Shiow Chyn Huang

Carbazole alkaloids from Clausena excavata and their biological activity

Five new carbazole alkaloids, clausines B, E, H, I and K, as well as 22 known compounds, were isolated from the stem bark of Clausena excavata. The structures were established from spectral data and chemical transformation. These compounds showed significant inhibition of rabbit platelet aggregation and caused vasocontraction. The crude methanol extract, partitioned layers and chromatographic fractions revealed the presence of promotive and inhibitive constituents, simultaneously. These results might explain the philosophy of use in Chinese medicine, in that the dose and content variation in a prescription produced different, promotive or inhibitive, effects on therapy.

Alkaloidal and other constituents from the root bark of Clausena excavata

Ten new carbazole alkaloids, clausine-M, -N, -O, -P, -Q, -R, -S, -U, -V and clausenatine-A, together with 39 known compounds were isolated and identified from the acetone extract of the root bark of Clausena excavata. Their structures have been elucidated by spectroscopic analyses. This is the first report of a decarboxylated carbazole alkaloid from a natural source. The presence of a C23-skeleton carbazole alkaloid in a plant of Clausena genus is also reported for the first time.

Two coumarins from the root bark of Clausena excavata

Two new pyrano-coumarins, claucavatin-A and -B, together with eight known coumarins and two known flavonoids were isolated and identified from the acetone extract of the root bark of Clausena excavata. Their structures were elucidated by the spectroscopic analyses.

Carbazole-pyranocoumarin dimer and binary carbazole alkaloid from Clausena excavata

Abstract Examination of the extract from the stem bark and root bark of Clausena excavata , a binary carbazole alkaloid, clausenamine-A ( 1 ), and a carbazole-pyranocoumarin dimer, carbazomarin-A ( 2 ), were isolated, respectively. Their structures were elucidated by spectroscopic analyses.

Antiplatelet actions of some coumarin compounds isolated from plant sources

Xanthyletin, xanthoxyletin, suberosin (all from Citrus grandis), aurapten (from Severinia huxifolia) and poncitrin (from Poncirus trifoliata) were isolated and their chemical structures were characterized to be coumarin compounds. All these coumarin compounds except xanthyletin inhibited the aggregation and ATP release of rabbit platelets induced by arachidonic acid, collagen, ADP, platelet-activating factor (PAF) or U46619 (a thromboxane A2 analog). Thrombin-induced ATP release, but not the aggregation, was also inhibited by these compounds. Xanthyletin inhibited only platelet aggregation induced by arachidonic acid and collagen, while poncitrin inhibited that caused by PAF more markedly than other coumarin compounds. The thromboxane B2 formation in washed platelets caused by arachidonic acid and collagen was suppressed by these coumarin compounds. The phosphoinositide breakdown caused by collagen and PAF was also inhibited by these compounds. They did not affect fibrinogen-induced aggregation of elastase-treated platelets. These antiplatelet actions were immediate, reversible by washout and independent on the incubation time (except suberosin). Antiaggregating effect was also studied by an electrical impedance method and the inhibitory effect of coumarin compounds on the whole blood and platelet-rich plasma was much less than that of platelet suspension in the aggregation induced by collagen, PAF and ADP. It is concluded that the antiplatelet actions of these coumarin compounds are due to the inhibition on thromboxane A2 formation and phosphoinositides breakdown.

Carbazole alkaloids from stem bark of Clausena excavata

Abstract Four new carbazole alkaloids, clausines A, C, G and J were identified as 3-formyl-2-hydroxy-8-methoxycarbazole 3-carbomethoxy-7-methoxycarbazole, 3-carbomethoxy-1-hydroxy-6-methoxycarbazole and 3-formyl-1, 7-dihydroxy-6-methoxycarbazole, respectively, from a methanol extract of the stem bark of Clausena excavata . Structures were established by spectroscopic analyses.

Constituents of the Roots of Clausena lansium and Their Potential Anti-inflammatory Activity

Eight new carbazole alkaloids, claulamines C (1), D (2), and E (5) and clausenalines B-F (3, 4, 6-8), four new coumarins, clausemarins A-D (9-12), and 43 known compounds were isolated from the roots of Clausena lansium. The structures of the new compounds were established on the basis of 2D-NMR spectroscopic analysis, and their absolute configurations were established from their ECD spectra. The configuration of wampetin was revised as E using a NOESY experiment. Most of the isolated compounds were evaluated for their potential anti-inflammatory activity. The results showed that compounds 9, 13-18, and 20-22 exhibited strong inhibition of superoxide anion generation with IC50 values ranging from 1.9 to 8.4 μM, while compounds 18, 19, and 21 inhibited elastase release with IC50 values in the range from 2.0 to 6.9 μM.

Structure and synthesis of clausenaquinone-a. A novel carbazolequinone alkaloid and bioactive principle from clausena excavata

Abstract A new carbazolequinone alkaloid, clausenaquinone-A, has been isolated from the stem bark of Clausena excavata. The structure has been established from spectral data and total synthesis. Clausenaquinone-A shows potent inhibitory activity of the rabbit platelet aggregation as well as cytotoxicity in HCT-8, RPMI-7951, and TE671 tumor cells.

A flavonoid and indole alkaloid from flowers of Murraya paniculata

Abstract A new naturally occurring flavonoid, 3,5,7,3′,4′,5′-hexamethoxyflavone, and a new indole alkaloid, murrayaculatine, were isolated and characteriz

Alkaloids and coumarins from stem bark of Citrus grandis

Abstract An acetone extract of the stem bark of Citrus grandis. f. buntan afforded a new acridone alkaloid, buntanmine-A and a new coumarin, buntansin, together with six known acridone alkaloids and 10 known coumarins. Structures were elucidated by spectral methods and chemical transformations.