Corchorusides A and B, new flavonol glycosides as α-glucosidase inhibitors from the leaves of Corchorus olitorius

LC-ESI-MS analysis, antioxidant, anti-diabetic and molecular docking studies on Corchorus depressus (L.) C.Chr

The present study encompasses the ethnomedicinal consumption of Corchorus depressus (L.) C.Chr. (C. depressus) for diabetes. Samples were subjected to LC-ESI-MS analyses. The n-hexane, methanolic and water extracts were screened for α-glucosidase inhibition and in vivo anti-diabetic studies. Further, antioxidant (DPPH) and anti-inflammatory study was performed via luminol-enhanced chemi-luminescence assay. The identified compounds were docked against the target enzymes of diabetes. The n-hexane fraction (CD-J1) showed IC50 of 8.4 ± 0.1 µg/mL against α-glucosidase enzyme. The sub fractions CD-12 and CD-13 of CD-J1 obtained after flash column chromatography displayed further reduced IC50 values of 4.3 ± 0.1 and 6.3 ± 0.1, respectively, as compared with standard drug acarbose (IC50 values of 37.5 ± 0.2 µg/mL). Simultaneously, dereplication of most active sub-fraction CD-12 by LC-ESI-MS led to the identification of strophanthidin and some other active metabolites responsible for anti-diabetic activity. Molecular docking of strophanthidin with α-glucosidase and α-amylase revealed high affinity for these target enzymes.

The Potential of Corchorus olitorius Seeds Buccal Films for Treatment of Recurrent Minor Aphthous Ulcerations in Human Volunteers

Aphthous ulcers are very common disorders among different age groups and are very noxious and painful. The incidence of aphthous ulcer recurrence is very high and it may even last for a maximum of 6 days and usually, patients cannot stand its pain. This study aims to prepare a buccoadhesive fast dissolving film containing Corchorus olitorius seed extract to treat recurrent minor aphthous ulceration (RMAU) in addition to clinical experiments on human volunteers. An excision wound model was used to assess the in vivo wound healing potential of Corchorus olitorius L. seed extract, with a focus on wound healing molecular targets such as TGF-, TNF-, and IL-1. In addition, metabolomic profiling using HR-LCMS for the crude extract of Corchorus olitorius seeds was explored. Moreover, molecular docking experiments were performed to elucidate the binding confirmation of the isolated compounds with three molecular targets (TNF-α, IL-1β, and GSK3). Additionally, the in vitro antioxidant potential of C. olitorius seed extract using both H2O2 and superoxide radical scavenging activity was examined. Clinical experiments on human volunteers revealed the efficiency of the prepared C. olitorius seeds buccal fast dissolving film (CoBFDF) in relieving pain and wound healing of RMAU. Moreover, the wound healing results revealed that C. olitorius seed extract enhanced wound closure rates (p ≤ 0.001), elevated TGF-β levels and significantly downregulated TNF-α and IL-1β in comparison to the Mebo-treated group. The phenotypical results were supported by biochemical and histopathological findings, while metabolomic profiling using HR-LCMS for the crude extract of Corchorus olitorius seeds yielded a total of 21 compounds belonging to diverse chemical classes. Finally, this study highlights the potential of C. olitorius seed extract in wound repair uncovering the most probable mechanisms of action using in silico analysis.

Protective effects on ovalbumin-induced mouse asthma models and qualitative and quantitative analysis of multiple compounds in Gerberae Piloselloidis Herba

Gerberae Piloselloidis Herba is widely used to treat cough and asthma in China. However, its effects on allergic asthma as related to its chemical compositions have not been fully elucidated, and there is a scarcity of methods to determine multi-component contents for quality control. In this study, protective effects of Gerberae Piloselloidis Herba on ovalbumin-induced asthma models were investigated, while qualitative and quantitative analyses of multiple constituents in Gerberae Piloselloidis Herba were conducted by using an ultrahigh-performance liquid chromatography -Q Exactive hybrid quadrupole-orbitrap high-resolution accurate mass spectrometry and an ultrahigh-performance liquid chromatography -photodiode array detection. The results showed that Gerberae Piloselloidis Herba could significantly mitigate asthma symptoms, reduce eosinophils counts in the bronchoalveolar lavage fluid, as well as decrease IgE, IL-5 and IL-13 concentration, and inflammatory cellular infiltration in lung tissues. A total of 51 compounds were tentatively identified, in which the content of 10 representative compounds was determined in 24 batches of Gerberae Piloselloidis Herba by using an ultrahigh-performance liquid chromatography method with good linearity, precision, repeatability, accuracy and stability. This research presents a comprehensive strategy combining biological activity evaluation with chemical profiling, providing a useful and comprehensive reference for further application and quality control of Gerberae Piloselloidis Herba. This article is protected by copyright. All rights reserved.

