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One new prenyl flavanone ( 1 ), (2 S )-8-prenyl-5,6-dihydroxy-7-methoxyflavanone, and one new diarylbutanol ( 2 ), (7' S )-3'-hydroxy-linderagatin-A, were isolated from the stem bark of Uvaria siamensis (Annonaceae), along with five known compounds, eriodictyol ( 3 ), quercetin ( 4 ), paprazine ( 5 ), N - trans -caffeoyltyramine ( 6 ), and N - trans -feruloyltyramine ( 7 ). Their structures were determined through extensive spectroscopic analyses and comparison with the literature. The α -glucosidase inhibitory potential of 1-7 was evaluated. Compound 6 showed the highest inhibitory activity against α -glucosidase and exhibited superior potency compared to the positive control, with an IC 50 value of 0.12  μ M.

A study was conducted to investigate the anti-diabetic and anti-urease potential of Osbeckia nutans leaves (ONL). Six compounds, i.e. quercetin-3-O-glucoside, myricetin, shikimic acid, catechin, trans-ferulic acid and luteolin were identified from the butanol sub-fraction, BE2 and the ethyl acetate sub-fraction, EA5 of ONL. BE2 inhibited α-glucosidase and Jack bean urease with IC 50 values of 0.036 μg/mL (437.46 μg/mL for acarbose) and 0.327 mg/mL (0.039 mg/mL for thiourea), respectively. In the glucose uptake experiment, BE2 (0.05 mg/mL) treatment resulted in a substantial increase in glucose uptake in free fatty acid (FFA)-treated cells at a concentration 10 times lower than that seen in EA5 (0.5 mg/mL) treated cells. The binding energies of quercetin-3-O-glucoside with α-glucosidase, glucose transporter GLUT4 and H. pylori urease were found to be -94.2585, -219.8271 and -254.391 kcal/mol, respectively. This study revealed that ONL has anti-diabetic and anti-urease abilities and further in-depth research may unveil its full potential.

Amomum dealbatum Roxb. parts have been traditionally used as remedies for joint pain, diabetes, muscular rheumatism, antiseptic, and abscesses in Arunachal Pradesh, Assam, and Tripura. Ethyl acetate sub-fraction E3 had significantly inhibited the α-glucosidase (IC 50 5.385 μg/mL). The molecular docking revealed quercetin-3-O-galactoside to be the most potent α-glucosidase inhibitor (binding energy -43.214 kcal/mol). Using the QSAR model, the pIC 50 values of myricetin, gallic acid, quercetin-3-O-galactoside, and acarbose were predicted to be 5.65235, 4.39858, 5.65235, and 6.03058, respectively. For the first time, quercetin-3-O-galactoside, myricetin, and gallic acid have been isolated from the flowers of A. dealbatum (ADF). E3 decreased blood glucose level to a near-normal concentration (100.60 ± 2.94 mg/dL) in comparison to diabetic control rats (575.20 ± 24.80 mg/dL). The results have strongly suggested the potential of ADF in treating diabetes. This lesser-known plant has the potential to uncover its full medicinal properties through further in-depth research.

In connection with our interest in the phytochemical investigation of Elaeocarpus hainanensis Oliv. (Elaeocarpaceae) growing in Vietnam, two new sulphated oleanane triterpenes were obtained herein and structurally identified. Based on the combination of the extensive 1D-, 2D NMR and HR ESI MS spectroscopic data analysis, their chemical structures have been elucidated as 1 α ,3 β -dihydroxy-olean-18-ene 1-sulphate ( 1 ) and 1 α ,3 β -dihydroxy-olean-12-ene 1-sulphate ( 2 ). Notably, compounds 1 and 2 are corroborating the proposition that triterpenoid sulphates serve as chemosystematic markers of the Elaeocarpus genus. Additionally, all these two new compounds 1 and 2 strongly inhibited α -glucosidase in vitro with the respective IC 50 values of 3.81 ± 0.33 µM and 21.27 ± 0.48 µM, which were significantly better than that obtained from positive control, acarbose (IC 50 247.73 ± 11.85 µM).

