Mining and functional characterization of NADPH-cytochrome P450 reductases of the DNJ biosynthetic pathway in mulberry leaves

BACKGROUND

1-Deoxynojirimycin (DNJ), the main active ingredient in mulberry leaves, with wide applications in the medicine and food industries due to its significant functions in lowering blood sugar, and lipids, and combating viral infections. Cytochrome P450 is a key enzyme for DNJ biosynthesis, its activity depends on the electron supply of NADPH-cytochrome P450 reductases (CPRs). However, the gene for MaCPRs in mulberry leaves remains unknown.

RESULTS

In this study, we successfully cloned and functionally characterized two key genes, MaCPR1 and MaCPR2, based on the transcriptional profile of mulberry leaves. The MaCPR1 gene comprised 2064 bp, with its open reading frame (ORF) encoding 687 amino acids. The MaCPR2 gene comprised 2148 bp, and its ORF encoding 715 amino acids. The phylogenetic tree indicates that MaCPR1 and MaCPR2 belong to Class I and Class II, respectively. In vitro, we found that the recombinant enzymes MaCPR2 protein could reduce cytochrome c and ferricyanide using NADPH as an electron donor, while MaCPR1 did not. In yeast, heterologous co-expression indicates that MaCPR2 delivers electrons to MaC3'H hydroxylase, a key enzyme catalyzing the production of chlorogenic acid from 3-O-p-coumaroylquinic acid.

CONCLUSIONS

These findings highlight the orchestration of hydroxylation process mediated by MaCPR2 during the biosynthesis of secondary metabolite biosynthesis in mulberry leaves. These results provided a foundational understanding for fully elucidating the DNJ biosynthetic pathway within mulberry leaves.

Rapid Screening of Nonalkaloid α-Glucosidase Inhibitors from a Mulberry Twig Extract Using Enzyme-Functionalized Magnetic Nanoparticles Coupled with UPLC-MS/MS

Mulberry twigs are an important source of α-glucosidase inhibitors. To date, research studies on α-glucosidase in mulberry twigs have mainly focused on alkaloids such as 1-deoxynojirimycin (DNJ). Preliminary studies have shown that there may be more active nonalkaloid α-glucosidase inhibitors in mulberry twigs. In this study, we immobilized α-glucosidase on Fe₃O₄@SiO₂ for the first time and rapidly screened four nonalkaloid α-glucosidase inhibitors (kuwanon G, kuwanon C, kuwanon H, and morusin) using ligand fishing technology with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) from the mulberry twig extract of Jialing 20, the excellent artificial triploid variety of mulberry cultivated extensively in Southwest China. The half maximal inhibitory concentrations (IC₅₀) of kuwanon H and kuwanon G were 2.82 ± 0.68 and 2.83 ± 0.31 μM, respectively, with better inhibition activity than that of DNJ (with an IC₅₀ of 7.04 ± 0.82 μM). Meanwhile, the molecular docking results showed that the action sites of these two isopentenyl flavonoids on α-glucosidase were different from that of DNJ. In brief, this work is beneficial to discovering new α-glucosidase inhibitors from mulberry twigs quickly and accurately and provides a theoretical basis for the mulberry twig extract as a functional food or a natural hypoglycemic drug source, as well as a reference for directional breeding of mulberry, which greatly improves the exploitation and utilization value of mulberry twigs as an agricultural byproduct in the fields of agricultural production, functional food, and natural medicine.

Screening, cloning and functional characterization of key methyltransferase genes involved in the methylation step of 1-deoxynojirimycin alkaloids biosynthesis in mulberry leaves