Dietary flavonoid aglycones and their glycosides: Which show better biological significance?

The dietary flavonoids, especially their glycosides, are the most vital phytochemicals in diets and are of great general interest due to their diverse bioactivity. The natural flavonoids almost all exist as their O-glycoside or C-glycoside forms in plants. In this review, we summarized the existing knowledge on the different biological benefits and pharmacokinetic behaviors between flavonoid aglycones and their glycosides. Due to various conclusions from different flavonoid types and health/disease conditions, it is very difficult to draw general or universally applicable comments regarding the impact of glycosylation on the biological benefits of flavonoids. It seems as though O-glycosylation generally reduces the bioactivity of these compounds - this has been observed for diverse properties including antioxidant activity, antidiabetes activity, anti-inflammation activity, antibacterial, antifungal activity, antitumor activity, anticoagulant activity, antiplatelet activity, antidegranulating activity, antitrypanosomal activity, influenza virus neuraminidase inhibition, aldehyde oxidase inhibition, immunomodulatory, and antitubercular activity. However, O-glycosylation can enhance certain types of biological benefits including anti-HIV activity, tyrosinase inhibition, antirotavirus activity, antistress activity, antiobesity activity, anticholinesterase potential, antiadipogenic activity, and antiallergic activity. However, there is a lack of data for most flavonoids, and their structures vary widely. There is also a profound lack of data on the impact of C-glycosylation on flavonoid biological benefits, although it has been demonstrated that in at least some cases C-glycosylation has positive effects on properties that may be useful in human healthcare such as antioxidant and antidiabetes activity. Furthermore, there is a lack of in vivo data that would make it possible to make broad generalizations concerning the influence of glycosylation on the benefits of flavonoids for human health. It is possible that the effects of glycosylation on flavonoid bioactivity in vitro may differ from that seen in vivo. With in vivo (oral) treatment, flavonoid glycosides showed similar or even higher antidiabetes, anti-inflammatory, antidegranulating, antistress, and antiallergic activity than their flavonoid aglycones. Flavonoid glycosides keep higher plasma levels and have a longer mean residence time than those of aglycones. We should pay more attention to in vivo benefits of flavonoid glycosides, especially C-glycosides.

Natural Flavonoids as Potential Herbal Medication for the Treatment of Diabetes Mellitus and its Complications

Diabetes mellitus, together with its various complications, is becoming a serious threat to human health. Natural products are secondary metabolites widely distributed in plants, having a broad range of biological activities. The development of antidiabetic medication from natural products, especially those originating from plants with a traceable folk-usage history in treating diabetes, is receiving more attention. Many studies highlighted not only the benefits of natural flavonoids with hypoglycemic effects, but also their importance in the management of diabetic complications. This review describes selected natural flavonoids that have been validated for their hypoglycemic properties, together with their mechanisms of action. Also discussed are their activities in the treatment of diabetic complications demonstrated via laboratory diabetic animal models, in vitro and clinical trials using human subjects. Published papers from 2000 to date on flavonoids and diabetes were covered through accessing Web of Science and multiple databases for biomedical sciences. The major potential benefits of natural flavonoids discussed in this review clearly suggest that these substances are lead compounds with sufficient structural diversity of great importance in the antidiabetic drug developing process.

The use of plants in the traditional management of diabetes in Nigeria: pharmacological and toxicological considerations

ETHNOPHARMACOLOGICAL RELEVANCE

The prevalence of diabetes is on a steady increase worldwide and it is now identified as one of the main threats to human health in the 21st century. In Nigeria, the use of herbal medicine alone or alongside prescription drugs for its management is quite common. We hereby carry out a review of medicinal plants traditionally used for diabetes management in Nigeria. Based on the available evidence on the species׳ pharmacology and safety, we highlight ways in which their therapeutic potential can be properly harnessed for possible integration into the country׳s healthcare system.

