Polyhydroxylated alkaloids isolated from mulberry trees (Morusalba L.) and silkworms (Bombyx mori L.)

Design and Evaluation of Dihydroxytetrahydro-1H-pyrrolo[2,1-c]- [1,4]benzothiazines as Conformationally Restricted Transition-State Inhibitors of β-Ribosidases

[structure: see text] The preparation of three new chiral thiazines from ribose is described. Two of these are dihydroxytetrahydro-1H-pyrrolo[2,1-c][1,4]benzothiazines with iminopentitol substructures corresponding to the L-lyxo and D-ribo configurations. They were designed to present a favorable transition-state mimic for the inhibition of ribosidases. This new thiazine class opens the way to the development of new inhibitors to carbohydrate processing enzymes of therapeutic importance such as nucleoside hydrolases and purine nucleoside phosphorylases.

Study of the hypoglycaemic activity of Lepidium sativum L. aqueous extract in normal and diabetic rats

The hypoglycaemic effect of an aqueous extract of Lepidium sativum L. (LS) seeds was investigated in normal and streptozotocin (STZ)-induced diabetic rats. After a acute (single dose) or chronic (15 daily repeated administration) oral treatments, the aqueous LS extract (20 mg/kg) produced a significant decrease on blood glucose levels in STZ diabetic rats (p < 0.001); the blood glucose levels were normalised 2 weeks after daily repeated oral administration of aqueous LS extract (20 mg/kg) (p < 0.001). Significant reduction on blood glucose levels were noticed in normal rats after both acute (p < 0.01) and chronic treatment (p < 0.001). In addition, no changes were observed in basal plasma insulin concentrations after treatment either in normal or STZ diabetic rats indicating that the underlying mechanism of this pharmacological activity seems to be independent of insulin secretion. We conclude that the aqueous extract of LS exhibits a potent hypoglycaemic activity in rats without affecting basal plasma insulin concentrations.

Pachyelasides A-D, novel molluscicidal triterpene saponins from Pachyelasma tessmannii

This is the first report for secondary metabolites in an African medicinal plant, Pachyelasma tessmannii (Leguminosae). Four novel saponins, pachyelasides A-D, were isolated from the methanol extract of the root bark by using recycling HPLC. These compounds showed molluscicidal activity (LD(50) < or =8.0 mug/mL) against the South American snail, Biomphalaria glabratus. The structures were determined on the basis of extensive nuclear magnetic resonance spectroscopic and matrix-assisted laser desorption/ionization time-of-flight mass spectrometric studies.

Biological Properties of d- and l-1-Deoxyazasugars

L-Enantiomers of 1-deoxynojirimycin (DNJ), 1-deoxymannojirimycin (manno-DNJ), 1-deoxyallonojirimycin (allo-DNJ), 1-deoxyaltronojirimycin (altro-DNJ), 1-deoxygalactonojirimycin (galacto-DNJ), 1-deoxygulonojirimycin (gulo-DNJ), and 1-deoxyidonojirimycin (ido-DNJ) were prepared according to prior methods for the d-enantiomers. These enantiospecific syntheses established unambiguously the absolute configuration of naturally occurring DNJ, manno-DNJ, allo-DNJ, altro-DNJ, and gulo-DNJ. Although d-DNJ and d-galacto-DNJ are known to be powerful competitive inhibitors of alpha-glucosidase and alpha-galactosidase, respectively, with K(i) values in the nM range, l-DNJ and l-galacto-DNJ were noncompetitive inhibitors of alpha-glucosidase and alpha-galactosidase, respectively, with K(i) values in the muM range. However, the azasugar mimicking the structure of the terminal sugar moiety of the natural substrate is not always an inhibitor of the glycosidase responsible for the hydrolysis. d-manno-DNJ is known as a much better inhibitor of alpha-l-fucosidase than alpha-mannosidase, while l-allo-DNJ was a better inhibitor than d-manno-DNJ of alpha-mannosidase. l-galacto-DNJ can be regarded as the 6-hydroxylated derivative of deoxyfuconojirimycin (DFJ), which is a powerful inhibitor of alpha-l-fucosidase with a K(i) value in the nM range. However, this replacement of the methyl group in DFJ by a hydroxymethyl group reduced its affinity by about 50-fold. This suggests that there is a hydrophobic region in or around the active site of alpha-l-fucosidase. It has been found that inhibitors of human lysosomal glycosidases have therapeutic potential for the corresponding lysosomal storage diseases (Nat. Med. 1999, 5, 112; Proc. Natl. Acad. Sci. USA, 2002, 99, 15428). Inhibition of human lysosomal glycosidases by the 1-deoxyazasugars synthesized was investigated. d-galacto-DNJ is a potent inhibitor of lysosomal alpha-galactosidase (IC(50) = 90 nM) and is now being evaluated preclinically for its potential use in Fabry disease, while d-DNJ inhibiting alpha-glucosidase (IC(50) = 40 nM) potently does not appear to become a potential therapeutic agent because of additional inhibitory activity toward glycoprotein processing alpha-glucosidases. On the other hand, although l-allo-DNJ is a moderate inhibitor of alpha-mannosidase (IC(50) = 64 microM), it may become a key compound for the drug design of potential therapeutic agents for alpha-mannosidosis.