The novel C-methyltransferase, MaMT1, could catalyze the conversion of piperidine to 2-methylpiperidine, which may be involved in the methylation step of DNJ biosynthesis in mulberry leaves. Mulberry (Morus alba L.) is a worldwide crop with medicinal, feeding and nutritional value, and 1-deoxynojirimycin ((2R, 3R, 4R, 5S)-2-hydroxymethyl-3, 4, 5-trihydroxypiperidine, DNJ) alkaloid, a potent α-glucosidase inhibitor, is its main active ingredient. Our previous researches clarified the biosynthetic pathway of DNJ from lysine to Δ¹-piperideine, but its downstream pathway is unclear. Herein, eight differential methyltransferases (MTs) genes were screened from transcriptome profiles of mulberry leaves with significant differences in DNJ content (P < 0.01). Subsequently, MaMT1 (OM140666) and MaMT2 (OM140667) were hypothesized as candidate genes related to DNJ biosynthesis by correlation analysis of genes expression levels and DNJ content of mulberry leaves at different dates. Functional characterization of MaMT1 and MaMT2 were performed by cloning, prokaryotic expression and enzymatic reaction in vitro, and it showed that MaMT1 protein could catalyze the conversion of piperidine to 2-methylpiperidine. Moreover, molecular docking confirmed the interaction of MaMT1 protein with piperidine and S-adenosyl-L-methionine (SAM), indicating that MaMT1 had C-methyltransferase activity, while MaMT2 did not. The above results suggested that MaMT1 may be involved in the methylation step of DNJ alkaloid biosynthesis in mulberry leaves, which is a breakthrough in the analysis of DNJ alkaloid biosynthetic pathway. It is worth mentioning that the novel MaMT1, annotated as serine hydroxymethyltransferase, could rely on SAM to perform C-methyltransferase function. Therefore, our findings contribute new insights into the research of DNJ alkaloid biosynthesis and C-methyltransferase family.

Chemometric evaluation of functional components and anti-quorum sensing activity of mulberry leaves from Indian cultivars: a potential contribution to the food industry

BACKGROUND

Potential use of many native, easily available vegetal materials for human consumption and value addition is not well recognized. Mulberry, being a traditional industrial crop rich in nutrients and nutraceuticals can be of great importance for the food industry. However, mulberry leaves are mainly being utilized in sericulture and are not exploited for their functional components. Thus, the selection of promising mulberry cultivars, rich in bioactive compounds, like resveratrol and 1-deoxynojirimycin, increase their potential use in functional foods.

RESULTS

Chlorogenic acid, myricetin and kaempferol were the major polyphenols present in the nine selected cultivars, in the range 0.001-0.086, 0.003-0.079 and 0.003-0.163 g kg^-1 fresh weight (FW), respectively. Protocatechuic acid, epicatechin and rutin were predominantly present in cultivars V-1, G-2 and ML (0.103, 0.080 and 0.121 g kg^-1 FW, respectively). Similarly, resveratrol and 1-deoxynojirimycin were highest in cultivars ML and K-2 (0.078 and 0.079 g kg^-1 FW, respectively). Leaf extracts of cultivars G-2 and ML were able to effectively inhibit the violacein production with 64.08% and 70.04%, respectively at the concentration of 6 mg mL^-1 presumably due to a higher content of polyphenols. Chemometric evaluation of chromatographic data showed the intraspecific variability and secondary metabolite co-existence in different cultivars.

CONCLUSIONS

Considering phytoconstituents, cultivars G-2, ML, K-2 and V-1 could contribute efficiently to the rational utilization of mulberry in agro-food industries. Furthermore, cultivars G-2 and ML leaves can be a new source of quorum sensing inhibitory agents. © 2021 Society of Chemical Industry.

Total flavonoids, total phenolics, 1-deoxynojirimycin content and alpha-glucosidase inhibitory activity of Thai silkworm races (Bombyx mori Linn.)

The silkworm powder (Bombyx mori Linn.) from Japanese and Korean races has well known used as a blood glucose lowering substance. However, the study of bioactive compounds and hypoglycemic effect on Thai silkworm races is still limited. This study was aimed to investigate the flavonoid, phenolic and 1-deoxynojirimycin (DNJ) contents, and α-glucosidase inhibitory activity of three Thai silkworm races (Nanglai, Nangnoi and Samrong) of the 5th instar, 2nd 4th day silkworm powders. The total flavonoid, phenolic contents and α-glucosidase inhibitory activity were performed using spectrophotometric methods. The DNJ content was determined using derivatization and further analyzed by HPLC. Nangnoi showed the highest flavonoid content with 12.32±0.41mg quercetin equivalent/g silkworm powder. Nanglai showed the highest phenolic content with 78.74±1.43mg gallic acid equivalent/g silkworm powder. Regarding DNJ content, Nangnoi expressed the highest at 3.11±0.01mg/g silkworm powder. According to the age of silkworm, powders of the instar 5th, day 3rd were provided the highest α-glucosidase inhibitory activity (p<0.05). This study clearly indicated that the 5th instar, 3rd day of Thai silkworms exhibited the highest flavonoid, phenolic, DNJ contents and α-glucosidase inhibitory activity. Further study on blood glucose lowering activity should be performed.