Phytochemical investigation of the stems of Bridelia stipularis led to the isolation of a new triterpene, 3 β - O - trans -feruloylfriedelinol ( 1 ), together with five known compounds, friedelin ( 2 ), 3 β -friedelinol ( 3 ), lupeol ( 4 ), stigmasterol ( 5 ), and 4-(1,5-dimethyl-3-oxo-4-hexenyl)benzoic acid ( 6 ). Their structures were identified by intensive spectroscopic analysis including 1D and 2D nuclear magnetic resonance, infrared, and mass spectrometry. Compound 1 showed significant α-glucosidase inhibitory activity (IC 50 = 337.49 ± 0.59 µM) close to the standard, acarbose. Furthermore, the structure activity relationship of 1 was analyzed by molecular docking studies. In addition, the molecular docking results showed that the interaction between 1 and the active site occurred through hydrophobic forces and hydrogen bonds.

Two new cyclic peptides, named as cyclogeobomptides A ( 1 ) and B ( 2 ) were isolated from the roots of Stachys geobombycis C. Y. Wu. Compounds 1 and 2 are both made up of eight amino acids. The structures of them were established on the basis of the spectral data, including mass spectrometry, 2D NMR, and X-ray crystallography. Cyclogeobomptides A and B were proved to have obvious inhibitory activities against α -glucosidase with the IC 50 values of 26.00 and 19.16  μ M, respectively.

Phytochemical investigation on the bark of E. kingiana plant afforded ten compounds, including six polyketides namely kingianin A 1 , kingianin B 2 , kingianin E 3 , kingianin F 4 , kingianin K 5 and kingianin L 6 , three endiandric acids; kingianic acid A 7 , tsangibeilin B 8 and endiandric acid M 9 , and one sesquiterpene; daibuoxide 10 . All compounds were separated as racemic mixture by recycling high-performance liquid chromatography (RHPLC), except for daibuoxide. Their structures were elucidated by detailed spectroscopic and comparative literature data analysis. This is the first report on the presence of the sesquiterpene; daibuoxide in Endiandra genus. In vitro enzymatic bio-evaluation of the isolated compounds against α -amylase and α -glucosidase showed that 4 demonstrated the best α -amylase and α -glucosidase inhibitory activity with IC 50 values of 181.54 ± 6.27 µg/mL and 237.87 ± 0.07 µg/mL, respectively. In addition, molecular docking analysis confirmed the α -amylase and α -glucosidase inhibitory activities demonstrated by 4 .

A new depsidone, parmoferone A ( 1 ), together with three known compounds, parmosidone K ( 2 ), albifolione ( 3 ), and 4-chloroorcinol ( 4 ) were isolated from the lichen Parmotrema cristiferum (Taylor) Hale (Parmeliaceae). The structures of isolated compounds were identified from its spectroscopic data and by comparison with the literature. Compounds 1-4 were evaluated for alpha-glucosidase inhibition. Compound 1 was determined to be a potent non-competitive inhibitor against alpha-glucosidase with an IC 50 value of 18.1 μM.

In our continuation of exploring antidiabetic agents from Garcinia species, we found that the methanolic extract of G. macrantha A.C.Sm. exhibited considerable α-glucosidase inhibition of 58.20 ± 0.37% in sucrose substrate and 39.86 ± 2.07% in maltose substrate at 100 μg/mL. Phytochemical investigation on the extract revealed the presence of a new biphenyl, macrabiphenyl A, which was successfully elucidated by means of spectroscopic methods (HRESIMS and 1D and 2D NMR). The α-glucosidase inhibitory evaluation indicated that the new compound was weakly active against the enzyme.

One new iridoid namely rupesin F ( 1 ) together with four known ones ( 2 - 5 ) were isolated from the roots of Valeriana jatamansi Jones. The structures were established using spectroscopic methods (1D and 2D NMR including HSQC, HMBC, COSY and NOESY) and by comparison with previously published literature data. The isolated compounds 1 and 3 exhibited strong α-glucosidase inhibition activity with IC 50 values of 10.13 ± 0.11 and 9.13 ± 0.03 μg/mL, respectively. This study enriched the chemical diversity of metabolites and provides a direction for the development of antidiabetic agents.

