Two new lupane derivatives, 3beta,6alpha-dihydroxylup-20(29)-ene (1) and 6alpha-hydroxylup-20(29)-en-3beta-octadecanoate (2), have been isolated from the stems of Periploca aphylla, in addition to beta-sitosterol and lupeol. The structures of 1 and 2 were determined by spectral and chemical methods. Compound 1 showed strong inhibition of alpha-glucosidase type VI and a moderate antibacterial activity.

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 ...

No abstract