A novel Mg(2+)-dependent O-methyltransferase in the phenylpropanoid metabolism of Mesembryanthemum crystallinum. (1/5)
Upon irradiation with elevated light intensities, the ice plant (Mesembryanthemum crystallinum) accumulates a complex pattern of methylated and glycosylated flavonol conjugates in the upper epidermal layer. Identification of a flavonol methylating activity, partial purification of the enzyme, and sequencing of the corresponding peptide fragments revealed a novel S-adenosyl-l-methionine-dependent O-methyltransferase that was specific for flavonoids and caffeoyl-CoA. Cloning and functional expression of the corresponding cDNA verified that the new methyltransferase is a multifunctional 26.6-kDa Mg(2+)-dependent enzyme, which shows a significant sequence similarity to the cluster of caffeoyl coenzyme A-methylating enzymes. Functional analysis of highly homologous members from chickweed (Stellaria longipes), Arabidopsis thaliana, and tobacco (Nicotiana tabacum) demonstrated that the enzymes from the ice plant, chickweed, and A. thaliana possess a broader substrate specificity toward o-hydroquinone-like structures than previously anticipated for Mg(2+)-dependent O-methyltransferases, and are distinctly different from the tobacco enzyme. Besides caffeoyl-CoA and flavonols, a high specificity was also observed for caffeoylglucose, a compound never before reported to be methylated by any plant O-methyltransferase. Based on phylogenetic analysis of the amino acid sequence and differences in acceptor specificities among both animal and plant O-methyltransferases, we propose that the enzymes from the Centrospermae, along with the predicted gene product from A. thaliana, form a novel subclass within the caffeoyl coenzyme A-dependent O-methyltransferases, with potential divergent functions not restricted to lignin monomer biosynthesis. (+info)Bioactive constituents from Chinese natural medicines. XIV. New glycosides of beta-carboline-type alkaloid, neolignan, and phenylpropanoid from Stellaria dichotoma L. var. lanceolata and their antiallergic activities. (2/5)
A new beta-carboline-type alkaloidal glycoside, glucodichotomine B, four new neolignan glycosides, dichotomosides A, B, C, and D, and a new phenylpropanoid glycoside, dichotomoside E, were isolated from a Chinese natural medicine, the roots of Stellaria dichotoma L. var. lanceolata. The structures of the new glycosides were determined on the basis of chemical and physicochemical evidence. Among them, dichotomoside D inhibited the release of beta-hexosaminidase (IC(50)=64 microM) as well as tumor necrosis factor-alpha and interleukin-4 (IC(50)=16, 34 microM) in RBL-2H3 cells. These findings suggest that dichotomoside D is more effective against the late-phase reactions in type I allergy than in the immediate phase. (+info)The regulation of cell wall extensibility during shade avoidance: a study using two contrasting ecotypes of Stellaria longipes. (3/5)
(+info)Anti-hepatitis B virus activity of chickweed [Stellaria media (L.) Vill.] extracts in HepG2.2.15 cells. (4/5)
(+info)Quality assessment and anti-obesity activity of Stellaria media (Linn.) Vill. (5/5)
(+info)Stellaria, in a medical context, refers to a genus of plants known as Chickweed, specifically Stellaria media, which has been used in traditional medicine for its anti-inflammatory and demulcent properties, often applied topically to treat skin irritations or ingested for internal disorders such as bronchitis and irregularities in the gastrointestinal system. However, it's essential to note that the use of such herbal remedies should be under the guidance of a healthcare professional, as they can interact with other medications and have potential side effects.
'Stellaria' is not a term that has a specific medical definition. It is a genus name for several species of plants in the family Caryophyllaceae, also known as chickweeds. Some people may use it in a alternative medicine context to refer to these plants or their extracts, but there is no established medical use or meaning for the term 'Stellaria'. If you have any questions about a specific medical condition or treatment, I would recommend consulting with a healthcare professional.