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

Mulberry 1-deoxynojirimycin pleiotropically inhibits glucose-stimulated vascular smooth muscle cell migration by activation of AMPK/RhoB and down-regulation of FAK

Mulberry 1-deoxynojirimycin (DNJ), an inhibitor of α-glucosidase, has been reported to help prevent diabetes mellitus and suppress lipid accumulation. The aim of this study was to determine whether mulberry DNJ has pleiotropic effects on the development of atherosclerosis. The mechanisms by which mulberry DNJ might inhibit migration of A7r5 vascular smooth muscle cells (VSMCs) under hyperglycemic conditions mimicking diabetes were investigated. The antimigratory effects of DNJ on VSMCs were assessed by Western blot analysis of migration-related proteins and by electric cell-substrate impedance sensing (ECIS) and visualization of F-actin cytoskeleton. Two pathways of DNJ-mediated inhibition of VSMC migration were identified. The first involved AMPK activation to inhibit fatty acid synthase (FASN) and Akt activity and then RhoB activation to inhibit nuclear factor-κB (NF-κB) and matrix metalloproteinase-2 (MMP) activity. The second involved inhibition of focal adhesion kinase (FAK), Ras, and RhoA activity leading to inhibition of F-actin activity.

The effect of polyhydroxylated alkaloids on maltase-glucoamylase

One of the most important carbohydrate-splitting enzymes is themaltase-glucoamylase which catalyzes the hydrolysis of alpha-glucosidic linkages. Maltase-glucoamylase inhibitors during the last few years have aroused medical interests in the treatment of diabetes. They contribute to a better understanding of the mechanism of maltase-glucoamylase. At present there are many different classes of maltase-glucoamylase inhibitors. This paper focuses on alkaloidal inhibitors of maltase-glucoamylase and structure-activity relationship (SAR) studies between them in order to discover some drugs with better efficiency and lower toxicity for treating diabetes.

The role of biocatalysis in the asymmetric synthesis of alkaloids

Alkaloids are not only one of the most intensively studied classes of natural products, their wide spectrum of pharmacological activities also makes them indispensable drug ingredients in both traditional and modern medicine. Among the methods for their production, biotechnological approaches are gaining importance, and biocatalysis has emerged as an essential tool in this context. A number of chemo-enzymatic strategies for alkaloid synthesis have been developed over the years, in which the biotransformations nowadays take an increasingly 'central' role. This review summarises different applications of biocatalysis in the asymmetric synthesis of alkaloids and discusses how recent developments and novel enzymes render innovative and efficient chemo-enzymatic production routes possible.

Segmental duplications in the silkworm genome

Background

Segmental duplications (SDs) or low-copy repeats play important roles in both gene and genome evolution. SDs have been extensively investigated in many organisms, however, there is no information about SDs in the silkworm, Bombyx mori.

Result

In this study, we identified and annotated the SDs in the silkworm genome. Our results suggested that SDs constitute ~1.4% of the silkworm genome sequence (≥1 kb in length and ≥90% in the identity of sequence); the number is similar to that in Drosophila melanogaster but smaller than mammalian organisms. Almost half (42%) of the SD sequences are not assigned to chromosomes, indicating that the SDs are challenges for the assembling of genome sequences. We also provided experimental validation of large duplications using qPCR. The analysis of SD content indicated that the genes related to immunity, detoxification, reproduction, and environmental signal recognition are significantly enriched in the silkworm SDs.

Conclusion

Our results suggested that segmental duplications have been problematic for sequencing and assembling of the silkworm genome. SDs may have important biological significances in immunity, detoxification, reproduction, and environmental signal recognition in the silkworm. This study provides insight into the evolution of the silkworm genome and an invaluable resource for insect genomics research.

Antidiabetic and antioxidant effects and phytochemicals of mulberry fruit (Morus alba L.) polyphenol enhanced extract

The antidiabetic and antioxidant activities of the ethyl acetate-soluble extract (MFE) of mulberry fruit (Morus alba L.) were investigated. In vitro, MFE showed potent α-glucosidase inhibitory activity and radical-scavenging activities against DPPH and superoxide anion radicals. In vivo, MFE could significantly decrease fasting blood glucose (FBG) and glycosylated serum protein (GSP), and increase antioxidant enzymatic activities (SOD, CAT, GSH-Px) in streptozotocin (STZ)-induced diabetic mice. Bioactivity-guided fractionation of the MFE led to the isolation of 25 phenolic compounds, and their structures were identified on the basis of MS and NMR data. All the 25 compounds were isolated from mulberry fruit for the first time. Also, the α-glucosidase inhibitory activity and antioxidant activity of the phenolics were evaluated. Potent α-glucosidase inhibitory and radical-scavenging activities of these phenolics suggested that they may be partially responsible for the antidiabetic and antioxidant activities of mulberry fruit.

