Antioxidant phenolic compounds isolated from wild Pyrus ussuriensis Maxim. fruit peels and leaves.

Thirteen phenolic compounds were isolated from pear (Pyrus ussuriensis Maxim.) peels and leaves extracts by using various column chromatography techniques with a guided DPPH (1,1-diphenyl-2-picrylhydrazyl) radical-scavenging assay, the result of antioxidant activity of phenolic compounds is then verified by measurement of ROS (reactive oxygen species). The isolated compounds were identified as rutin (1), (-)-catechin (2), orobol (3), daidzein (4), tricin 4'-O-[threo-ß-guaiacyl-(7″-O-methyl)-glyceryl] ether (5), tricin 4'-O-[threo-ß-guaiacyl-(7″-O-methyl-9″-O-acetyl)-glyceryl] ether (6), 5,7,3',5'-tetrahydroxyflavanone (7), artselaeroside A (8), trilobatin (9), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (10), quercetin-3-O-(3″-O-galloyl)-α-l-rhamnopyranoside (11), apigenin (12) and quercetin (13) on the basis of nuclear magnetic resonance spectroscopy along with comparison with literature data. Among these compounds, quercetin and quercetin-3-O-(3″-O-galloyl)-α-l-rhamnopyranoside exhibited potent DPPH radical-scavenging activity with IC50 (Half Maximal Inhibitory Concentration) value of 6.06 and 9.60µg/mL, respectively. The results revealed that P. ussuriensis could be used in the fields of food and medicine to prevent human aging diseases.

Identification of insecticidal constituents of the essential oils of Dahlia pinnata Cav. against Sitophilus zeamais and Sitophilus oryzae.

The aim of this research was to determine the chemical composition of the essential oils of Dahlia pinnata, their insecticidal activity against Sitophilus zeamais and Sitophilusoryzae and to isolate insecticidal constituents. Based on bioactivity-guided fractionation, active constituents were isolated and identified as D-limonene, 4-terpineol and α-terpineol. Essential oils and active compounds tested exhibited contact toxicity, with LD50 values ranging from 132.48 to 828.79 µg/cm(2) against S. zeamais and S. oryzae. Essential oils possessed fumigant toxicity against S. zeamais and S. oryzae with LC50 from 14.10 to 73.46 mg/L. d-Limonene (LC50 = 4.55 and 7.92 mg/L) showed stronger fumigant toxicity against target insects. 4-Terpineol (88 ± 8%) and d-limonene (87 ± 5%) showed the strongest repellency against S. zeamais and S. oryzae, respectively. The results indicate that essential oils and insecticidal constituents have potential for development into natural fumigants, insecticides or repellents for control of the stored-product insect pests.

Cloning and functional characterization of a caffeic acid O-methyltransferase from Trigonella foenum-graecum L.

A cDNA encoding an O-methyltransferase (namely FGCOMT1) was identified from the medicinal plant Trigonella foenum-graecum L. The FGCOMT1 enzyme is a functional caffeic acid O-methyltransferase (COMT) and is localized in the cytosol. Kinetic analysis indicated that FGCOMT1 protein exhibited the highest catalyzing efficiency towards 5-hydroxy ferulic acid and caffeic acid as substrates, but did not possess the abilities to methylate either quercetin or tricetin in vitro. Furthermore, transformation of Arabidopsis loss-of-function Atomt1 mutant with a FGCOMT1 cDNA partially complements accumulation of sinapoyl derivatives but did not function to produce the major methylated flavonol isorhamnetin in seeds. The results from this study indicated that FGCOMT1 is a COMT with substrate preference to monomeric lignin precursors but is not involved in the flavonoid methylation in T. foenum-graecum L.

Cloning and functional characterization of a chalcone isomerase from Trigonella foenum-graecum L.

Flavonoids belong to a group of plant natural products with variable phenolic structures and play important roles in protection against biotic and abiotic stress. Fenugreek (Trigonella foenum-graecum L.) seeds and stems contain flavonol glycosides and isoflavone derivatives. Up to now, the molecular features of fenugreek flavonoid biosynthesis have not been characterized. Here we present cloning of a cDNA encoding a chalcone isomerase (namely TFGCHI-1) from the leaves of T. foenum-graecum which convert chalcones to flavanones in vitro. Transformation of Arabidopsis loss-of-function TT5 (CHI) mutant with a TFGCHI-1 cDNA complemented TT5 and produced higher levels of flavonol glycosides than wild-type Col-0.

Cytotoxic metabolites produced by Alternaria no.28, an endophytic fungus isolated from Ginkgo biloba.

From the medicinal plant Ginkgo biloba the fungal endophyte Alternaria no.28 was isolated. Extract of the fungus grown in liquid culture media exhibited marked cytotoxic activity when tested in vitro against brine shrimp (Artemia salina). Eight compounds were isolated from the extract of cultures of this endophytic fungus and were elucidated as alterperylenol (1), altertoxin I (2), alternariol (3), alternariol monomethyl ether (4), tenuazonic acid (5) and its derivative (6), together with ergosterol and ergosta-4, 6, 8, 22-tetraen-3-one by means of spectroscopic analysis. Among them, both 5 and 6 showed significant cytotoxic effects in the brine shrimp bioassy, with mortality rates of 73.6% and 68.9%, respectively, at a concentration of 10 microg x mL(-1), and they were first isolated from endophytic fungi.

Bioactive metabolites produced by Chaetomium globosum, an endophytic fungus isolated from Ginkgo biloba.

A novel cytotoxic chlorinated azaphilone derivative named chaetomugilin D (1), together with three known metabolites, chaetomugilin A (2), chaetoglobosins A (3) and C (4), has been isolated by a bioassay-guided fractionation from the EtOAc extract of the cultures of Chaetomium globosum, an endophytic fungus found in the leaves of Ginkgo biloba. Structure of 1 was established by analyses of spectroscopic methods, including 2D-NMR experiments (COSY, NOESY, HMQC, and HMBC). Compounds 1-4 displayed significant growth inhibitory activity against the brine shrimp (Artemia salina) and Mucor miehei.