Determination of 1-Deoxynojirimycin by a developed and validated HPLC-FLD method and assessment of In-vitro antioxidant, α-Amylase and α-Glucosidase inhibitory activity in mulberry varieties from Turkey

BACKGROUND

Morus alba and Morus nigra leaves which have been widely used as herbal teas in Anatolian region of Turkey, were extracted twice by 50 mM HCI solution, derivatized with 9-fluorenylmethyl chloroformate and analyzed by reversed phase HPLC equipped with a fluorescence detector.

HYPOTHESIS/PURPOSE

This study was performed to determine the main antidiabetic active compounds 1-deoxynojirimycin by HPLC method and evaluate the in-vitro antioxidant and antidiabetic activity of ethanol extracts prepared from Morus alba L. and Morus nigra leaves.

STUDY DESIGN

A reliable simple, and rapid high-performance liquid chromatographic (HPLC) method for the determination of 1-deoxynojirimycin in M. alba L. and M. nigra leaves with fluorimetric detection after pre-column derivatization with 9-fluorenylmethyl chloroformate was developed. In addition, the chemical composition of ethanol extract of mulberry leaves was analyzed with GC-MS.

METHODS

Separation and quantitation were performed on C18, 250 × 4.6 mm, 5 µm analytical column. Mobile phase consisted of acetonitrile and 0.1% acetic acid solution (1:1, v/v) was performed applied to the column 1.0 ml/min flow rate at 26 °C. Potential antioxidant activity of ethanol extract of different mulberry varieties were evaluated by DPPH, and ABTS radical scavenging assay as well as total phenol and flavonoid content were determined. In addition, α-amylase and α-glucosidase activity was determined by 96-well plate method to evaluate the probable antidiabetic potential use of Turkish mulberry leaves.

RESULTS

The isocratic HPLC method showed excellent correlation coefficient (r²= 0.9985) between 0.3 and 30 µg/ml calibration points. The method was specific and sensitive with detection and quantification limits of 1.07 and 3.27 ng/ml, respectively. Intraday and interday method precision (n = 5) were < 7.3 (RSD%). Intraday and interday method accuracy (n = 5) were between 3.77 and (-8.35) (RE%). The average method recovery (n = 3) was 102.5%. The results showed that the content of 1-deoxynojirimycin in leaves of Morus alba L. was 0.103% (n = 3), and in leaves of M. nigra L. was 0.102%. 2-hexadecen-1-ol, oleamide, 2-propenoic acid, and cyclododecane were identified as the major compounds by GC-MS in the ethanol extract of mulberry leaves.

CONCLUSION

The obtained robustness values from emission and excitation detection, mobile phase ingredients and flow rates changes showed that method was very strong. This work contributes to the knowledge of antioxidant and antidiabetic properties of Morus species, thus may be provide useful data in evaluation of food products and pharmaceutical preparations produced from Morus species.

Evaluation of the anti-hyperglycemic effect and safety of microorganism 1-deoxynojirimycin

1-Deoxynojirimycin (DNJ) is a potent α-glucosidase inhibitor and thus beneficial for prevention of diabetes. While we have succeeded in obtaining the culture supernatant extract (CSE) rich in DNJ from microorganism source, information regarding its anti-hyperglycemic effect and safety were still limited. Therefore, this study was aimed to evaluate the anti-hyperglycemic effect and safety of microorganism DNJ. Oral sucrose tolerance test was performed, and the result showed that CSE was able to significantly suppress the blood glucose elevation and suggested DNJ as the main active compound. To determine its safety, the absorption and excretion of microorganism DNJ were evaluated using 15N labeling method. Our findings investigated the recovery rate of 15N from DNJ reached 80% up to 48 hours after oral administration, suggesting its rapid excretion, suggesting the safety of DNJ. This study verified the functional properties and safety of DNJ from microorganisms, suggesting its potential use for functional purpose.