Silkworm (Bombyx mori L.) reduces vasopressin expression in the hypothalamus of streptozotocin-induced diabetic mice

BACKGROUND

Hyperglycemia plays an important role in the development and progression of diabetic neuropathy, with which the expression of vasopressin is associated. This study was designed to investigate the effect of silkworm on the expression of vasopressin, a hormone synthesized in hypothalamic area, in the paraventricular (PVN) and supraoptic nucleus (SON) of hypothalamus in streptozotocin (STZ)-induced diabetic mice.

METHODS

Vasopressin-positive neurons in the PVN and SON of STZ-induced diabetic mice were identified by immunohistochemistry. Blood glucose levels were measured by One Touch Basic glucose measurement system. Intraperitoneal glucose tolerance (IPGT) tests were performed on overnight fasted mice.

RESULTS

STZ-induced diabetic mice fed with 0.4% silkworm group resulted in significantly decreased expression of vasopressin-positive neurons (107.8 +/- 5.4 in PVN and 140.8 +/- 8.5 in SON, p<0.05). In addition, blood glucose levels increased significantly in STZ-induced diabetic group (p<0.05). In contrast, STZ-induced mice fed with 0.4% silkworm group showed significantly decreased blood glucose level (p<0.05.

CONCLUSION

These observations may provide a scientific foundation for the increasingly used silkworm powder as an adjunct in the treatment of diabetes mellitus, especially diabetic neuropathy.

New methodologies for the extraction and fractionation of bioactive carbohydrates from mulberry (Morus alba) leaves

Pressurized liquid extraction (PLE) was applied for the first time to extract bioactive low molecular weight carbohydrates (iminosugars and inositols) from mulberry ( Morus alba ) leaves. Under optimized conditions, PLE provided a similar yield to the conventional process used to extract these bioactives, but in less time (5 vs 90 min). To remove carbohydrates that interfere with the bioactivity of iminosugars from PLE extracts, two fractionation treatments were evaluated: yeast ( Saccharomyces cerevisiae ) incubation and cation-exchange chromatography (CEC). Both methods allowed complete removal of major soluble carbohydrates (fructose, glucose, galactose, and sucrose), without affecting the content of mulberry bioactives. As an advantage over CEC, the yeast treatment preserves bioactive inositols, and it is an affordable methodology that employs food grade solvents. This work found PLE followed by yeast treatment to be an easily scalable and automatable procedure that can be implemented in the food industry.

Molecular cloning and characterization of the α-glucosidase II from Bombyx mori and Spodoptera frugiperda

The α-glucosidase II (GII) is a heterodimer of α- and β-subunits and important for N-glycosylation processing and quality control of nascent glycoproteins. Although high concentration of α-glucosidase inhibitors from mulberry leaves accumulate in silkworms (Bombyx mori) by feeding, silkworm does not show any toxic symptom against these inhibitors and N-glycosylation of recombinant proteins is not affected. We, therefore, hypothesized that silkworm GII is not sensitive to the α-glucosidase inhibitors from mulberry leaves. However, the genes for B. mori GII subunits have not yet been identified, and the protein has not been characterized. Therefore, we isolated the B. mori GII α- and β-subunit genes and the GII α-subunit gene of Spodoptera frugiperda, which does not feed on mulberry leaves. We used a baculovirus expression system to produce the recombinant GII subunits and identified their enzyme characteristics. The recombinant GII α-subunits of B. mori and S. frugiperda hydrolyzed p-nitrophenyl α-d-glucopyranoside (pNP-αGlc) but were inactive toward N-glycan. Although the B. mori GII β-subunit was not required for the hydrolysis of pNP-αGlc, a B. mori GII complex of the α- and β-subunits was required for N-glycan cleavage. As hypothesized, the B. mori GII α-subunit protein was less sensitive to α-glucosidase inhibitors than was the S. frugiperda GII α-subunit protein. Our observations suggest that the low sensitivity of GII contributes to the ability of B. mori to evade the toxic effect of α-glucosidase inhibitors from mulberry leaves.