Viburnum luzonicum Rolfe is widely used in China as folk medicine. The bioactivity evaluation indicated that the n -BuOH fraction of V. luzonicum leaves (VLLB) could significantly inhibit α ‑amylase and α -glucosidase. In order to clarify its active constituents, the phytochemical analysis on VLLB was first performed using HPLC-QTOF-MS/MS, and three new phenolic compounds, viburosides A-C ( 1 - 3 ), along with seven known analogues ( 4 - 10 ) were isolated through preparative HPLC. The undescribed compounds were determined by extensive spectroscopic analyses ( 1 H and 13 C NMR, HSQC, HMBC, HRESIMS, and ORD) and enzymatic hydrolysis. In the in vitro enzyme assays, compounds 1 - 8 showed potent α ‑amylase and α -glucosidase inhibitory activities. The enzymatic kinetics and molecular docking of the strongest inhibitors 2 and 3 against the corresponding target enzyme were also performed.

From the EtOAc extract of the wood of the stems of Taxotrophis ilicifolius (Moraceae), two new secondary metabolites, named taxotrophises A ( 1 ) and B ( 2 ), were isolated, together with five known compounds ( 3 - 7 ). Their chemical structures have been elucidated by extensive NMR spectroscopic analysis. All isolated compounds have been evaluated for α -glucosidase inhibitory activity. In the present work, compounds 1 and 4 showed the strongest α -glucosidase inhibitory activity with IC 50 values of 6.5 and 1.5  μ M, respectively, and stronger than that of a positive control, acarbose (IC 50 ; 214.5  μ M).

Rehmannia glutinosa was extensively used to control blood sugar in diabetes treatment in tradition Chinese medicine. In the present study, three new compounds, including an iridoid rehmannia A ( 1 ) and two ionone rehmannias B-C ( 7-8 ), together with fourteen known compounds ( 2 - 6 and 9 - 17 ), were isolated from the roots of R. glutinosa . The structures of these compounds were determined by physicochemical constants and spectral analysis (1D, 2D-NMR and MS). The effect of 1-17 on α -glucosidase activity was tested in vitro . Compounds 9 , 10 , and 11 (IC 50 : 5.0, 3.1, and 6.3 mM) showed moderate activity to suppress α -glucosidase relative to acarbose (IC 50 = 3.0 mM). The findings provided some new insights to understand the hypoglycemic effect of R. glutinosa and the development towards the α -glucosidase inhibitor drugs.

Psidium guajava is a plant of the Myrtaceae with various pharmacological activity. In this study, the water extract and the isolated compounds from guava leaves were evaluated for in vitro α-glucosidase inhibition using spectrophotometric method. Ellagic acid, quercetin, quercetin-3-O-glucuronide, avicularin, isoquercitrin, and quercetin-3-galactoside showed α-glucosidase inhibitory activity, and their IC 50 value were 25.0, 41.0, 53.5, 46.9, 60.0 and 72.1 μg/mL, respectively compared with the positive control acarbose (IC 50 49.2 μg/mL). This study could provide a theoretical basis for the application of Psidium guajava in the treatment of hyperglycemia.

Two new phenolic allopyranosides, named viburluzosides A and B ( 1 , 2 ), together with eight known phenolic glycosides ( 3  -  10 ) were discovered from the stems of Viburnum luzonicum Rolfe under the guidance of LC-MS analyses coupled with bioactivity evaluation. They were purified through various chromatography methods and identified by extensive spectroscopic analyses ( 1 H and 13 C NMR, HSQC, HMBC, and HRESIMS) and chemical methods. The in vitro evaluation on α -glucosidase and aldose reductase (AR) inhibitory activities of isolated compounds were conducted. Compounds 1  -  4 and 6  -  9 exhibited α -glucosidase inhibitory activities with IC 50 values of 5.35 - 21.34 μM and AR inhibitory activities with IC 50 values of 6.21 - 40.06 μM. Moreover, the inhibitory kinetics analyses of compounds 1 and 2 were also performed.

Two new compounds geobomlin A ( 1 ) and geobomlin B ( 2 ) were isolated from the roots of Stachys geobombycis C. Y. Wu. Structural determinations were established principally by two-dimensional NMR and MS data analyses. Geobomlin B showed moderate inhibitory activity against α-glucosidase with IC 50 = 248.77 μM. We have also determined the mechanism by which geobomlin B elicit its inhibitory effect on α -glucosidase, for which we have established a competitive inhibition mode. Docking studies confirmed our results on geobomlin B α -glucosidase inhibitory properties.

