Antidiabetic and antioxidant activities of major flavonoids of Cynanchum acutum L. (Asclepiadaceae) growing in Egypt.

Seven flavonoids were isolated from the butanol fraction of the methanolic extract of the aerial parts of Cynanchum acutum L. (Asclepiadaceae). All of which have been isolated for the first time from the genus Cynanchum. Their structures were established as quercetin 3-O-beta-galacturonopyranoside (1), quercetin 7-O-beta-glucopyranoside (2), tamarixtin 3-O-beta-galacturonopyranoside (3), kaempferol 3-O-beta-galacturonopyranoside (4), 8-hydroxyquercetin 3-O-beta-galactopyranoside (5), tamarixtin 3-O-alpha-rhamnopyranoside (6), and tamarixtin 7-O-alpha-arabinopyranoside (7) on the basis of their chromatographic properties, chemical and spectroscopic data. The major isolated flavonoids 1, 2 and 3 were found to exhibit significant antioxidant and antidiabetic activities (by measuring blood glucose and insulin levels). This is the first report about the antioxidant and antidiabetic activities of compounds 1-3.

An acylated flavonol glycoside and hydrolysable tannins from Callistemon lanceolatus flowers and leaves.

INTRODUCTION: Callistemon lanceolatus DC. (Myrtaceae) is a plant rich in polyphenols, and is used as anticough, antibronchitis and insecticide in folk medicine. Because of the biological importance of plant polyphenols, particularly tannins, a phytochemical study was of interest to investigate the constitutive poyphenols in the extracts of flowers and leaves. OBJECTIVE: To avoid time-consuming methodology for isolation of a complex mixture of known metabolites, HPLC-ESI/MS was employed for fast picking up of the new compounds followed by identification of the structures with UV and one- and two-dimensional NMR. METHODOLOGY: Flowers and leaves were separately extracted with hot aqueous methanol under reflux (70 degrees C). Pre-isolation of the total extracts was achieved through column chromatographic fractionation on polyamide with water-methanol for gradient elution. The main fractions were purified using repeated column chromatography on cellulose and/or Sephadex LH-20 with suitable eluents. HPLC-ESI/MS analyses were carried out in the single ion monitoring (SIM) and negative ion modes. The pure compounds in methanol-water (1:1) were analysed by direct infusion ESI/MS. Final structure elucidation was obtained by one- and two-dimensional NMR. RESULTS: Two new metabolites namely quercetin 3-O-beta-D-glucuronopyranoside n-butyl ester (1) and n-butylgallate 4-O-(2',6'-di-O-galloyl)-beta-D-glucopyranoside (4) along with nine known ones were identified from the aqueous methanol extracts of flowers and leaves. CONCLUSION: The study has shown that Callistemon lanceolatus is rich in polyphenols. HPLC-ESI/MS may be used, in negative ion mode, as an efficient and rapid analytical tool for investigating complex plant extracts.

Isoflavonoid glycosides and rotenoids from Pongamia pinnata leaves.

Chromatographic separation of a 70% aqueous methanol extract (AME) of Pongamia pinnata (Linn.) Pierre (Leguminosae) leaves has led to the isolation of two new isoflavonoid diglycosides, 4'-O-methyl-genistein 7-O-beta-D-rutinoside (2) and 2',5'-dimethoxy-genistein 7-O-beta-D-apiofuranosyl-(1"'-->6")-O-beta-D-glucopyranoside (6), and a new rotenoid, 12a-hydroxy-alpha-toxicarol (5), together with nine known metabolites, vecinin-2 (1), kaempferol 3-O-beta-D-rutinoside (3), rutin (4), vitexin (7), isoquercitrin (8), kaempferol 3-O-beta-D-glucopyranoside (9), 11,12a-dihydroxy-munduserone (10), kaempferol (11), and quercetin (12). Their structures were elucidated on the basis of chemical and spectroscopic analyses.

Anticancer and antioxidant tannins from Pimenta dioica leaves.