Mulberry leaf extract inhibits the development of atherosclerosis in cholesterol-fed rabbits and in cultured aortic vascular smooth muscle cells

This study used high-cholesterol-fed New Zealand white rabbits and aortic vascular smooth muscle cells (VSMCs) to investigate the impact of mulberry leaf extract (MLE) on the development of atherosclerosis. The results show that the major components of MLE are polyphenols, flavonoids, carbohydrates, proteins, and lipids, and the major contituents of mulberry leaf polyphenol extract (MLPE) are polyphenols and flavonoids. In addition to improvement of liver function, the atheroma burden and levels of serum cholesterol, triglycerides, and low-density lipoprotein (LDL) are also significantly reduced after MLE treatment. MLE and MLPE improved endothelial function, inhibited proliferation and migration of aortic VSMCs, and reduced atheromas in the vascular wall. In conclusion, this study demonstrates that, in addition to exerting hypolipidemic effects, MLE and MLPE can effectively inhibit proliferation and migration of aortic VSMCs, improve vascular endothelial function, and reduce atheroma burden, thereby preventing atherosclerosis.

Antioxidant effect of astragalin isolated from the leaves of Morus alba L. against free radical-induced oxidative hemolysis of human red blood cells

We evaluated the antioxidant properties of mulberry leaves extract (MLE) and flavonoids isolated from MLE. MLE was prepared by extraction with methanol. Flavonoids were analyzed by high-performance liquid chromatography. Oxidative hemolysis of normal human red blood cells (RBCs) was induced by the aqueous peroxyl radical [2,2'-Azobis (2-amidinopropane) dihydrochloride, AAPH]. MLE contained three flavonoids in the order quercetin (QC) > kaempferol (KF) > astragalin (AG). Oxidative hemolysis of RBCs induced by AAPH was suppressed by MLE, AG, KF, and QC in a time- and dose-dependent manner. MLE and these three flavonoids prevented the depletion of cystosolic antioxidant glutathione (GSH) in RBCs. AG had the greatest protective effect against AAPH-induced oxidative hemolysis and GSH depletion in RBCs.

Isolation of the putative biosynthetic gene cluster of 1-deoxynojirimycin by Bacillus amyloliquefaciens 140N, its production and application to the fermentation of soybean paste

The 1-deoxynojirimycin (DNJ) biosynthetic gene cluster of Bacillus amyloliquefaciens 140N isolated from traditional Korean fermented food was isolated by PCR screening. It showed 78.9% inhibitory activity against α-glucosidase and produced 0.8 g/L of DNJ in an optimized medium containing 2% soluble starch, 1% tryptone, 0.05% KH(2)PO(4), and 0.05% (NH(2))(4)SO(4). Soybean paste fermented with B. amyloliquefaciens 140N produced DNJ with 84.4% inhibitory activity.

Antiulcer and antioxidant activities of a new steroid from Morus alba

AIMS

Morus alba is a plant that is well known for its medicinal properties. In Asian countries, it is traditionally used for anti-inflammatory, hypoglycemic, hypolipidemic and antioxidant applications. The aim of this study was to evaluate the antiulcer and antioxidant activity of a new steroid from M. alba.

MAIN METHODS

Column chromatography was employed to isolate different compounds from M. alba. The molecular structures of the compounds were characterized via IR, UV, (1)H NMR, (13)C NMR and mass spectroscopic methods. A newly isolated compound was tested for antiulcer activity in pylorus-ligation- and ethanol-induced ulcer models and biochemically estimated for SOD, CAT, GR, GPx, GSH and LPO levels.

KEY FINDINGS

Five new compounds were isolated; one of these was a new steroid named albosteroid. This new compound exhibits significant (P<0.05, P<0.01 and P<0.001) antiulcer activity in pylorus-ligation- and ethanol-induced ulcer models. Furthermore, this compound showed significant dose-dependent reversal of ethanol-diminished activity in antioxidant enzymes, such as SOD, CAT, GPx and GSH, and reduced the ethanol-elevated levels of GR and LPO.

SIGNIFICANCE

The present study clearly demonstrates the anti-ulcer and antioxidant potential of compound 1, which was supported by macroscopic and histopathological studies of stomach wall tissues of differently treated groups of rats.