A series of 24-ethylcholest-4-ene-3,6-dione 2 E -arylidene-derivatives has been synthesized by a Claisen-Schmidt reaction from a natural phytosterol β-sitosterol with yields of 80-85%. The structure of the obtained compounds was confirmed by NMR spectroscopy, including two-dimensional correlation experiments. The synthesized compounds were evaluated for their in vitro cytotoxicity and α-glucosidase inhibitory activity. It was established that compound 3 with pyridin-3-ylmethylene moiety exhibited a selective cytotoxic effect against the U251 cancer cell line with 99.31% inhibition of cancer cell growth. Compounds with pyridin-4-ylmethylene 4 and furan-2-ylmethylene -5 fragments were the most active inhibitors of α-glucosidase with IC 50 64.00 and 38.95 µM, being 3- and 5-times more active than acarbose. Binding mode to α-glucosidase and ADMET characteristics for the lead molecule 5 were proposed computationally. To sum up, an efficient approach to the derivatives with promising antidiabetic activity based on available natural product β-sitosterol is suggested.

A new cafestol-type diterpenoid, 5 β -hydroxy-2-oxocafestol named coffecanepholide C ( 1 ) along with three known diterpenoids including cafestol (2) , tricalysiolide A ( 3 ) and atractyligenin ( 4 ) were identified from the Coffea canephora trunks collected at Lam Dong province, Vietnam. Their structures were elucidated by HRESIMS and NMR spectroscopic analysis ( 1 H, 13 C, COSY, HSQC, HMBC, and NOESY NMR) as well as compared with data in the literature. Upon evaluation of the α -glucosidase inhibitory activity, compound 1 (IC 50 = 142.0 ± 0.2 µM) and compound 3 (IC 50 = 286.2 ± 1.2 µM) exhibited activity against α -glucosidase, while structures 2 and 4 showed no activity. Furthermore, the docking simulations revealed that the carbonyl groups of compounds 1 and 3 formed hydrogen bonds with Lys506 residue at the enzyme pocket, which may induce the α -glucosidase inhibitory activity.

Three new compounds ( 1 - 3 ), including two bisamide derivatives ( 1 and 2 ) and a lignin ( 3 ), along with 15 known compounds were isolated from Aglaia odorata. Compound 2 was a pair of enantiomers and successfully resolved into the anticipated enantiomers. Their structures were elucidated by extensive spectroscopic analysis, electronic circular dichroism (ECD) calculations, and X-ray crystallography. Three compounds showed excellent inhibitory activities on α -glucosidase with IC 50 values ranging from 54.48 to 240.88  μ M, better than that of the positive control (acarbose, IC 50 = 590.94  μ M). Moreover, compounds 3 , 13 , and 15 presented moderate inhibitory activities against butyrylcholinesterase. Compound 17 exhibited potent PTP1B inhibitory activity with an IC 50 value of 179.45 μM. Representative active compounds were performed for the molecular docking study. Herein, we described the isolation, structure elucidation, the inhibitory effects on three enzymes, and molecular docking of the isolates from the title plant.

The targeted identification of α-glucosidase inhibitors from the crude ethyl acetate of Lycopodiella cernua (L.) Pic. Serm ( L.cernua ) was guided by high-resolution inhibition profiling. The α-glucosidase inhibition profiling and HPLC-QTOF-MS showed tannins and serratenes were the corresponding antidiabetic constituents. Two new serratenes named 3β, 21β-dihydroxyserra-14-en-24-oic acid-3β-(4'-methoxy-5'-hydroxybenzoate) ( 4 ), 3β, 21α-dihydroxyserra-14-en-24-oic acid-3β-(4'-methoxy-5'-hydroxybenzoate) ( 7 ), together with two known compounds ( 5 and 6 ) were isolated. Their structures were elucidated by HR-ESI-MS and NMR. Compounds 5 - 7 inhibited the α-glucosidase activity in a non-competitive manner with Ki values ranging from 1.29 to 12.9 µM. The molecular docking result unveiled that 4 - 7 bound to the residues at the channel site, which enabled to block the substrate access. In addition, the molecular dynamics (MD) simulation of the most active compound 7 and α-glucosidase indicated the 4'-methoxy-5'-hydroxybenzoate group formed the stable hydrogen bonds and pi-pi T-shaped interactions with Arg312, Gln350 and Phe300 residues, while the rings D and E were stabilized by hydrophobic interaction.

