Weed Suppressing Potential and Isolation of Potent Plant Growth Inhibitors from Castanea crenata Sieb. et Zucc.

This study isolated, determined, and quantified plant growth inhibitors in Japanese chestnut (Castanea crenata Sieb. et Zucc), a deciduous species native to Japan and Korea. In laboratory assays, C. crenata leaves showed strong inhibition on germination and seedling growth of Echinochloa crus-galli (barnyardgrass), Lactuca sativa (lettuce), and Raphanus sativus (radish). Laboratory and greenhouse trials showed that leaves of C. crenata appeared as a promising material to manage weeds, especially the dicot weeds. By GC-MS and HPLC analyses, gallic, protocatechuic, p-hydroxybenzoic, caffeic, ferulic, ellagic, and cinnamic acids were identified and quantified, of which ellagic acid was present in the highest quantity (2.36 mg/g dried leaves). By column chromatography and spectral data (¹H- and 13C-NMR, IR, and LC-MS) analysis, a compound identified as 2α,3ß,7ß,23-tetrahydroxyurs-12-ene-28-oic acid (1) was purified from the methanolic leaf extract of C. crenata (0.93 mg/g dried leaves). This constituent showed potent inhibition on growth of E. crus-galli, a problematic weed in agricultural practice. The inhibition of the compound 1 (IC50 = 2.62 and 0.41 mM) was >5 fold greater than that of p-hydroxybenzoic acid (IC50 = 15.33 and 2.11 mM) on shoot and root growth of E. crus-galli, respectively. Results suggest that the isolated the compound 1 has potential to develop natural herbicides to manage E. crus-galli. This study is the first to isolate and identify 2α,3ß,7ß,23-tetrahydroxyurs-12-ene-28-oic acid in a plant and report its plant growth inhibitory potential.

Phenolic Compounds and Antioxidant Activity of Phalaenopsis Orchid Hybrids.

Phalaenopsis spp. is the most commercially and economically important orchid, but their plant parts are often left unused, which has caused environmental problems. To date, reports on phytochemical analyses were most available on endangered and medicinal orchids. The present study was conducted to determine the total phenolics, total flavonoids, and antioxidant activity of ethanol extracts prepared from leaves and roots of six commercial hybrid Phalaenopsis spp. Leaf extracts of "Chian Xen Queen" contained the highest total phenolics with a value of 11.52 ± 0.43 mg gallic acid equivalent per g dry weight and the highest total flavonoids (4.98 ± 0.27 mg rutin equivalent per g dry weight). The antioxidant activity of root extracts evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay and ß-carotene bleaching method was higher than those of the leaf extracts. Eleven phenolic compounds were identified, namely, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, vanillin, ferulic acid, sinapic acid, p-coumaric acid, benzoic acid, and ellagic acid. Ferulic, p-coumaric and sinapic acids were concentrated largely in the roots. The results suggested that the root extracts from hybrid Phalaenopsis spp. could be a potential source of natural antioxidants. This study also helps to reduce the amount of this orchid waste in industrial production, as its roots can be exploited for pharmaceutical purposes.

Phenolic Profiles and Antioxidant Activity of Germinated Legumes.

Bioactive compounds, which are naturally produced in plants, have been concerned with the food and pharmaceutical industries because of the pharmacological effects on humans. In this study, the individual phenolics of six legumes during germination and antioxidant capacity from sprout extracts were determined. It was found that the phenolic content significantly increased during germination in all legumes. Peanuts showed the strongest antioxidant capacity in both the DPPH• (1,1-diphenyl-2-picrylhydrazyl) method and the reducing power assay (32.51% and 84.48%, respectively). A total of 13 phenolic acids were detected and quantified. There were 11 phenolic constituents identified in adzuki beans; 10 in soybeans; 9 in black beans, mung beans, and white cowpeas; and 7 compounds in peanuts. Sinapic acid and cinnamic acid were detected in all six legume sprouts, and their quantities in germinated peanuts were the highest (247.9 µg·g-1 and 62.9 µg·g-1, respectively). The study reveals that, among the investigated legumes, germinated peanuts and soybeans obtained maximum phenolics and antioxidant capacity.

Efficacy of extracting solvents to chemical components of kava (Piper methysticum) roots.

The chemical composition of kava (Piper methysticum) lactones and various phytochemicals obtained following the sonication of ground kava roots extracted in the solvents hexane, chloroform, acetone, ethanol, methanol and water, respectively, was analyzed. Eighteen kava lactones, cinnamic acid bornyl ester and 5,7-dimethoxy-flavanone, known to be present in kava roots, were identified, and seven compounds, including 2,5,8-trimethyl-1-naphthol, 5-methyl-1-phenylhexen-3-yn-5-ol, 8,11-octadecadienoic acid-methyl ester, 5,7-(OH)(2)-4'-one-6,8-dimethylflavanone, pinostrobin chalcone and 7-dimethoxyflavanone-5-hydroxy-4', were identified for the first time. Glutathione (26.3 mg/g) was found in the water extract. Dihydro-5,6-dehydrokavain (DDK) was present at a higher level than methysticin and desmethoxyyagonin, indicating that DDK is also a major constituent of kava roots. Acetone was the most effective solvent in terms of maximum yield and types of kava lactones isolated, followed by water and chloroform, whereas hexane, methanol, and ethanol were less effective as solvents. Total phenolic and antioxidant activity varied among the extracting solvents, with acetone and chloroform producing the highest effects, followed by water, while methanol, ethanol and hexane were less effective.

Antioxidant and antibacterial activities of Rumex japonicus HOUTT. Aerial parts.

We evaluated total phenolic content, antioxidant activity, reducing power and antibacterial activity of ethanol, hexane, chloroform, ethyl acetate and aqueous extracts of aerial parts of Rumex japonicus HOUTT. The ethyl acetate extract had the highest amount of phenolic compounds. It also exhibited the highest reducing power and antioxidant activity when assayed by the 1,1-diphenyl-2-picrylhydrazyl (DPPH), beta-carotene bleaching and superoxide radical methods. The ethyl acetate extract possessed the strongest antibacterial activity against Bacillus subtilis, B. cereus and E. coli. GC-MS analysis indicated that ethyl acetate extract contained a variety of phenolic compounds. HPLC analysis showed that pyrogallol was the predominant phenolic compound in this extract. Thus, our study verified that the ethyl acetate extract has strong antioxidant and antibacterial activities which are correlated with its high level of phenolic compounds, particularly pyrogallol and pyrocatechin. This extract of R. japonicus aerial parts can be utilized as an effective and safe source of antioxidants.