Metabolic Effect of 1-Deoxynojirimycin from Mulberry Leaves on db/db Diabetic Mice Using Liquid Chromatography-Mass Spectrometry Based Metabolomics

Metabolomics was applied to the liquid chromatography-mass spectrometry urinary metabolic profile of type 2 diabetes (T2DM) mice treated with mulberry 1-deoxynojirimycin (DNJ). The serum biochemical indicators related to T2DM like blood glucose, insulin, triglyceride, total cholesterol, nitrogen, malondialdehyde, and creatinine decreased significantly in the treated group. The histopathological changes in liver cells were marked by deformations and disruptions in central area of nuclei in DM mice, whereas DNJ treatment recovered regular liver cells with normal nuclei. Most of the metabolites of T2DM were significantly different from healthy controls in the bulk data generated. The level of 16 metabolites showed that the diabetic group was closer to the healthy group as the DNJ treatment time prolonged. Moreover, DNJ inhibited the activity of glucosidase on glucose, lipid, and amino acid metabolism. Our results showed the mechanism of DNJ treatment of T2DM and could fetch deep insights into the potent metabolite markers of the applied antidiabetic interventions.

Effects of Applied Nitrogen Amounts on the Functional Components of Mulberry (Morus alba L.) Leaves

This study investigated the effects of applied nitrogen amounts on specific functional components in mulberry (Morus alba L.) leaves. The relationships between mineral elements and the functional components in mulberry leaves were examined using mulberry trees cultivated in different soil conditions in four cultured fields. Then, the relationships between the nitrogen levels and the leaf functional components were studied by culturing mulberry in plastic pots and experimental fields. In the common cultured fields, total nitrogen was negatively correlated with the chlorogenic acid content (R(2) = -0.48) and positively correlated with the 1-deoxynojirimycin content (R(2) = 0.60). Additionally, differences in nitrogen fertilizer application levels affected each functional component in mulberry leaves. For instance, with increased nitrogen levels, the chlorogenic acid and flavonol contents significantly decreased, but the 1-deoxynojirimycin content significantly increased. Selection of the optimal nitrogen application level is necessary to obtain the desired functional components from mulberry leaves.

Rapid identification of miglitol and its isomers by electrospray ionization tandem mass spectrometry

RATIONALE

Miglitol (1) derived from 1-deoxynojirimycin is an iminosugar that is useful in the treatment of type 2 diabetes mellitus. Isomers (2, 3, 4) that differ at the C2 and C3 positions of hydroxyl groups from miglitol are impurities resulting from the synthesis of miglitol. The impurity profile of a drug substance is critical to its safety assessment and is important for monitoring the manufacturing process. Therefore, developing a fast and simple method that can rapidly identify the configuration of miglitol and its isomers (2, 3, 4) is necessary.

METHODS

Miglitol (1) and its isomers 2-4 were derivatized with benzoboroxole (o-hydroxymethyl phenylboronic acid) at room temperature, and the cyclic boronate esters of different configurations were generated. Protonated miglitol and its isomers 2-4, as well as their derivatives, were subjected to collision-induced dissociation (CID) experiments by using electrospray ionization tandem mass spectrometry (ESI-MS/MS). Elemental compositions of all the ions were verified by electrospray ion-trap time-of-flight mass spectrometry.

RESULTS

Fragmentation of the protonated miglitol and its isomers gave the same fragment ions at m/z 190 and m/z 146. Both their fragmentation behavior and abundances were similar. Whereas the CID mass spectra of the precursor ions (m/z 322) of cyclic boronate esters showed four characteristic fragment ions, m/z 214 ([M-C7 H8 O](-) ), m/z 196 ([M-C7 H8 O-H2 O](-) ), m/z 151 ([M-C8 H13 NO3 ](-) ), and m/z 133 ([M-C8 H15 NO4 ](-) ). The abundances of these fragments are different which are related to the stereostructure of miglitol and its isomers.