Chlorogenic acid and rutin play a major role in the in vivo anti-diabetic activity of Morus alba leaf extract on type II diabetic rats

The leaves of the white mulberry tree (Morus alba L.) are used worldwide in traditional medicine as anti-diabetics. Various constituents of mulberry leaves, such as iminosugars (i.e. 1-deoxynojirimicin), flavonoids and related compounds, polysaccharides, glycopeptides and ecdysteroids, have been reported to exert anti-diabetic activity, but knowledge about their contribution to the overall activity is limited. The objective of the present work was to determine the in vivo anti-diabetic activity of an extract of mulberry leaves (MA), and to examine to what extent three major constituents, chlorogenic acid, rutin and isoquercitrin, might contribute to the observed activity. Quantities of the three constituents of interest in the extract were determined by using HPLC-DAD. Activity was determined by using a type II diabetic rat model. After 11 days of per os administration of 250 or 750 mg/kg of MA or the corresponding amounts of each individual compound, a dose dependent decrease of non-fasting blood glucose levels were found for MA, chlorogenic acid and rutin, but not for isoquercitrin. Based on our results, chlorogenic acid and rutin might account for as much as half the observed anti-diabetic activity of MA, hence they can be considered as excellent markers for the quality control of mulberry products.

Assessment of antidiabetogenic potential of fermented soybean extracts in streptozotocin-induced diabetic rat

Most of the available drugs for the treatment of diabetes mellitus (DM) produce detrimental side effects, which has prompted an ongoing search for plant with the antidiabetic potential. The present study investigated the effect of soybean extracts fermented with Bacillus subtilis MORI, fermented soybean extracts (BTD-1) was investigated in streptozotocin (STZ)-induced diabetic rats. The possible effects of BTD-1 against hyperglycemia and free radical-mediated oxidative stress was investigated by assaying the plasma glucose level and the activity of enzymatic antioxidants, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and malondialdehyde (MDA). A significant increase in the levels of both plasma glucose and reactive oxygen species (ROS) was observed in the diabetic rats when compared to normal control group. After administration of BTD-1 (500 and 1000 mg/kg/day), the elevated plasma glucose level was significantly reduced while the plasma insulin level and the activities of SOD, GSH-Px, CAT and MDA were significantly increased. The results suggest that administration of BTD-1 can inhibit hyperglycemia and free radical-mediated oxidative stress. The administration of BTD-1 also inhibited the contractile response by norepinephrine (10(-10)-10(-5) M) in the presence of endothelium, and caused significant relaxation by carbachol (10(-8)-10(-5) M) in rat aorta. These findings indicate that BTD-1 improves vascular functions on STZ-induced diabetic rats. Therefore, subchronic administration of BTD-1 could prevent the functional changes in vascular reactivity in STZ-induced diabetic rats. The collective findings support that administration of BTD-1 may prevent some diabetes-related changes in vascular reactivity directly and/or indirectly due to its hypoglycaemic effect and inhibition of production of ROS.

Mulberrofuran G and isomulberrofuran G from Morus alba L.: anti-hepatitis B virus activity and mass spectrometric fragmentation

Mulberrofuran G (1) and isomulberrofuran G (2), a pair of isomeric Diels-Alder-type adducts, were isolated from the root bark of Morus alba L. Isomulberrofuran G (2) as a new IIB-type Diels-Alder-type adduct, was elucidated by extensive (1)H, (13)C, and two-dimensional (2D) nuclear magnetic resonance (NMR) and mass spectrometry (MS) spectroscopic analyses. A fragmentation study on compounds 1 and 2 was performed by high-resolution electrospray ionization (ESI) multistage tandem mass spectrometry linked with ion-trap (IT) and time-of-flight (TOF) mass analyzers (ESI-MS(n)/IT-TOF) in negative mode, which resulted in obviously different fragmentations. In the MS(2) experiments, the characteristic ions at m/z 451 and 439 could be revealed as their respective diagnostic ions. Mulberrofuran G (1) showed moderate activity, inhibiting hepatitis B virus (HBV) DNA replication with the IC(50) value of 3.99 μM, according to the anti-HBV assay on the HepG 2.2.15 cell line in vitro.