Two new xanthones, oblongixanthones I ( 1 ) and J ( 2 ), and seven known compounds ( 3 - 9 ), were isolated from an EtOAc extract of the twigs of Garcinia oblongifolia . Their structures were elucidated using spectroscopic methods, mainly 1 D and 2 D NMR. The antidiabetic effects of the two new compounds were evaluated using α-glucosidase and PTP1B inhibition assays. Both compounds displayed strong inhibition towards α-glucosidase with IC 50 values of 258.7 ± 49.3 and 187.1 ± 27.5 μM, respectively (compared with acarbose, IC 50 = 900.0 ± 3.0 μM) and moderate effects against PTP1B with IC 50 values of 93.9 ± 12.3 and 64.1 ± 5.8 μM, respectively (compared with RK682, IC 50 = 4.4 ± 0.3 l μM).

A series of new phenyl acetylene and isoxazole analogues of arjunolic acid were designed, synthesized and evaluated (3 - 8 ) for their tyrosinase and alpha glucosidase inhibitory potential. All the tested analogues exhibited stronger inhibitory activity than the standard drug or parent compound. Of these, compound ( 7 ) displayed the most potent tyrosinase inhibitory action with IC 50 (14.3 ± 7.6) of about three folds more than the standard drug, kojic acid (41.5 ± 1.0). Further, compound ( 8 ) (14.5 ± 0.15) possessed the potent alpha glucosidase inhibitory action with IC 50 value comparable to that of standard, acarbose (10.4 ± 0.06). Henceforth, compounds ( 7 ) and ( 8 ) are promising candidates for further studies.

Nine compounds including a new one, garcichaudiic acid ( 1 ), were isolated from the bark of G. gaudichaudii and their structures were characterized mainly by 1 D and 2 D NMR experiments. The antioxidant capacity of the isolated compounds was determined using DPPH radical scavenging assay and the anti-hyperglycemic activity was assessed by measuring the inhibitory effect against α-glucosidase. Among them, compound 4 showed higher antioxidant activity than the positive control, ascorbic acid, while both compounds 1 and 7 exhibited more significant α-glucosidase inhibitory activity than the reference drug acarbose. Molecular docking analysis of the bioactive compounds was also performed to examine the binding modes and key interactions with the catalytic site.

Two new polyisoprenylated benzophenones, planchoniones A ( 1 ) and B ( 2 ), together with two known benzophenones ( 3, 4 ) and six known xanthones ( 5-10 ), were isolated from an ethyl acetate extract of the pericarp of Garcinia planchonii Pierre. Their structures were established using spectroscopic methods, mainly 1D and 2D NMR. The four benzophenones were evaluated for their cytotoxicity against MCF-7 human breast cancer cells, and showed almost no activity. Meanwhile, compounds 5 - 10 were investigated for their inhibitory effects towards α-glucosidase, and γ-mangostin (5) exhibited the most remarkable effect with IC 50 value of 15.3 ± 0.9 µM (compared with acarbose, IC 50 = 224.9 ± 3.6 µM).

A new glutinane-triterpenoid, nepetifoliol ( 1 ), together with two known compounds, dymacrin D ( 2 ), and (+)-ar-tumerone ( 3 ) were isolated from the n -hexane extract of the aerial parts of Leonotis nepetifolia . Their chemical structures were elucidated by spectroscopic data analysis as well as the comparison of their NMR data with the ones published in the literatures. A putative biosynthetic pathway for the formation of the new compound ( anti- diaxial-5,6-diol) ( 1 ) from the precursor triterpene glutinol was proposed. Compounds ( 2 ), ( 3 ) and some previously reported ones, isolated from this extract, including 5α-stigmasta-22-ene-3-one ( 4 ), friedelin ( 5 ), chrysophanol ( 6 ), physcion ( 7 ), and 4'- O -methylalpinumisoflavone ( 8 ) were evaluated for their α-glucosidase inhibition. Among tested compounds, 3 and 6 showed good activities with their IC 50 values of 5.3 ± 0.2 and 4.9 ± 0.3 µg/mL, respectively, comparing to the positive control, acarbose (IC 50 127.7 ± 0.2 µg/mL).