CONCLUSIONS

A facile method was established for the differentiation of the spatial configuration of miglitol and its isomers using the relative abundances of the fragment ions of boronate esters generated from in-situ reaction between analytes and benzoboroxole by ESI-MS/MS. This approach could be used to rapidly identify the stereoisomers and monitor the epimerization of miglitol and its isomers in chemical reactions and manufacturing processes. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of solar radiation on the functional components of mulberry (Morus alba L.) leaves

BACKGROUND

The functional components of mulberry leaves have attracted the attention of the health food industry, and increasing their concentrations is an industry goal. This study investigated the effects of solar radiation, which may influence the production of flavonol and 1-deoxynojirimycin (DNJ) functional components in mulberry leaves, by comparing a greenhouse (poor solar radiation) and outdoor (rich solar radiation) setting.

RESULTS

The level of flavonol in leaves cultivated in the greenhouse was markedly decreased when compared with those cultivated outdoors. In contrast, the DNJ content in greenhouse-cultivated plants was increased only slightly when compared with those cultivated outdoors. Interestingly, the flavonol content was markedly increased in the upper leaves of mulberry trees that were transferred from a greenhouse to the outdoors compared with those cultivated only in the outdoors.

CONCLUSION

Solar radiation conditions influence the synthesis of flavonol and DNJ, the functional components of mulberry leaves. Under high solar radiation, the flavonol level becomes very high but the DNJ level becomes slightly lower, suggesting that the impact of solar radiation is great on flavonol but small on DNJ synthesis. © 2016 Society of Chemical Industry.

[Study on quality standard for mori cortex]

OBJECTIVE

To establish a new evaluation model and compare the differences of Mori Cortex from different habitats at different harvest time.

METHODS

TLC method was used to identify sanggenon D in the sample with silica gel G plate and a mixture of chloroform-methanol-formic acid (5: 1:0. 3) as a developing solvent. UV was used for determination the centent of total flavonoids of Mori Cortex with sanggenon C as the reference substance. HPLC was applied for determination the contents of sanggenons C, D and DNJ of Mori Cortex.

RESULTS

In the TLC chromatogram, sanggenon D showed a distinct fluorescence spot under UV 365 nm with good separation. In UV, sanggenon C calibration curve showed a good linear relationship at the range of 146.8 - 734.0 microg/mL, the average recovery was 97.4% (RSD = 2.1%); For the HPLC quantitation method, sanggenons C, D and DNJ showed good linear within the scope of 700 - 4 000 microg, 500 - 3 000 microg and 4.8 - 96 microg, respectively. The average recovery of sanggenons C, D and DNJ were 98.8% (RSD = 2.6%), 99.1% (RSD = 2.2%) and 98.9% (RSD = 1.7%), respectively. The contents of index components in samples from different habitats at different harvest time were different.

CONCLUSION

The established method is reliable and accurate. It can be used for quality control of Mori Cortex.

[Correlation of DNJ between taxilli herba and its host-plants]

OBJECTIVE

To study the correlation of 1-deoxynojirimycin (DNJ) between Taxilli Herba parasitized in mulberry and its host-plants.

METHOD

The contents of DNJ of Taxilli Herba parasitized in mulberry and non-mulberry were determined by RP-HPLC. DNJ was extracted with 0.05 mol x L(-1) HCl, and then detected by fluorescence detector after derivatized with FMOC-Cl at pH 8.0 with borate buffer. The separation was performed on an Agilent C18 (4.6 mm x 250 mm, 5 microm) column with a mobile phase of acetonitrile-0.1% aqueous acetic acid (51: 49) at a flow rate of 1.0 mL x min(-1). The wavelength of fluorescence detector was operated at lambda(EX) = 254 nm and lambda(EM) = 322 nm.

