A New Dimeric Carbazole Alkaloid from Glycosmis stenocarpa Roots

Abstract

The genus Glycosmis, family Rutaceae, is a rich source of alkaloids, including those of the quinolone, quinazoline, furoquinoline, acridone, sulphur-containing amides and carbazole types.1,2) Carbazole alkaloids were isolated from the seeds 3) and the roots 4,5) of G. pentaphylla, from the bark of G. mauritiana 6) and G. rupestris, 7) and from the roots of G. arborea. 8) Carbazole alkaloids have also been found in other Rutaceous genera, e.g., Micromelum, Murraya, and Clausena. From two genera, Murraya and Clausena, nearly four fifths of the natural carbazole alkaloids have been isolated.9,10) In a continuing search for bioactive natural products from Vietnamese plants, a number of plants, including species Glycosmis stenocarpa (DRAKE) TAN., have been screened for cytotoxic, antifungal, and antibacterial activities.11,12) G. stenocarpa, local name "com ruou trai hep," is a small shrub, 0.75-1 m high. It is an endemic plant, found in some provinces in north Vietnam.13) This paper reports the isolation and structural elucidation of a new dimeric pyranocarbazole alkaloid, named bisisomahanine (1), and two known monomeric carbazole alkaloids, viz. murrayafoline-A (2) 14) and murrayanine (3), 15) from the roots of G. stenocarpa. Results and DiscussionBisisomahanine (1) was obtained as a pale ivory powder, mp 130-140°C, [a] D 20 Ϫ13.1°. The UV spectrum showed the typical absorbances at 209, 224, and 245 nm, closely similar to those of 2 and 3, and indicative of the carbazole skeleton in 1. Furthermore, it exhibited absorbances at 298 (sharp, strong) and 335 nm (broad, weak), typical of an angular pyranocarbazole unit as described for isomahanine (4). (Table 1) and the peak at m/z 83 in the EI-MS spectrum were assignable to the isohexenyl side chain.16,17) The assignments of carbons at positions C-1Ј and C-2Ј of alkaloid 1 are different than those reported for isomahanine (4), 16) and were confirmed by data from HMQC and HMBC experiments ( Table 1). The HMQC spectrum of 1 showed the direct .1 (C-3Ј), and 22.7 (C-2Ј). The 1 H-1 H COSY and NOESY spectra of 1 also confirmed the above assignment of the isohexenyl side chain (Fig. 1).In the downfield region of the 1 H-NMR spectrum, two broad singlets at d 7.51 and 5.14 were assigned to an NH and a phenolic hydroxyl group, respectively; this was supported by the IR bands at 3470 and 3362 cm Ϫ1, and the fact that no carbons were attached to these proton signals, as shown by the HMQC spectrum. There were two isolated pairs of orthocoupled protons: the first pair at d 6.73 (H-5) and 7.71 (H-6), and the second at d 6.43 (H-1) and 5.54 (H-2). The COSY spectrum confirmed the two separate spin systems. The NMR spectral data of the latter pair were similar to those in some Murraya alkaloids such as isomahanine (4) and mahanine (5), 16) murrayamine C (7), 18) and pyrayafoline-D (6) (assigned the same structure as 4 by Ito et al.), 17) indicating the presence of a pyran ring double bond in the pyranocarbazoletype skeleton of 1.The position of fusion between the pyrano and carbazole ...

Alkaloids from the Stems of Glycosmis pentaphylla

“…3.96 (s) 56.9 (q) C ( 3 ') genus. Bisisomahanine isolated from G. stenocarpa represented the first dimeric prenylated pyranocarbazole alkaloid with a 1,1'-linkage [16]. In the present study, compounds 2 and 3 which present a 1,1'-linkage between two carbazole moieties, were isolated from G. pentaphylla for the first time.…”

Anti-Inflammatory Effect of 3-Methylcarbazoles on RAW 264.7 Cells Stimulated with LPS, Polyinosinic-Polycytidylic Acid and Pam3CSK

“…Since the first report of a carbazole alkaloid, murrayanine, from the stem bark of Murraya koenigii [15], a number of carbazole alkaloids have been isolated from this plant [16][17][18][19][20] and other plants [13,21]. Although there are many carbazole alkaloid derivatives that have special ability to scavenge reactive oxygen species-free radicals, such as hydroxyl radicals, superoxide radicals, or hypochlorous acid, and to influence processes involving free-radical injury [22,23], they have also been found to inhibit lipid peroxidation and to possess vasorelaxant [24][25][26] and anti-inflammatory/antioxidant activity [20].…”

Synthesis of Tetranuclear Palladium(II) Complexes and Their Catalytic Activity for Cross‐Coupling Reactions

“…Bisisomahanine (8), ah omocoupling product of pyrayafoline D, was isolatedi n 2004 by Cuong et al from the roots of Glycosmis stenocarpa and reported to be optically active (½a 20 D = À13.1, c = 0.25, CHCl 3 ). [68] However,t he authors did not assign the absolute configuration. Treatment of pyrayafoline C( 23)a nd D( 24)w ith di-tert-butyl peroxide afforded the corresponding dimers 7 and 8 in 85 %a nd 64 %y ield, respectively ( Table 3).…”