Acetylcholinesterase inhibitor from Anthocleista vogelii leaf extracts.

BACKGROUND: Anthocleista vogelii (Planch) is used in folk medicine in conditions related to inflammation and oxidative stress. This suggests that some of its constituents could possess ability to reduce oxidative damage to cells and ameliorate inflammatory conditions which are two prominent features in the brain of a person suffering from Alzheimer's disease. AIM OF STUDY: The leaf extracts were investigated for their bioactive constituents in our quest for novel compounds for the management of Alzheimer's disease. MATERIALS AND METHODS: Anthocleista vogelii crude leaf extract obtained from 80% methanol was successively partitioned with n-hexane, dichloromethane (DCM), ethyl acetate (EtOAc) and n-butanol. This gave four solvent fractions of the crude extract. These fractions and isolated compound were subjected to acetylcholinesterase (AChE) inhibitory activity test using the microplate assay method. The structure of the isolated compound was determined using spectroscopic methods (1D and 2D NMR, and MS). RESULTS: The results of the acetylcholinesterase inhibitory assay revealed that n-BuOH and ethyl acetate fractions had the best activity with IC50 of 564.58 and 727.63 µg/mL respectively. Activity directed fractionation of each of these fractions led to the isolation of the same compound identified as a C-glucosylflavone; isovitexin-7-O-methyl ether (swertisin). This rare C-glucosylflavone co-exist as two rotamers and exhibited duplication of NMR signals. It is reported from this plant for the first time. Swertisin displayed better acetylcholinesterase inhibitory activity with IC50 of 32.09 µg/mL than physostigmine (eserine) with IC50 of 56.09 µg/mL used as a standard. CONCLUSIONS: This study reports isolation and characterization of a rare C-glycosylflavone; isovitexin-7-O-methyl ether (swertisin). Isolated compound exhibited duplication of NMR signals and better acetylcholinesterase inhibitory activity than eserine used as a standard. The activity exhibited by this compound suggests that it could be useful in the management of Alzheimer's disease.

Vangueria infausta root bark: in vivo and in vitro antiplasmodial activity.

Vangueria infausta burch subsp. infausta (Rubiaceae) produces fruits eaten by humans and animals. The leaf, fruit, stem bark and root bark are used as a remedy for many ailments and the roots are used to treat malaria. In this study, concentrations of fractions of the V. infausta root bark extract that produce 50% inhibition (IC50) are determined using the ability of the extract to inhibit the uptake of [G3H]-hypoxanthine by P. falciparum cultured in vitro. The root bark extract showed antimalarial activity against Plasmodium berghei in mice. It gave a parasite suppression of 73.5% in early infection and a repository effect of 88.7%. One fraction obtained from a chloroform extract gave an IC50 value of 3.8 +/- 1.5 microg/mL and 4.5 +/- 2.3 microg/mL against D6 and W2 strains of P. falciparum, respectively, and another from the butanol extract gave an IC50 value of 3.9 +/- 0.3 microg/mL against the D6 strain. Chloroquine had an IC50 value of 0.016 microg/mL and 0.029 microg/mL against D6 and W2 strains, respectively. The plant showed the presence of flavonoids, coumarins, tannins, terpenoids, anthraquinones and saponins.

A new stilbene glycoside from Elephantorrhiza goetzei.

A new stilbene glycoside, 5-methoxy-(E)-resveratrol 3-O-rutinoside (1) was isolated from the root bark of Elephantorrhiza goetzei, along with known compounds, namely gallic acid, (E)-resveratrol, (+/-)-catechin, (+/-)-gallocatechin and oleanene triterpenoids. The combined ethyl acetate-methanol extract exhibited high lethality against brine shrimp larvae (LC(50) 10.8 ppm) compared to the isolates, some of which were not active.

Isoflavone glycosides from the root wood of Erythrina latissima.