RESULT

The linear range of DNJ was 3.72-37.2 mg x L(-1) (r = 0.999 9). The average recovery was 96.42%. The contents of DNJ in mulberry and Taxilli Herba parasitized in mulberry were 1.39-10.16 mg x g(-1) and 0.46-2.72 mg x g(-1), respectively. However, the contents of DNJ could not be detected in Taxilli Herba parasitized in non mulberry and its host-plants.

CONCLUSION

As the characteristic constituent of mulberry, DNJ was accumulated in Taxilli Herba This method can be applied to the quality control of Taxilli Herba from mulberry.

Development and validation of HPLC-UV-MS method for the control of four anti-diabetic drugs in suspected counterfeit products

An HPLC-UV method has been developed for the determination of valibose, miglitol, voglibose and acarbose, the four anti-diabetic drugs. The separation was accomplished successfully by using reversed phase chromatography (Prevail carbohydrate column, 250 mm x 4.6 mm, 5 microm) with a gradient acetonitrile-phosphate buffer solution (pH 8.0) at a wavelength of 210 nm. Furthermore, the method of a high-performance liquid chromatography coupled with ESI-MS in positive ionization mode has been established. These two methods were successfully applied to the assay and qualitative detection of four alpha-glucosidase inhibitors in the potential counterfeit anti-diabetic drugs.

Phytochemical profiles of different mulberry (Morus sp.) species from China

Mulberry is rich in alkaloids, polyphenols, flavonoids, and anthocyanins, which have been suggested to be responsible for health benefits. The concentrations of 1-deoxynojirimycin (DNJ), resveratrol, oxyresveratrol, cyanidin-3-O-beta-glucoside (Cy-3-glu), cyanidin-3-O-beta-rutinoside (Cy-3-rut), and rutin in mulberry juice, fruits, and leaves of 8 species grown in China were examined. It is the first time content determination of DNJ in mulberry juice and oxyresveratrol in mulberry fruits and leaves has been reported. Among the varieties tested, Da 10 (Morus atropurpurea Roxb.) was the most valuable cultivar considering its high content of functional components. Besides, Hetianbaisang (M. alba Linn.), Taiwanguosang (M. atropurpurea Roxb.), Fujian 2 hao (M. alba Linn.), Gaozhoujisang (M. australis Poir.), and Shanxiguosang (M. nigra Linn.) were rich in DNJ, resveratrol, oxyresveratrol, anthocyanins, and flavonoids, respectively. The high contents of functional compounds in mulberry juice, fruits, and leaves implied that they might be potential resources for the development of functional drinks and food.

[Quantitative determination of 1-deoxynojirimycin in mulberry leaves by high-performance liquid chromatographic-tandem mass/mass spectrometry]

OBJECTIVE

To develop a high-performance liquid chromatographic-tandem mass/mass spectrometric method to determine the concentration of 1-deoxynojirimycin (1-DNJ) in mulberry leaves.

METHODS

1-deoxynojirimycin was separated on an SHIMADZU HRC-NH2 column with the mobile phase consisting of acetonitrile and 0.1% formic acid. The mass spectrometric system equipped with a atmospheric pressure chemical ionization (APCI) interface was operated in Multiple Reaction Monitoring (MRM) mode.

RESULTS

The retention time of 1-deoxynojirimycin was 2.87 min, and the calibration curve was linear over a concentration range from 482 microg/L to 2410 microg/L, the average recovery was 95.8%. The detection limit was 53.6 microg/L.

CONCLUSION

The method is selective and sensitive for determining 1-deoxynojirimycin in mulberry leaves.

[Determination of 1-deoxynojirimycin in Morus alba L. leaves using reversed-phase high performance liquid chromatography fluorescence detection with pre-column derivatization]

A rapid, reliable and suitable method for the determination of 1-deoxynojirimycin (DNJ) in Morus alba L. leaves has been developed. The DNJ in 100 mg dried leaves was extracted twice with 10 mL aqueous 0.05 mol/L HCl, then derivatized by 6-aminoquinoiyi-N-hydroxysuccinimidyl carbamate (AQC) in K3BO3 buffer (pH 8.5), and analyzed using a high performance liquid chromatograph equipped with a fluorescence detector. The analyte was eluted with a mobile phase of 0.02 mol/L potassium dihydrogen phosphate buffer-acetonitrile (85: 15, v/v) at the rate of 1.0 mL/min. The derivatized DNJ was well dissolved from the hydrolysis products of AQC. The linearity ranged from 0.5 to 25 mg/L, and the detection limit was 0.02 mg/L (S/N = 3). The content of DNJ in Morus alba L. leaves was 0.12%, the recovery was 96.1%-98.6%.