The study was aimed to investigate the phytochemical composition, antioxidant, antibacterial and enzyme inhibitory effects of Psydrax dicoccos leaf (PDL). Hydroalcoholic extract (HAE) was recorded with high concentration of total phenolics (59.68 ± 0.3 mg GAE/g), total flavonoids (57.85 ± 0.5 mgQRE/g) and proanthocyanidin (24.98 ± 0.17 mgAAE/g). Ethyl acetate (31.76 ± 1.52 mgQE/g), methanolic (34.99 ± 0.16 mgAAE/g) and aqueous (75.00 ± 0.30 mgGAE/g) extracts showed a high amount of total flavanols, vitamin E and total tannins, respectively. GC-MS analysis facilitated the identification of 56 metabolites with squalene and cinnamic acid as prominent compounds. HAE showed moderate α-amylase (IC 50 of 48.94 ± 0.5 µg/mL) and α-glucosidase (IC 50 of 46.98 ± 0.5 µg/mL) inhibitory activities. HAE is also perceived as a potent radical scavenger, reducing agent, metal chelating power, and total antioxidant capacity. For antibacterial activity, the aqueous extract was most effective with the MIC ranged from 87.5 to 175 µg/mL. Further characterization and in vivo studies are suggested to validate its traditional claim as a potential source of therapeutic agents.

The chalcone derivatives of 20-oxo-lupanes have been synthesised and screened for some types of biological activity. Ozonolysis of lupanes afforded 20-oxo-derivatives with the following condensation using different aromatic aldehydes by Claisen‒Schmidt reaction to the target compounds. The E configuration of 19-[3-(pyridin-3-yl)-prop-2-en-1-one]-fragment was established by X-ray analysis. Screening of cytotoxic activity against NCI-60 cancer cell line panel revealed, that messagenin derivative 9 has the highest activity with GI 50 value ranged from 0.304 to 0.804 μM. A colorimetric SRB assay revealed for the 2,30-bis-furfurylidene derivative 11 and 30-bromo-20-oxo-29-nor-3,28-diacetoxy-betulin 16 cytotoxic activity against breast carcinoma MCF-7 and ovarian carcinoma A2780 cell lines. Compounds 11 and 13 acted also as inhibitors of the enzyme α -glucosidase (from S. saccharomyces ) with IC 50 values of 1.76 μM and 3.3 μM thus being 97- and 52-fold more active than standard acarbose. Antiviral potency of compounds 12 and 14 against HCMV, HSV-1 and HPV is also discussed.[Formula: see text].

Termitomyces species are known edible mushrooms in Nigeria, believed to have exceptional culinary and nutraceutical properties. Methanol extract from fruiting bodies of Termitomyces robustus was evaluated for antidiabetic activity using in vitro α-amylase and α-glucosidase assays. The isolation and structural elucidation of metabolites from the T . robustus extract afforded five compounds including a new natural product γ-glutamyl-β-phenylethylamine 3 and four known phenyl derivatives: tryptophan 1 , 4-hydroxyphenylacetic acid 2 , 4-hydroxyphenylpropionic acid 4 , and phenyllactic acid 5 . Structures were elucidated from analyses of spectroscopic data (1   D and 2   D NMR, HRESIMS) and all isolated compounds were tested for α-amylase and α-glycosidase inhibitory activity. The in vitro assay established crude extract to possess α- amylase and α-glucosidase inhibition with IC 50 of 78.05   µg/mL and 86.10   µg/mL, respectively. The isolated compounds compared favourably with the standard drug, acarbose with IC 50 ranging from 6.18-15.08   µg/mL and 18.28-44.63   µg/mL for α-amylase and glucosidase, respectively.