MATERIALS AND METHODS

Ethnobotanical information was obtained from a literature search of electronic databases such as Google Scholar, Pubmed and Scopus up to 2013 for publications on medicinal plants used in diabetes management, in which the place of use and/or sample collection was identified as Nigeria. 'Diabetes' and 'Nigeria' were used as keywords for the primary searches; and then 'Plant name - accepted or synonyms', 'Constituents', 'Drug interaction' and/or 'Toxicity' for the secondary searches.

RESULTS

The hypoglycemic effect of over a hundred out of the 115 plants reviewed in this paper is backed by preclinical experimental evidence, either in vivo or in vitro. One-third of the plants have been studied for their mechanism of action, while isolation of the bioactive constituent(s) has been accomplished for twenty three plants. Some plants showed specific organ toxicity, mostly nephrotoxic or hepatotoxic, with direct effects on the levels of some liver function enzymes. Twenty eight plants have been identified as in vitro modulators of P-glycoprotein and/or one or more of the cytochrome P450 enzymes, while eleven plants altered the levels of phase 2 metabolic enzymes, chiefly glutathione, with the potential to alter the pharmacokinetics of co-administered drugs.

CONCLUSION

This review, therefore, provides a useful resource to enable a thorough assessment of the profile of plants used in diabetes management so as to ensure a more rational use. By anticipating potential toxicities or possible herb-drug interactions, significant risks which would otherwise represent a burden on the country׳s healthcare system can be avoided.

WITHDRAWN: Flavonoid glycosylation and biological benefits

This article has been withdrawn at the request of the editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Orthosiphol A from the Aerial Parts of Orthosiphon aristatus is Putatively Responsible for Hypoglycemic Effect via α-Glucosidase Inhibition

An infusion of Orthosiphon aristatus has long been used for diabetes therapy; however, the active principles remained unknown. Herein, we report the identification of the putative agents responsible for this antidiabetic activity using an α-glucosidase-guided isolation. Four flavonoids named sinensetin (1), salvigenin (2), tetramethylscutellarein (3) and 3,7,4′-tri- O-methylkaempferol (4), together with a diterpenoid named orthosiphol A (5), were characterized, based on analysis of their spectroscopic data. Flavonoids 3 and 4 inhibited yeast α-glucosidase with IC50 values of 6.34 and 0.75 mM, respectively, whereas orthosiphol A (5) selectively inhibited intestinal maltase with an IC50 value of 6.54 mM. A kinetic investigation of 5 indicated that it retarded maltase function in a noncompetitive manner.

Advance in dietary polyphenols as α-glucosidases inhibitors: a review on structure-activity relationship aspect

The dietary polyphenols as α-glucosidases inhibitors have attracted great interest among researchers. The aim of this review is to give an overview of the research reports on the structure-activity relationship of dietary polyphenols inhibiting α-glucosidases. The molecular structures that influence the inhibition are the following: (1) The hydroxylation and galloylation of flavonoids including catechins improve the inhibitory activity. (2) The glycosylation of hyroxyl group and hydrogenation of the C2=C3 double bond on flavonoids weaken the inhibition. (3) However, cyaniding glycosides show higher inhibition against than cyanidin. Proanthocyanidins oligomers exhibit a stronger inhibitory activity than their polymers. (4) The hydroxylation on B ring and the glycosylation of stilbenes reduce the inhibitory activity. (5) Caffeoylquinic acids display strong inhibition against α-glucosidases. However, hydroxycinnamic acid, ferulic acid, and gallic acid hardly inhibited α-glucosidases. (6) The coupled galloyl structures attached to C-3 and C-6 of the 4C(1) glucose core of ellagitanin gave basic inhibitory activity. (7) The mono-glycosylation of chalcones slightly lowers the inhibition. However, the diglycosylation of chalcones significantly decreased the activity.