[Contrast of 1-deoxynojirimycin content in mulberry leaves from different habitats]

OBJECTIVE

To Contrast the content of 1-deoxynojirimycin in Mulberry Leaves from different habitats.

METHODS

The samples were analyzed by high performance liquid chromatography equipped with fluorescence detector and separated on HiQSiLC18 column at 25 degrees C. Mobile phase consisted of acetonitrile-0.1% aqueous acetic acid (55: 45) with a flow rate of 1.0 ml x min(-1). The fluorescence detector was operated at lambdaEX = 254 nm, lambdaEM = 322 nm.

RESULTS

The contents of 1-deoxynojirimycin from different habitats of Mulberry Leaves were remarkably different, while those from the same habitats but different species or varieties were different too.

CONCLUSION

The result can offer the proof for exploiting the resource of Mulberry Leaves preferably.

Quantitative determination of 1-deoxynojirimycin in mulberry leaves using liquid chromatography–tandem mass spectrometry

A novel HPLC-MS/MS method was developed for the quantitative determination of 1-deoxynojirimycin (DNJ), a potent glucosidase inhibitor present in mulberry leaves (Morus alba L.). DNJ was isolated from the mulberry leave extract on a TSKgel Amide-80 column using a mixture of 0.1% formic acid and acetonitrile as a mobile phase at a flow rate of 0.6 ml/min. A triple quadrupole mass spectrometry using electrospray ionization source in a positive ion mode under multiple reaction monitoring with the [M+H]+ ions, m/z 164.4/109.9 was used. The detection limit (S/N=3) was 75 pg and quantitation limit (S/N=10) was 100 pg. The comparison of mulberry leaves of different ages showed that the DNJ level was higher in mulberry shoots than young and mature leaves.

Food-grade mulberry powder enriched with 1-deoxynojirimycin suppresses the elevation of postprandial blood glucose in humans

Mulberry 1-deoxynojirimycin (DNJ), a potent glucosidase inhibitor, has been hypothesized to be beneficial for the suppression of abnormally high blood glucose levels and thereby prevention of diabetes mellitus. However, DNJ contents in commercial mulberry products were as low as about 0.1% (100 mg/100 g of dry product), implying that the bioavailability of DNJ might not be expected. We carried out studies in two directions: (1) production of food-grade mulberry powder containing a maximally high DNJ content; (2) determination of the optimal dose of the DNJ-enriched powder for the suppression of the postprandial blood glucose through clinical trials. The following method was used: (1) DNJ concentrations in mulberry leaves from different cultivars, harvest seasons, and leaf locations were determined using hydrophilic interaction chromatography with evaporative light scattering detection. (2) Healthy volunteers received 0, 0.4, 0.8, and 1.2 g of DNJ-enriched powder (corresponding to 0, 6, 12, and 18 mg of DNJ, respectively), followed by 50 g of sucrose. Before and 30-180 min after the DNJ/sucrose administration, plasma glucose and insulin were determined. The following results were obtained: (1) Young mulberry leaves taken from the top part of the branches in summer contained the highest amount of DNJ. After optimization of the harvesting and drying processes for young mulberry leaves (Morus alba L. var. Shin ichinose), DNJ-enriched powder (1.5%) was produced. (2) A human study indicated that the single oral administration of 0.8 and 1.2 g of DNJ-enriched powder significantly suppressed the elevation of postprandial blood glucose and secretion of insulin, revealing the physiological impact of mulberry DNJ (effective dose and efficacy in humans). This study suggests that the newly developed DNJ-enriched powder can be used as a dietary supplement for preventing diabetes mellitus.

[Chemical constituents from leaves of Morus multicaulis]

OBJECTIVE

To study the chemical constituents from the leaves of Morus multicaulis.

