[Structures of oligostilbenoids in dipterocarpaceaeous plants and their biological activities]

Chemical composition and biological activities of Dipterocarpus cornutus Dyer essential oil

The design of this study was developed to examine the chemical composition, anticholinesterase and anti-inflammatory inhibitory activities of the essential oil of Dipterocarpus cornutus Dyer from Malaysia. Gas chromatography (GC) and gas chromatography/mass spectrometry (GC-MS) analysis of the essential oil revealed 20 components, representing 94.6% of the oil. The major components identified were α-gurjunene (50.6%), α-selinene (8.3%), spathulenol (5.7%), and bicyclogermacrene (5.4%). Anticholinesterase and anti-inflammatory activity were also evaluated using the Ellman method and lipoxygenase (LOX) enzyme, respectively, in which the essential oil revealed weak inhibitory activity against the acetylcholinesterase (AChE) (I%: 30.2%) and butyrylcholinesterase (BChE) (I%: 32.5%), while moderate inhibitory activity was reported in the LOX (I%: 70.2%). The approach adopted in this study and results are reported for the first time which could be useful for the characterization, pharmaceutical and therapeutic applications of the essential oil from Dipterocarpus genus.

Update on Phytochemistry and Pharmacology of Naturally Occurring Resveratrol Oligomers

Resveratrol oligomers (REVs), a major class of stilbenoids, are biosynthesized by regioselective oxidative coupling of two to eight units of resveratrol monomer. Due to their unique structures and pleiotropic biological activities, natural product chemists are increasingly focusing on REVs in the last few decades. This study presents a detailed and thorough examination of REVs, including chemical structures, natural resources, and biological activities, during the period of 2010–2017. Ninety-two new REVs compounds, including 39 dimers, 23 trimers, 13 tetramers, six resveratrol monomers, six hexamers, four pentamers, and one octamer, have been reported from the families of Dipterocarpaceae, Paeoniaceae, Vitaceae, Leguminosae, Gnetaceae, Cyperaceae, Polygonaceae Gramineae, and Poaceae. Amongst these families, Dipterocarpaceae, with 50 REVs, accounts for the majority, and seven genera of Dipterocarpaceae are involved, including Vatica, Vateria, Shorea, Hopea, Neobalanocarpus, Dipterocarpus, and Dryobalanops. These REVs have shown a wide range of bioactivities. Pharmacological studies have mainly focused on potential efficacy on tumors, bacteria, Alzheimer’s disease, cardiovascular diseases, and others. The information updated in this review might assist further research and development of novel REVs as potential therapeutic agents.

Quantitative Determination of Stilbenoids and Dihydroisocoumarins in Shorea roxburghii and Evaluation of Their Hepatoprotective Activity

A simultaneous quantitative analytical method for 13 stilbenoids including (-)-hopeaphenol (1), (+)-isohopeaphenol (2), hemsleyanol D (3), (-)-ampelopsin H (4), vaticanols A (5), E (6), and G (7), (+)-α-viniferin (8), pauciflorol A (9), hopeafuran (10), (-)-balanocarpol (11), (-)-ampelopsin A (12), and trans-resveratrol 10-C-β-d-glucopyranoside (13), and two dihydroisocoumarins, phayomphenols A₁ (14) and A₂ (15) in the extract of Shorea roxburghii (dipterocarpaceae) was developed. According to the established protocol, distributions of these 15 polyphenols (1-15) in the bark and wood parts of S. roxburghii and a related plant Cotylelobium melanoxylon were evaluated. In addition, the principal polyphenols (1, 2, 8, 13-15) exhibited hepatoprotective effects against d-galactosamine (d-galN)/lipopolysaccharide (LPS)-induced liver injury in mice at a dose of 100 or 200 mg/kg, p.o. To characterize the mechanisms of action, the isolates were examined in in vitro studies assessing their effects on (i) d-GalN-induced cytotoxicity in primary cultured mouse hepatocytes; (ii) LPS-induced nitric oxide (NO) production in mouse peritoneal macrophages; and (iii) tumor necrosis factor-α (TNF-α)-induced cytotoxicity in L929 cells. The mechanisms of action of these polyphenols (1, 2, and 8) were suggested to be dependent on the inhibition of LPS-induced macrophage activation and reduction of sensitivity of hepatocytes to TNF-α. However, none of the isolates reduced the cytotoxicity caused by d-GalN.

Occurrence of stilbene oligomers in Cyperus rhizomes

Investigation of the chemical constituents of Rhizoma Cyperi (Cyperus rotundus Linneus)resulted in the isolation of novel enantiomeric andmeso-stilbene trimers [i.e., (+)- and (−)-(E)-cyperusphenol A (1, 2 respectively) and (E)-mesocyperusphenol A (3)], a trimer bearing a novelhexacyclic ring system [cyperusphenol B (5)], aswell as knownstilbenoids (cyperusphenols C (4)and D (6), scirpusins A (7) and B (8), and piceid (9)) and luteolin. HPLC was used for the opticalresolution of 1 and 2 as well as for the identification of cooccurrence of enantiomers of 7. Thestructures of the isolates were established by spectroscopic analyses, including a detailed NMRspectroscopic investigation. The isolates were evaluated in terms of their antiproliferative activityemploying the Jurkat cell line (human T-cell leukemia cells), while the IC50 potencies of aracemate of 1 and 2, 3, 5, and 6 were estimated as 27.4, 40.5, 26.4, and 26.3 μM, respectively. Thesuppression of cell growth by 6 was due to the induction of apoptosis,whichwas characterized bynuclear changes and PARP-1 cleavage determined bywestern blotting.We also evaluated the freeradical scavenging activity of the isolates.

Resveratrol derivatives from Vatica albiramis

Three new stilbene derivatives, albiraminols A (1) (resveratrol hexamer), B (2) (resveratrol dimer), and vatalbinoside F (3) (mono-glucoside of resveratrol dimer), along with malibatol were isolated from acetone soluble portions of the stem of Vatica albiramis. The structures of the isolates were established on the basis of spectroscopic analyses, including a detailed NMR spectroscopic investigation. The biosynthetic aspects of the isolates are discussed in this paper. Compound 1 is composed of tetrameric resveratrol (vaticanol B (1A)) and dimeric resveratrol (1B) and is the first instance of the resveratrol derivative bearing a 5,6,11,12-tetrahydro-5,11-epoxydibenzo[a,e][8]annulene ring system. Compound 2 possesses a novel 4,5-dihydro-13-oxabenzo[3,4]azuleno[7,8,1-jkl]phenanthrene skeleton in the framework.