Two galloylglucosides, 6-hydroxy-eugenol 4-O-(6'-O-galloyl)-beta-D-4C1-glucopyranoside (4) and 3-(4-hydroxy-3-methoxyphenyl)-propane-1,2-diol-2-O-(2',6'-di-O-galloyl)-beta-D -4C1-glucopyranoside (7), and two C-glycosidic tannins, vascalaginone (10) and grandininol (14), together with fourteen known metabolites, gallic acid (1), methyl gallate (2), nilocitin (3), 1-O-galloyl-4,6-(S)-hexahydroxydiphenoyl-(alpha/beta)-D-glucopyranose (5), 4,6-(S)-hexahydroxydiphenoyl-(alpha/beta)-D-glucopyranose (6), 3,4,6-valoneoyl-(alpha/beta)-D-glucopyranose (8), pedunculagin (9), casuariin (11), castalagin (12), vascalagin (13), casuarinin (15), grandinin (16), methyl-flavogallonate (17) and ellagic acid (18), were identified from the leaves of Pimenta dioica (Merr.) L. (Myrtaceae) on the basis of their chemical and physicochemical analysis (UV, HRESI-MS, 1D and 2D NMR). It was found that 9 is the most cytotoxic compound against solid tumour cancer cells, the most potent scavenger against the artificial radical DPPH and physiological radicals including ROO*, OH*, and O2-*, and strongly inhibited the NO generation and induced the proliferation of T-lymphocytes and macrophages. On the other hand, 3 was the strongest NO inhibitor and 16 the highest stimulator for the proliferation of T-lymphocytes, while 10 was the most active inducer of macrophage proliferation.

Phytochemical constituents and hepatoprotective activity of Viburnum tinus.

From the leaves of Viburnum tinus L. (Adoxaceae) two acylated iridoid glucosides (viburtinoside A and B), a coumarin diglucoside scopoletin 7-O-beta-D-sophoroside and a natural occurred dinicotinic acid ester 2,6-di-C-methyl-nicotinic acid 3,5-diethyl ester were isolated. In addition to these, 10 known compounds were isolated, namely two bidesmosidic saponins, a hexamethoxy-flavone and five flavonol glycosides, as well as suspensolide A and oleanolic acid were isolated for the first time in this genus and species, respectively. The structures were determined mainly by spectroscopic methods (UV, IR, ESI-MS, 1H-, 13C NMR and DEPT). Toxicity of the investigated extract was determined (LD50=500 mg/kg). CCl4-induced hepatotoxicity has been evaluated in terms of the determination of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lipid peroxide and nitric oxide levels in serum and compared using adult male rats weighing 150-180 g. Their highly elevated levels were significantly reduced by treatment with the investigated aqueous methanol extract in dose-dependent manner.

Pharmacologically active ellagitannins from Terminalia myriocarpa.

A new ellagitannin, methyl (S)-flavogallonate (14) along with fourteen known compounds, gallic acid, methyl gallate, ethyl gallate, 2,3-di-O-[( S)-4,5,6,4',5',6'-hexahydroxybiphenyl-2,2'-diyldicarbonyl]-(alpha/beta)-D-glucopyranose (4), vitexin, isovitexin, orientin, iso-orientin, kaempferol 3-O-beta-D-rutinoside, rutin, neosaponarin, ellagic acid, flavogallonic acid (13), and (alpha/beta)-punicalagin (15) have been isolated from the leaves of Terminalia myriocarpa Heurck. Protective effect of the major and structurally related compounds 4, 13, 15 and the new compound 14 against CCl 4 -induced hepatotoxicity has been evaluated and compared, using adult male rats weighing 200-250 g. Serum levels of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), lipid peroxide and nitric oxide production were significantly increased by administration of CCl 4 to rats and then reduced significantly only by treatment with compounds 4, 14 and 15 in a dose-dependent manner. Comparison of the protective properties of these compounds showed that compound 14 is more potent than compound 15 than 4 and that compound 13 has a non-significant effect at the used two dose levels.