METHOD

The compounds were isolated by ion exchange resin, silica gel and Sephadex LH -20 column chromatographies. Their structures were elucidated on the basis of physico-chemical properties and spectral data.

RESULT

Twelve compounds were isolated from the leaves of this plant. Their structures were identified as 1-deoxynojirimycin (1), fagomine (2), 2-O-alpha-D-galactopyranosyl-1-deoxynojirimycin (3), quercetin-7-O-beta-D-glucoside (4), kaempferol (5), quercetin (6), scopoletin (7), D-aspartic acid (8), L-proline (9), D-alpha-alanine (10), myo-inositol (11) and dausterol (12).

CONCLUSION

All compounds were isolated from this plant for the first time.

1-Deoxynojirimycin Derivatives from the Marine Sponge Lendenfeldia chondrodes

Two 1-deoxynojirimycin derivatives, 1-deoxynojirimycin-6-phosphate (1) and N-methyl-1-deoxynojirimycin-6-phosphate (2) were isolated from an aqueous extract of Micronesian marine sponge Lendenfeldia chondrodes for the first time as natural products. Structures of these compounds were assigned on the basis of their spectral data and chemical degradation.

[Determination of 1-deoxynojirimycin in leaves of Morus alba by high performance liquid chromatography with fluorescence detection]

OBJECTIVE

To develop a high performance liquid chromatographic method for the determination of DNJ in Morus alba leaves with fluorimetric detection after precolumn derivatization with 9-fluorenylmnethyl chlorformate (FMOC-Cl).

METHOD

DNJ in Morus alba leaves was extracted with 0.05 mol x L(-1) HCl, reacted with FMOC-Cl, and separated on a HiQSiL C18 column at 250 degrees C. Mobile phase consisted of acetonitrile-0.1% aqueous acetic acid (55:45) with a flow rate of 1.0 mL x min. The fluorescence detector was operated at lambdaEX = 254 nm, lambdaEM = 322 nm.

RESULT

A satisfactory separation between DNJ and impurity was obtained. The calibration curve was linear over the concentration range from 0.567 microg x mL(-1) to 34 microg mL(-1), r = 0.9998. The average recovery was 97.2%. The contents of DNJ in M. alba collected in different seasons and grown in different environment were determined.

CONCLUSION

The quantity of DNJ in leaves of M. alba is related to the environment factor, temperature and growing period. The method can be used for qualioy control of the medicinal material.

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.

Simple and rapid determination of 1-deoxynojirimycin in mulberry leaves

A simple and rapid method for determining 1-deoxynojirimycin (DNJ), a potent glucosidase inhibitor 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 extract of mulberry leaves on TSK gel Amide-80 column, which is a representative column for hydrophilic interaction chromatography. During post column 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.

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.

Rapid monitoring of site-specific glycosylation microheterogeneity of recombinant human interferon-gamma

An analytical system is presented for rapid assessment of site-specific microheterogeneity of the two potential N-linked glycosylation sites of recombinant human interferon-gamma (IFN-gamma) derived from Chinese hamster ovary cell culture. The target protein is first purified from culture supernatant by immunoaffinity chromatography, and the acidic eluent is neutralized via an in-line mixing tee. On-line proteolysis is rapidly performed by an immobilized trypsin cartridge, and reversed-phase chromatography isolates the two pools of glycopeptides representing the potential glycosylation sites. Following off-line analysis by matrix-assisted laser-desorption ionization/time-of-flight (MALDI/TOF) mass spectrometry, observed mass shifts of glycopeptides relative to the known masses of their amino acid portions are correlated to site-specific oligosaccharide structures. Desialylation of glycopeptides by sialidase treatment on the MALDI sample plate allows for quantitative estimations of asialoglycan structures by MALDI/TOF. This methodology permits glycoprotein microheterogeneity to be evaluated in a time frame of approximately 2 h, utilizing as little as 0.5 microgram (25 pmol) of product. Results of monitoring a batch culture are presented as well as analysis of a culture containing deoxymannojirimycin, an inhibitor of glycoprotein processing.