Bioactive Bibenzyl Derivatives and Fluorenones from Dendrobium nobile

Abstract

Bioassay-guided fractionation of the 60% ethanol extract of the stems of Dendrobium nobile using the DPPH assay led to the isolation of two new bibenzyl derivatives, nobilin D (1) and nobilin E (2), and a new fluorenone, nobilone (3), together with seven known compounds (4-10). Their structures were determined on the basis of spectroscopic analyses. Compounds 1, 2, 4, 7, 8, and 10 exhibited significant antioxidant activity higher than or equivalent to vitamin C in the DPPH assay, and compounds 1, 3, 4, and 7-10 displayed higher antioxidant activity than vitamin C in the ORAC assay. Compounds 1, 2, and 10 also exhibited stronger inhibitory effects on NO production than resveratrol.

Marker Constituents of the Natural Antioxidant Eucalyptus Leaf Extract for the Evaluation of Food Additives

“…34,35) Among polyphenols, including flavonol glycosides and hydrolyzable tannins characterized in the extract, bioactive oenothein B (2) might be a significant marker characteristic of the E. globulus leaf, because it is a rare natural product with a unique structure and can be detected easily without interference from other peaks on a reversed-phase HPLC chromatogram in a gradient mode with 5% AcOH and MeOH (Fig. 1).…”

Anti-inflammatory phenanthrene derivatives from stems of Dendrobium denneanum

“…These are widely used in traditional Chinese medicine for recovery of gastric motility and promoting gastric acid secretion in the stomach, as well as promoting secretion of saliva, improving eyesight, and reducing fever (Shu et al, 2004). The plants of this genus contain bibenzyls (Li et al, 2009), phenanthrenes (Lee et al, 2009;Wang et al, 2009), anthraquinones (Lin et al, 2001), fluoro-derivatives (Zhang et al, 2007), coumarins (Zhang et al, 2005), sesquiterpenes (Zhang et al, 2008) and alkaloids (Wang and Zhao, 1985). Some of these compounds have also been reported as having antioxidant, anti-inflammatory (Zhang et al, 2007), antifibrotic (Yang et al, 2007a), immunomodulatory ) and anti-platelet aggregation activities (Fan et al, 2001).…”

Total synthesis of amorfrutin B via a Pd-catalyzed regioselective geranyl migration-decarboxylation-cycloaromatization cascade

“…18 Regioselective acylation of ketoester 6 by Claisen condensation reaction with dihydrocinnamoyl chloride 8 in the presence of magnesium chloride and pyridine gave the corresponding diketoester-dioxinone 9 in a satisfactory yield. Subsequent reaction of diketoester-dioxinone 9 with Pd(PPh 3 ) 4 and cesium carbonate resulted in decarboxylative geranyl migration and formation of the resorcylate 10. Finally, phenol methylation of 10 and saponification of resulting 13 gave amorfrutin B.…”

“…Molecules containing a bibenzyl unit were found to occur widely in natural products [1][2][3] and display diversified biological activities such as antioxidant, 4 antimicrobial, 5 antifungal, 6 antitumor, 7 and cytotoxic. 8 Within this class, amorfrutins were isolated in 1981 by Mitscher et al., from the ethanolic extracts of the fruits, stems, and leaves of Amorpha fruticosa, a shrub originating in North America, China and Korea.…”