In vitro pharmacokinetic characterization of mulberroside A, the main polyhydroxylated stilbene in mulberry (Morus alba L.), and its bacterial metabolite oxyresveratrol in traditional oral use

Mulberroside A (MulA) is one of the main bioactive constituents in mulberry (Morus alba L.). This study examined the determining factors for previously reported oral pharmacokinetic profiles of MulA and its bacterial metabolite oxyresveratrol (OXY) on in vitro models. When incubated anaerobically with intestinal bacteria, MulA underwent rapid deglycosylation and generated two monoglucosides and its aglycone OXY sequentially. MulA exhibited a poor permeability and predominantly traversed Caco-2 cells via passive diffusion; yet, the permeation of OXY across Caco-2 cells was much more rapid and involved efflux (both p-glycoprotein and MRPs)-mediated mechanisms. Moreover, OXY underwent extensive hepatic glucuronidation; yet, the parent MulA was kept intact in liver subcellular preparations. There was insignificant species difference in intestinal bacterial conversion of MulA and the extent of OXY hepatic glucuronidation between humans and rats, while OXY exhibited a distinct positional preference of glucuronidation in the two species. Overall, these findings revealed a key role of intestinal bacterial conversion in absorption and systemic exposure of MulA and its resultant bacterial metabolite OXY in oral route in humans and rats and warranted further investigational emphasis on OXY and its hepatic metabolites for understanding the benefits of mulberry.

Protection of prenylated flavonoids from Mori Cortex Radicis (Moraceae) against nitric oxide-induced cell death in neuroblastoma SH-SY5Y cells

Seven prenylated flavanoids, licoflavone C (1), cyclomulberrin (2), neocyclomorusin (3), sanggenon I (4), morusin (5), kuwanon U (6) and kuwanon E (7), and three 2-arylbenzofurans, moracin P (8), moracin O (9), and mulberrofuran Q (10) were isolated from the MeOH extract of Mori Cortex Radicis. Among these, compounds 2-7 enhanced cell viability in a dose-dependent manner against sodium nitroprusside-induced cell death in neuroblastoma SH-SY5Y cells, which was measured by MTT reduction assay (EC(50) values of 4.4, 5.6, 8.0, 6.4, 8.7, and 11.9 μg/mL, respectively). Among 10 compounds, C-3 prenylated flavones (2, 3, and 5) and prenylated flavanones (4, 6, and 7) showed cell protection. However, compound 1 which lacks the prenyl group at C-3 and three 2-arylbenzofurans (8-10) did not show protective effect. The order of cell protection was as follow: C-3 prenylated flavones (2, 3, and 5) > prenylated flavanones (4, 6, and 7) > 2-arylbenzofurans (8-10) and flavone (1). From this result, we show that some prenylated flavones and flavanones might protect neuronal cells against nitrosative stress-mediated cell death. Even though further evaluations are necessary in vitro and in vivo study, we carefully suggest that some prenylated flavonoids from Mori Cortex Radicis might protect neuronal cells from neurodegenerative diseases.

Mulberry leaf extract stimulates glucose uptake and GLUT4 translocation in rat adipocytes

Mulberry (Morus alba L.) leaf tea is promoted for its health benefits and the control of diabetes in Asian nations. The blood glucose lowering activity of mulberry leaf extract (MA) has been proven; however, the molecular basis underlying this effect remains unclear. The aim of the present work is to elucidate its mechanism of the antihyperglycemic action, by examining the effect of MA on glucose uptake and the translocation of glucose transporter 4 protein (GLUT4) to the plasma membrane of adipocytes isolated from diabetic rats. The incubation of adipocytes with 5-45 μg/ml MA resulted in 31-54% increase of glucose uptake in a dose-dependent manner. This glucose uptake enhancing effect was inhibited by the phosphoinositol 3-kinase (PI3-K) inhibitor, wortmannin (100 nM). The GLUT4 protein on the plasma membrane fraction of adipocytes was markedly increased after treatment with 15 μg/ml MA extract. Interestingly, gallic acid, one of the phenolic compounds found in MA extract, increased glucose uptake and enhanced the translocation of GLUT4 at concentrations comparable to the amount of gallic acid in the effective concentration ranges of MA. Thus, it is likely that gallic acid contributes, at least in part, to its antihyperglycemic activity. The present results suggest that the antihyperglycemic action of MA is mediated by increasing glucose uptake via the activation of PI3-K signaling pathway and translocation of GLUT4 to the plasma membrane. These findings are the first molecular evidence supporting the mulberry tea as herbal medicine for diabetic patients.