Four flavonoid glycosides containing coumaroyl or feruloyl groups were isolated from the male flowers of Ginkgo biloba L., and compounds 3 and 4 were identified as novel compounds. The inhibitory activities against α-glucosidase were investigated by docking studies, in vitro assays and kinetic studies. The docking results showed that all compounds mainly formed hydrogen-bond and π-π-stacking interactions with α-glucosidase. Compound 4 had the lowest binding energy and maximum number of hydrogen bonds. Subsequently, the in vitro assays showed that compound 4 exhibited the strongest inhibitory potency. Finally, the kinetic studies indicated the inhibitory mode of compounds 1 - 4 against α-glucosidase were mixed types of competitive and non-competitive. Together, these findings suggested that the isolated flavonoid glycosides in this study, especially compound 4 , have potential as α-glucosidase inhibitors.

One new sesquiterpene dilactone, coccinine ( 1 ) and one new β -carboline alkaloid, daibucarboline F ( 2 ) together with 10 known compounds; linderane ( 3 ), linderalactone ( 4 ), pseudoneolinderane ( 5 ), linderanlide C ( 6 ), linderanine A ( 7 ), epicatechin ( 8 ), (-)-taxifolin ( 9 ), astilbin ( 10 ), L-quercitrin ( 11 ) and afzelin ( 12 ) were isolated from the stems and leaves of Neolitsea cassia (L.) Kosterm (Lauraceae). The structures of ( 1 and 2 ) were established by extensive spectroscopic methods and the known compounds were identified by comparisons with data reported in literature. The relative stereochemistry of compound ( 1 ) was assigned by X-ray diffraction analysis with Cu-K α irradiation. Compounds ( 3-8 ) and ( 10 ) were evaluated for their α -glucosidase enzymatic inhibitory activity. Compounds ( 4-6 ), ( 8 ) and ( 10 ) exhibited inhibition towards α -glucosidase enzymatic activity with IC 50 values ranging from 12.10 to 96.77 μM. This is the first report on the isolation of phytochemicals from N. cassia and their bioactivities.

Three new biflavonoids, umcephabiovins C - E ( 1 - 3 ), along with fourteen known compounds were isolated from the twigs and leaves of Cephalotaxus oliveri . Their structures and configurations were elucidated by UV, IR, NMR, ECD, and HR-ESI-MS spectra. Compounds 1 - 3 exhibited significant α -glucosidase inhibitory activity with IC 50 values of 7.05 ± 2.66, 24.45 ± 4.73, and 1.84 ± 1.14 μ M, respectively. Compound 11 showed moderate cytotoxicity against the BaF3/T315I cell line.

Amomum maximum Roxb. rhizome is a fork medicine mainly used in South and Southeast Asia. In present study, the hypoglycaemic effects of the ethanolic extract of A . maximum rhizome were demonstrated both on α-glucosidase assay in vitro and streptozotocin (STZ)-induced postprandial hyperglycaemia in mice. Furthermore, six labdane diterpenes, amoxanthin A (1), ottensinin (2), coronarin D (3), coronarin D methyl ether (4), isocoronarin D (5), and zerumin (6), were isolated from its ethyl acetate sub-fraction with the guidance of α-glucosidase inhibitory activity. Among these compounds, 2 and 6 exhibited significant inhibitory effect on α-glucosidase, as well as on STZ-induced high postprandial blood glucose levels in mice. Additionally, molecular docking analysis revealed that 2 and 6 could firmly bind to the active sites of α-glucosidase. These results suggest that compounds 2 and 6 are the main anti-hyperglycaemic agents present in A . maximum , which may demonstrate potential beneficial effects in diabetes management.

Five new phloroglucinol derivatives were isolated from Syzygium brachyantherum , and their structures were elucidated as brachyanones A-E ( 1-5 ) on the basis of the extensive spectroscopic analysis. Among them, compounds 1 and 3 exhibited significant inhibitory activity against α -glucosidase with IC 50 of 2.57 and 0.97  μ M, respectively. Furthermore, compound 4 showed protein tyrosine phosphatase 1B (PTP1B) inhibitory effect with inhibition ratio of 89.42% at 100  μ M. This discovery indicates that phloroglucinol derivatives with long aliphatic chain possibly play an important role in antidiabetic activity of Syzygium plants, and they could function as a promising antidiabetic agent.

