Thesis (M.Sc.)--Chulalongkorn University, 2002

The preliminary bioassay results indicated that the hexane and chloroform extracts of hydrocotyle umbellata linn. were biologically active. Nine substances were isolated and elucidated their structural formulas by means of physical properties, chemical reactions and spectroscopic evidences as a mixture of essential oils (chamigrene, alpha-bergamotene, alpha-santalol, germacrene D, beta-caryophyllene and beta-pinene), a mixture of long chain carboxylic acids, a mixture of long chain aliphatic alcohols, a mixture of long chain aliphatic esters, a mixture of stigmasterol and stigmasta-7,25-dien-3-ol, stigmasteryl-3-D-glucopyranoside, beta-D-glucopyranosyl tetratriacontan-2,4-dienoate and methyl oleanolate 3-O-( beta-D-glucopyranoside)[subscript 3]. The last two compounds were disclosed to be new naturally occurring compounds. Besides, the hydrodistillation of the fresh whole plants was conducted to gain the essential oil. Longicyclene, alpha-bergamotene, beta-caryophyllene, 1H-benzoheptene,2,4alph,5,6,7,8,9,9alpha-octahydro 3,5,5-trimethyl-9-methylene-(4alphaS-cis) and alpha-santalol were analyzed as its composition. This is the first report of the chemical constituents from this plant. Plant growth inhibitory study against seedling of mimosa pigra Linn., disclosed methyl oleanolate glycoside showed the highest root inhibitory activity 70% at 1000 ppm, followed by beta-D-glucopyranosyl tetratriacontan-2,4-dienoate and essential oil from fresh plants, which gave 63% and 46% inhibitory activities, respectively. Furthermore, seedling growth inhibitory effect against selected plants: echinochloa crus-galli beauv., pennisetum pedicellatum schult., lactuca sativa linn., trianthema portulacastrum linn. and bidens pilosa linn. were also investigated. Methyl oleanolate 3-O-(beta-D-glucopyranoside)[subscript 3] exhibited the highest inhibitory effect activity against root growth on these studied plants.