N-dimethylethanolamine as the key adduction in the synthesis of dendroxine and its analogs in Dendrobium species. The hypothetical biosynthetic pathway of 2 was then postulated. Inspired by literature and traditional usage of the herbal medicine, some compounds were sent for cytotoxic activity and the results indicated that compounds 1, 3, 4, 5 showed cytotoxic activities against five human cancer cell lines (HL-60, A-549, SMMC-7721, MCF-7, and SW-480) with IC50 from 2.33-38.48µM. Among those compounds, 3 and 4 showed cell line selectivity with strong activity comparable to DDP.