The molecular structures of 3 isoflavone glycosides isolated from the root wood of Erythrina latissima were established as 4'-hydroxyisoflavone-7-O-beta-D-glucopyranoside (compound 1); 4'-hydroxyisoflavone-7-O-alpha-L-rhamnosyl (1-->6)-beta-D-glucopyranoside (compound 2); and a new compound 4', 8-dimethoxy isoflavone-7-O-alpha-L-rhamnosyl (1-->6) glucopyranoside (8-O-methylretusin-7-O-alpha-L-rhamnosyl (1-6)-beta-D-glucopyranoside) (compound 3).

Flavonoids from the stem bark of Bolusanthus speciosus.

Three flavonoids (bolusanthols A-C), viz an isoflavan and two prenylated isoflavanones, were isolated from the stem bark of Bolusanthus speciosus in addition to four known flavonoids, 5,7,3'-trihydroxy-4'-methoxy-5'-methoxy-gamma,gamma-dimethylallylisoflavanone, 5,7,2'-trihydroxy-4'-methoxy-6,5'-di(gamma,gamma)-dimethylallyl)isoflavanone, 3,5,7,3',4'-pentahydroxy-6-gamma,gamma-dimethylallylflavone and 5,7,2',4'-tetrahydroxy-8,3'-di(gamma,gamma-dimethylallyl)-isoflavanone. The structure of the new compounds were determined to be 4,2',3',4'-tetrahydroxy-6,7-methylenedioxyisoflavan (bolusanthol A), 5,7,3',4'-tetrahydroxy-5'-gamma,gamma-dimethylallylisoflavanone (bolusanthol B), and 5,7,4'-trihydroxy-6,3'-di(gamma,gamma-dimethylallyl)isoflavanone (bolusanthol C) by spectroscopic methods.

A new isoflavanone from the stem bark of Erythrina latissima.

Two isoflavonoids--including the new compound 5,7-dihydroxy-2',4',5'-trimethoxyisoflavanone (1)--six flavanones and a feruloyl ester were isolated from the stem bark of Erythrina latissima.

Two novel glucodienoid alkaloids from Erythrina latissima seeds.

The structures of two novel glycodienoid alkaloids isolated from Erythrina latissima seeds have been established as (+)-16beta-D-glucoerysopine (1) and (+)-15beta-D-glucoerysopine (2). NOE measurements established that 1 and 2 are positional isomers. Their structures were elucidated from their 1D and 2D homonuclear and heteronuclear NMR spectroscopic data. In addition, seven known tetracyclic dienoid alkaloids were isolated and identified as (+)-erysovine, (+)-erysodine, (+)-erysotrine, (+)-erythraline, (+)-beta-D-glucoerysodine, (+)-8-oxoerythraline, and (+)-erysotramidine.

Phenolic and antibacterial constituents of Vahlia capensis.

The n-butanol fraction of Vahlia capensis yielded kaempferol, quercetin, afzelin, astragalin, quercitrin, isoquercitrin, rutin, gallic acid, chiro-inositol, dulcitol, and a novel biflavonoid, VC-15B (vahlia biflavone). The compounds were identified using 1D and 2D NMR techniques and FABMS. Vahlia biflavone and gallic acid were isolated, using bioassay-guided procedure and identified as the antibacterial components. Both compounds showed activity against Gram positive Staphylococcus aureus and Bacillus subtilis. Vahlia biflavone gave MIC values of 15.3 micrograms/ml and 30.6 micrograms/ml against S. aureus and B. subtilis, respectively while gallic acid gave a value of 71.3 micrograms/ml for both organisms.

Bufadienolides and other constituents of Urginea sanguinea.

Fresh bulbs of Urginea sanguinea yielded stigmasterol, phloroglucinol, phloroglucinol 1-beta-D-glucopyranoside (phlorin), scillaren A, a novel compound 5 alpha-4,5-dihydroscillaren A (1), salicylic acid, and 3-hydroxy-4-methylbenzoic acid. The latter two showed weak antibacterial activity. The compounds were identified using spectroscopic techniques such as 1D and 2D NMR, EI-MS and FAB-MS.