d-Fagomine lowers postprandial blood glucose and modulates bacterial adhesion

d-Fagomine is an iminosugar originally isolated from seeds of buckwheat (Fagopyrum sculentumMoench), present in the human diet and now available as a pure crystalline product. We testedd-fagomine for activities connected to a reduction in the risk of developing insulin resistance, becoming overweight and suffering from an excess of potentially pathogenic bacteria. The activities were: intestinal sucrase inhibitionin vitro(rat mucosa and everted intestine sleeves), modulation of postprandial blood glucose in rats, bacterial agglutination and bacterial adhesion to pig intestinal mucosa. When ingested together with sucrose or starch,d-fagomine lowered blood glucose in a dose-dependent manner without stimulating insulin secretion.d-Fagomine reduced the area under the curve (0–120 min) by 20 % (P < 0·01) and shifted the time to maximum blood glucose concentration (Tmax) by 15 min at doses of 1–2 mg/kg body weight when administered together with 1 g sucrose/kg body weight. Moreover,d-fagomine (0·14 mm) agglutinated 60 % of Enterobacteriaceae (Escherichia coli,Salmonella entericaserovar Typhimurium) populations (P < 0·01), while it did not show this effect onBifidobacteriumspp. orLactobacillusspp. At the same concentration,d-fagomine significantly (P < 0·001) inhibited the adhesion of Enterobacteriaceae (95–99 % cells in the supernatant) and promoted the adhesion ofLactobacillus acidophilus(56 % cells in the supernatant) to intestinal mucosa.d-Fagomine did not show any effect on bacterial cell viability. Based on all this evidence,d-fagomine may be used as a dietary ingredient or functional food component to reduce the health risks associated with an excessive intake of fast-digestible carbohydrates, or an excess of potentially pathogenic bacteria.

Inhibitory effect of 2-arylbenzofurans from the Mori Cortex Radicis (Moraceae) on oxygen glucose deprivation (OGD)-induced cell death of SH-SY5Y cells

Three known 2-arylbenzofurans, moracin P (1), moracin O (2) and mulberrofuran Q (3) were isolated from the MeOH extract of the Mori Cortex Radicis. These compounds 1-3 enhanced cell viability in dose-dependent manner against oxygen-glucose deprivation (OGD)-induced cell death in neuroblastoma SH-SY5Y cells, which was measured by MTT reduction assay. (EC(50) values of 10.4, 12.6, and 15.9 μM, respectively). In addition, the compounds 1-3 were examined for their inhibitory effect on OGD-induced ROS production by FACS analysis. We observed these compounds reduced ROS production in OGD-induced cell death (IC(50) values of 1.9, 0.3 and 12.1 μM, respectively). Consequently, reactive oxygen species (ROS) were overexpressed in OGD-induced cells and all three compounds reduced ROS induced by OGD in dosedependent manner. Taken together, compounds 1-3 might protect neuronal cell death against the oxidative stress induced by OGD, though further studies in vitro and in vivo models are necessary.

Production of plant proteases in vivo and in vitro--a review

In the latest two decades, the interest received by plant proteases has increased significantly. Plant enzymes such as proteases are widely used in medicine and the food industry. Some proteases, like papain, bromelain and ficin are used in various processes such as brewing, meat softening, milk-clotting, cancer treatment, digestion and viral disorders. These enzymes can be obtained from their natural source or through in vitro cultures, in order to ensure a continuous source of plant enzymes. The focus of this review will be the production of plant proteases both in vivo and in vitro, with particular emphasis on the different types of commercially important plant proteases that have been isolated and characterized from naturally grown plants. In vitro approaches for the production of these proteases is also explored, focusing on the techniques that do not involve genetic transformation of the plants and the attempts that have been made in order to enhance the yield of the desired proteases.

Effect of mulberry leaf extract with enriched 1-deoxynojirimycin content on postprandial glycemic control in subjects with impaired glucose metabolism

Aims/Introduction:  The glucose analogue, 1-deoxynojirimycin (DNJ), found in mulberry (Morus alba) leaves, is a promising α-glucosidase inhibitor. We evaluated the effect of the ingestion of mulberry leaf extract with enriched DNJ content on postprandial hyperglycemia in subjects with impaired glucose metabolism.