First Identification of α-Glucosidase Inhibitors from Okra (Abelmoschus Esculentus) Seeds

Infusion of roasted okra seeds has long been consumed in Turkey for diabetes mellitus therapy. Previous reports of a hypoglycemic effect observed in rats administrated with okra seed extract indicated a possible connection with inhibition of intestinal α-glucosidase. An attempt to identify active components was first herein conducted using α-glucosidase-inhibition-guided isolation, yielding two major flavonol glucosides named isoquercetin (2) and quercetin-3- O-β-glucopyranosyl-(1″′ →6″)-glucoside (3). They selectively inhibited rat intestinal maltase and sucrase, in which isoquercetin (2) was 6–10 times more potent than its related diglucoside 3. This result suggested that an increase in hydrophilicity by the additional glucose residue in 3 led to a significant decline in the inhibitory effect and raised the possible involvement of the free 3-OH in exerting the inhibition. Our postulation was evaluated by examining α-glucosidase inhibition of quercetin (1), and the aglycone of 2 and 3, whose 3-OH is free from any glucose moiety. Interestingly, 1 displayed a broad inhibitory effect toward rat intestinal and baker's yeast α-glucosidases, with improved potency. A kinetic study of 1 indicated that it inhibited maltase by two distinct mechanisms, in competitive ( K i 462 μM) and noncompetitive ( K i 2153 μM) manners, whereas the mechanism underlying the inhibition of sucrase was verified as being of a competitive behavior ( K i 218 μM).

(+)-Pinoresinol is a putative hypoglycemic agent in defatted sesame (Sesamum indicum) seeds though inhibiting α-glucosidase

Defatted sesame seeds have been reported for hypoglycemic effect in mice and T2DM women. An attempted to identify active components responsible for this effect was conducted using α-glucosidase-guided fractionation, resulting in the isolation of various lignans. Of compounds isolated, only (+)-pinoresinol showed inhibitory activity against rat intestinal maltase with an IC(50) value of 34.3 μM. The kinetic study indicated that enzymatic hydrolysis of maltose is inhibited by (+)-pinoresinol through competitive and noncompetitive manners. However, a lower dissociation constant (k(i) 288 M) of EI complex suggested that competitive inhibition is predominant over noncompetitive mode (k'(i) 1342 M).

Chemical Constituents of the Aerial Parts of Scutellaria lateriflora and their α-Glucosidase Inhibitory Activities

MeOH extracts of 37 herbs were tested in screening experiments for rat intestinal α-glucosidase. The MeOH extract of the aerial parts of Scutellaria lateriflora L. (Lamiaceae) significantly inhibited sucrase and maltase activities, using sucrose and maltase as the substrates. Enzyme inhibition guided-fractionation of the MeOH extract of S lateriflora resulted in the isolation of a new diterpene glucoside, deacetylajugarin-IV 18- O-β-D-glucopyranoside (1), along with 20 known phenolics (2-21). The structures of 1-21 were elucidated on the basis of MS and NMR data analyses. Baicalein (4) and baicalin (10), a glycoside of 4, showed moderate sucrase inhibitory activities at IC50 values of 14.9 and 36.3 μM, respectively, whereas luteolin (3), acteoside (16), leucosceptoside A (18), and isoacteoside (20) showed weak inhibitory activities at IC50 values of 811, 522, 727, and 443 μM, respectively. This is the first report on mammalian α-glucosidase inhibitory activities of S lateriflora extract and identification of the constituents responsible for the activities. Apigenin (2), luteolin (3), 6-methoxyluteolin 4'-methyl ether (6), isoscutellarin 8- O-β-D-glucuronide (7), luteolin 7- O-β-D-glucuronide (9), wogonin 7- O-β-D-glucuronide methyl ester (12), eriodictyol (13), naringenin (14), naringenin 7- O-β-D-glucuronide (15), jionoside D (17), leucosceptoside A (18), and (+)-syringaresinol 4'- O-β-D-glucopyranoside (21) were isolated from this plant for the first time. The inhibitory properties of S lateriflora extract against α-glucosidase provide a prospect for its antidiabetic usage.

Concise synthesis of (+)-conduritol F and inositol analogues from naturally available (+)-proto-quercitol and their glucosidase inhibitory activity

An effective synthesis of (+)-conduritol F, (+)-chiro- and (+)-epi-inositols from naturally available (+)-proto-quercitol is described. This synthetic method provides a concise synthesis of cyclitols in enantiomerically pure form. Of the synthesized cyclitols, (+)-conduritol F potently inhibits type I α-glucosidase with an IC(50) value of 86.1 μM, which is five times greater than the standard antidiabetic drug, acarbose.