.ALPHA.-Glucosidase Inhibitory Constituents from Cuscuta reflexa.

Abstract

The genus Cuscuta belonging to the family Convolvulaceae, comprises three species. All of these are leafless, twining parasites with slender yellowish stems, 1) distributed in tropical and temperate regions. Cuscuta reflexa ROXB. is a leafless parasitic climber which is commonly found in Karachi and other parts of Pakistan. This plant is depurative and purgative and is used in retention of wind and induration of liver while externally used against itches and skin diseases.2) Previously, long chain esters of the oleane series and sterol glycosides have been reported from this plant.3) The methanolic extract and its subsequent ethyl acetate fraction showed significant inhibition against a-glucosidase, while against other enzymes (thrombin, b-glucuronidase) gave negative results. a-Glucosidase is a membrane bound enzyme at the epithelium of the small intestine. Inhibition of this enzyme prolongs the absorption time of glucose in the blood after a meal. 4) Thus, post prandial hyperglycaemia can be decreased and in this way non-insulin dependent diabetes (NIDDM) can be managed. This prompted us to carry out further phytochemical studies on this plant. In this paper we describe the isolation and structural elucidation of two new compounds namely, 7Ј-(3Ј,4Ј-dihydroxyphenyl)-N-[(4-methoxyphenyl)ethyl]propenamide (4) and 7Ј-(4Ј-hydroxy,3Ј-methoxyphenyl)-N-[(4-butylphenyl)ethyl]propenamide (5) together with five known compounds, 6,7-dimethoxy-2H-1-benzopyran-2-one (1), (6) 8) and 2-(3-hydroxy-4-methoxyphenyl)-3,5-dihydroxy-7-O-b -D-glucopyranoside-4H-1-benzopyrane-4-one (7), 9) reported for the first time from this species. All of these compounds have been isolated from the hexane insoluble residue of the ethyl acetate fraction obtained from fractionation of the methanolic extract, followed by repeated column chromatography over silica gel, as described in the Experimental.Compound 4 was assigned the molecular formula C 18 H 19 NO 4 by high resolution (HR)-MS, which showed a [M] ϩ peak at m/z 313.1285 (Calcd 313.1292 ).10) The UV spectrum showed strong absorption maxima at l max 320, 290 and 225 nm, indicating a highly conjugated system.10) The MS of 4 displayed an ion peak at m/z 178 which was due to the loss of C 8 H 7 O 2 from the molecular ion. The ion at m/z 163 was assigned to the fragment C 9 H 7 O 3 . The fragment at m/z 136 corresponded to C 8 H 8 O 2 , resulting from the cleavage of the bond between (C-8Ј) and the carbonyl bond. This fragmentation pattern suggested that the two hydroxyl groups were in ring A.11) This was also confirmed by acetylation which gave the diacetate 4a. The 1 H-NMR spectrum of 4 showed a signal at d 3.78 due to a methoxyl group and further signals for methylene groups at d 2.66 (2H, t, Jϭ7.1 Hz) and d 3.39 (2H, t, Jϭ7.1 Hz). The two doublets at d 6.92 and 6.93 (d, 2H, Jϭ8.3 Hz) were assigned to H-2/H-6 and H-3/H-5 hydrogens. The presence of a disubstituted cinnamate group was confirmed by ABX-type signals at d 6.89 (d, Jϭ1.7 Hz,) 6.78 (d, Jϭ8.1 Hz,), 6.87 (dd, Jϭ8.1, 1.7 Hz) together ...

Characterization of phenolic compounds in the Chinese herbal drug Tu‐Si‐Zi by liquid chromatography coupled to electrospray ionization mass spectrometry

“…A characteristic cleavage of the tetrahydrofuran ring (pathway I) was proposed, and the observed fragments could provide important information on substitutions of the benzyl rings. Lignans of this type have been reported to be related to the tonic effects of Tu‐Si‐Zi, and their physiological activities should be further studied 26…”

6,7,8-Trimethoxycoumarin fromCryptocarya bracteolata

“…For the isolation and spectroscopic characterization of 6,7,8trimethoxycoumarin that has been isolated from other plants, see: Adesina et al (1997); Amaral et al (2001); Anis et al (1999Anis et al ( , 2002; Anjaneyulu & Murty (1981); Bohlmann et al (1981Bohlmann et al ( , 1985; Boulware & Stermitz (1981); Borges del Castillo et al (1987); Campbell (1996); Campbell et al (1986); Cheng et al (2005); Del Castillo et al (1984); Eshiett & Taylor (1968); Estevez-Braun et al (1995); Facundo et al (2002); Goh et al (1989Goh et al ( , 1990; Gonzalez et al (1972Gonzalez et al ( , 1975Gonzalez et al ( , 1977; Goren et al (1988); Hsiao & Chiang (1995); Iqbal et al (2003); Iossifova et al (1994); Ishi et al (1972); Ishii et al (1981Ishii et al ( , 1982; Ishikawa et al (1995); Laskaris et al (1995); Macleod & Rasmussen (1998); Mbwambo et al (1996); Oksuz (1990); Qi et al (2004); Ren et al (1991); Rios & Flores (1976); Sang et al (2005); Semple et al (1999); Shi et al (2005…”

Biological significance of essential oil ofZataria multifloraboiss

“…Enzyme Inhibition Activity The -glucocidase (type VI, sigma G6136) inhibition was observed spectrophotometrically at pH 6.8 and at 37 C using 0.7 mM p-nitrophenyl -D-glucopyranoside (PNP-G) as a substrate and 0.017 units/mL enzyme, in 50 mM sodium phosphate buffer containing 100 mM Nacl, with 0.3 mM 1-deoxynijirimycin used as positive control (IC 54 ¼ 0.3 mM) [12]. The increase in absorption at 400 nm due to the hydrolysis of PNP-G by -glucocidase was studied continuously with a spectrophotometer (Molecular Devices, Sunnyvale, CA) [13].…”