MATERIALS AND METHODS

  In study 1, we carried out a randomized, double-blind, crossover trial to assess the effects of single ingestion of mulberry leaf extract (3, 6 or 9 mg DNJ) or placebo on blood glucose and insulin concentrations during 2 h after a carbohydrate (200 g boiled white rice) challenge in 12 subjects with fasting plasma glucose (FPG) in the range of 100-140 mg/dL. Study 2 was a randomized, double-blind, placebo-controlled trial to assess the efficacy of 12-week extract supplementation (6 mg DNJ, t.i.d.) for long-term glycemic control in 76 subjects with FPG in the range of 110-140 mg/dL.

RESULTS

  In study 1, ingestion of the mulberry leaf extract led to attenuated postchallenge acute glycemia in a dose-dependent manner (P = 0.006, group × time interaction, two-way anova). In study 2, the serum 1,5-anhydroglucitol concentration, a sensitive indicator of postprandial glycemic control, in the extract group increased and was higher than that in the placebo group over the 12-week treatment period (P < 0.001, group × time interaction, two-way anova); no differences in FPG, glycated hemoglobin and glycated albumin concentrations were observed between the groups.

CONCLUSIONS

  Long-term ingestion of mulberry leaf extract with enriched DNJ content could result in improved postprandial glycemic control in individuals with impaired glucose metabolism. These trials were registered with UMIN (no. UMIN000003154 and UMIN000003155). (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00101.x, 2011).

Anti-cancer activity of 5-O-alkyl 1,4-imino-1,4-dideoxyribitols

New derivatives of 1,4-dideoxy-1,4-imino-D-ribitol have been prepared and evaluated for their cytotoxicity on solid and haematological malignancies. 1,4-Dideoxy-5-O-[(9Z)-octadec-9-en-1-yl]-1,4-imino-D-ribitol (13, IC(50) ∼2 μM) and its C(18)-analogues (IC(50) <10 μM) are cytotoxic toward SKBR3 (breast cancer) cells. 13 also inhibits (IC(50) ∼8 μM) growth of JURKAT cells.

Comparison of 1-deoxynojirimycin and aqueous mulberry leaf extract with emphasis on postprandial hypoglycemic effects: in vivo and in vitro studies

Carbohydrate digestion by α-glucosidase and subsequent glucose uptake at the brush border are critical for postprandial blood glucose control. Any specific inhibitors are useful as hyperglycemia modulating agents. In this study, it was postulated that an array of active components in mulberry leaf extract (MLE) may provide higher potency in inhibiting intestinal glucose absorption compared to the single component 1-deoxynojirimycin (DNJ), which is recognized as a promising inhibitor of intestinal glucose absorption. Both MLE and DNJ were active in inhibiting α-glucosidase. However, in Caco-2 cells, only MLE showed significant inhibition of 2-deoxyglucose uptake, whereas DNJ was ineffective. For glucose loading, co-administration of MLE resulted in potent inhibitions of glucose responses compared to those by DNJ in Sprague Dawley (SD) rats, but this was not found for maltose loading. These novel findings add evidence that the unabsorbed phytochemicals in MLE compete with glucose for intestinal glucose transporters, but DNJ itself does not. We also evaluated the timing of MLE consumption. By administering MLE for 30 min before glucose loading, the incremental area under the curve (IAUC) was significantly lowered in the rats, as compared to a simultaneously administered group. Similarly, cellular glucose uptake was significantly reduced in Caco-2 cells following pretreatment.

Efficacy of silkworm (Bombyx mori L.) chrysalis oil as a lipid source in adult Wistar rats

The effects of silkworm chrysalis oil, rich in n-3 α-linolenic acid (ALA), on lipid metabolism in Wistar rats were investigated. The rats were fed diets containing 7% soybean oil (control), silkworm chrysalis oil (SWO), or fish oil (FO) for 8weeks. Plasma triglyceride and glucose levels were significantly lower in the SWO group after 8weeks compared to the control and FO groups. The total cholesterol and blood urea nitrogen levels were higher in the control group than in the SWO and FO groups at 8weeks post-consumption. However, aspartate amino transferase and alanine amino transferase levels were not significantly different among all groups. A higher arachidonic acid (AA) content was detected in the control group, while lower AA levels were observed with the increase in EPA and DHA in the SWO and FO groups. These results suggest that n-3 α-linolenic acid-rich silkworm chrysalis oil can improve hyperlipidaemia and hyperglycaemia.