Natural medicines used in the traditional Chinese medical system for therapy of diabetes mellitus

The rapidly increasing diabetes mellitus is becoming a serious threat to mankind health in all parts of the world. The control and treatment of diabetes and its complications mainly depend on the chemical or biochemical agents, but the fact is that it has never been reported that someone had recovered totally from diabetes. With the distinctive traditional medical opinions and natural medicines mainly originated in herbs, the traditional Chinese medicine performed a good clinical practice and is showing a bright future in the therapy of diabetes mellitus and its complications. Based on a large number of chemical and pharmacological research work, numerous bioactive compounds have been found in Chinese medicinal plants for diabetes. The present paper reviews 86 natural medicines with regards to their origin, anti-diabetic active principles and/or pharmacological test results, which are commonly used in the traditional Chinese medical system and have demonstrated experimental or/and clinical anti-diabetic effectiveness. Among these natural medicines, 82 originate from plants and 4 from animals or insects, which covers 45 families. It is strongly significant to pay close attention to traditional Chinese medical therapeutics and natural medicines for treatment of diabetes mellitus and its complications.

Determination of 1-deoxynojirimycin in mulberry leaves using hydrophilic interaction chromatography with evaporative light scattering detection

A simple and rapid method for determining 1-deoxynojirimycin (DNJ), a potent glucosidase inihibitor present in mulberry leaves (Morus alba and Morus bombysis), by high-performance liquid chromatography coupled to an evaporative light scattering detector (ELSD) has been developed. DNJ was separated from an extract of mulberry leaves on a TSKgel Amide-80 column, which is a representative column for hydrophilic interaction chromatography. During postcolumn detection, DNJ was detected by ELSD and concurrently identified by mass spectrometry. The detection limit was 100 ng. This method is sufficiently sensitive for determining DNJ in mulberry leaves and other related products.

Antioxidant role of mulberry (Morus indica L. cv. Anantha) leaves in streptozotocin-diabetic rats

BACKGROUND

The antihyperglycemic and antioxidant role of mulberry (Morus indica L.) leaves were investigated.

METHODS

Streptozotocin (STZ)-induced diabetic male Wistar rats were used as experimental models; one group was given 25% dry mulberry leaf powder mixed with the standard diet and another group was given standard diet for a period of 8 weeks. The antihyperglycemic and antioxidant role of mulberry was assessed by determining its effect on blood glucose, lipid peroxidation, reduced glutathione (GSH) concentrations and on the activity of glucose-6-phosphate dehydrogenase (G6PDH) and various antioxidant enzymes in erythrocytes and compared with that of controls.

RESULTS

Mulberry-treated diabetic rats showed a significant decrease in fasting blood glucose concentrations indicating a good glycemic control. Increased lipid peroxidation and the activity of catalase (CAT) in erythrocytes observed in diabetic controls were significantly decreased by mulberry leaves (48% and 33%, respectively). Decreased GSH concentrations and the activity of glucose-6-phosphate dehydrogenase and antioxidant enzymes viz., glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST) and superoxide dismutase (SOD) observed in uncontrolled diabetes were improved (52%, 69%, 151%, 95%, 24% and 106%) by mulberry treatment very efficiently.

CONCLUSION

Mulberry leaves possess antihyperglycemic and antioxidant properties.

Determination of 1-deoxynojirimycin in Morus alba L. leaves by derivatization with 9-fluorenylmethyl chloroformate followed by reversed-phase high-performance liquid chromatography

A rapid and reliable method suitable for assays of a large number of Morus alba leaves for 1-deoxynojirimycin (DNJ) has been developed. DNJ in 0.1 g of freeze-dried leaves was double-extracted in 10 mL of aqueous 0.05 M HCl by vortexing for 15 s at room temperature, derivatized with 9-fluorenylmethyl chloroformate (FMOC-Cl), and analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) equipped with a fluorescence detector. The double extraction recovered > 99% of extractable DNJ from the leaves. Stabilization of FMOC-derivatized DNJ (DNJ-FMOC) was achieved by diluting the reactant with aqueous acetic acid after derivatization. DNJ-FMOC was stable for at least 16 days under acidic conditions at room temperature (24 degrees C). Linearity ranged between 0.3 and 30 microg mL(-1). The intra- and inter-day precision for DNJ-spiked biological samples was between 0.6 and 1.8% and between 3.7 and 4.5%, respectively.

Inhibitory effect of aqueous extract from the gall of Rhus chinensis on alpha-glucosidase activity and postprandial blood glucose

The present study examined the inhibitory effect of aqueous extract from the gall of Rhus chinensis (AEGRC) on alpha-glucosidase activity, an enzyme responsible for digestion of carbohydrate to monosaccharides in the process of intestinal absorption. AEGRC inhibited Bacillus alpha-glucosidase acitvity with an IC(50) of 0.9 micro g/ml. Its inhibition on alpha-glucosidase was determined to be noncompetitive and reversible when the enzyme-substrate mixture was simultaneously treated with AEGRC as an inhibitor. In addition, when it was orally administered to rats with sucrose (2g/kg), AEGRC (250-1000mg/kg) significantly suppressed the increase of blood glucose levels after sucrose loading in a dose dependent manner. These results suggest that AEGRC might exert anti-diabetic effect by suppressing carbohydrate absorption from intestine, and thereby reducing the postprandial increase of blood glucose.

Analysis of tropane and related alkaloids

The current methods for tropane alkaloid chromatographic separation and determination are summarised. The alkaloids included are: the medicinally applied tropic acid esters hyoscyamine and scopolamine and their derivatives, cocaine and derivatives, the metabolites and degradation products of these compounds occurring in plant material, calystegines as nortropane alkaloids, anatoxins as homonortropane alkaloids, pelletierines and pseudopelletierines as alkaloids with isomeric structures. Developments in GC, HPLC, CE and TLC are presented and the advantages of each method for plant analysis are discussed. A summary for each chromatographic method lists the instrumentation and parameters applied for tropane alkaloids.