The use of antidiabetic agents which control glycemic levels in the blood and simultaneously inhibit oxidative stress is an important strategy in the prevention of Diabetes Mellitus and its complications. In our previous study, malabaricone C ( 3 ) and its dimer, giganteone A ( 5 ) exhibited significant DPPH free radical scavenging activities which were lower than the activity of the positive control, ascorbic acid. These compounds were evaluated for their α-glucosidase inhibitory activities at different concentrations (0.02-2.5 mM) in the present study. Compounds 3 (IC 50 59.61 µM) and 5 (IC 50 39.52 µM) were identified as active alpha-glucosidase inhibitors, each respectively being 24 and 37 folds more potent than the standard inhibitor, acarbose. Based on the molecular docking studies, compounds 3 and 5 docked into the active site of the α-glucosidase enzyme, forming mainly hydrogen bonds in the active site.

1,2,3,4,6-Penta-O-galloyl-β-D-glucopyranose (β-PGG) is a compound commonly available in vegetables and fruits. It exhibited potential inhibition of α-glucosidase and hypoglycemic effect in vivo . This study explored its dynamics properties inhibiting α-glucosidase by Lineweaver - Burk plots, spectral analysis, docking analysis, and molecular dynamics simulations. β-PGG showed a mix-type inhibition when it was interacting with α-glucosidase. The fluorescence quenching indicated that the PGG-glucosidase complex formed in a spontaneous exothermic process and was driven by enthalpy. The synchronous fluorescence and ECD spectra indicate that β-PGG induced and changed the enzyme conformation in the complex formation. Docking results revealed multiple hydrogen bonds between the phenols and the amino acid residues. Further dynamic simulations indicated that the residues Asp345, Phe153, Arg435, Glu300, Pro305, and Phe296 played a more critical role in the interactions between β-PGG and α-glucosidase.

Although the cladodes of Nopalea cochenillifera are used in Mexican traditional medicine to treat diabetes and various other diseases, its antihyperglycaemic properties, phenolic content, and antioxidant activity are not well documented. Thus, we determined the activity of a single dose of fresh, blended cladodes on postprandial glycaemia in rats after a starch load. We prepared a methanolic extract of N. cochenillifera cladodes and measured its phenolic content, antioxidant capacity, and α-glucosidase inhibitory activity. The antihyperglycaemic effect of blended cladodes was similar to that of acarbose when considering the changes in glucose levels from baseline. Furthermore, the methanolic extract contained a considerable amount of phenolic compounds and exhibited antioxidant activity in the DPPH assay, but did not markedly inhibit α-glucosidase and had a low antioxidant effect in the ABTS test.

Twelve benzylidene derivatives, one Baeyer-Villiger oxidative, six imine derivatives were successfully designed and synthesised from phyllanthone. In the search for potential new anti-diabetic agents, phyllanthone along with its benzylidene and oxidation analogues were evaluated for enzyme inhibition against α -glucosidase. In the benzylidene series, most analogues displayed stronger activity than the mother compound. Compound 1c revealed the strongest activity, outperforming the acarbose positive control with an IC 50 value of 19.59 µM. Phyllanthone and its derivatives were then tested for cytotoxic activity against the K562 cell line. The imine analogues displayed the most powerful cytotoxic activity with 3c and 3d having IC 50 values of 57.55 and 68.02 µM, respectively.

A series of lupeol derivatives 2 , 2a-2f , 2a-2h , 3a-3e , and 4a-4b were designed, synthesised and evaluated for their α -glucosidase inhibitory and cytotoxic activities. Among synthetic derivatives, lupeol analogues 2b and 2e containing a benzylidene chain exhibited the best activity against α -glucosidase and superior to the positive agent with the IC 50 values of 29.4 ± 1.33 and 20.1 ± 0.91 μM, respectively. Lupeol analogues 2d and 3a showed weak cytotoxicity against K562 cell line with the IC 50 values of 76.6 ± 2.40 and 94.4 ± 1.51 μM, respectively.

Two new pregnane glycosides, gyminosides A and B ( 1 and 2 ) and three known, tinctoroside B ( 3 ), tinctoroside C ( 4 ), and gymnepregoside F ( 5 ) were isolated from the leaves of Gymnema inodorum (Lour.) Decne. Their structures were elucidated by physical and chemical methods and comparing with those reported in the literature. All these compounds were evaluated for α -glucosidase assay. Compound 5 exhibited the most anti α -glucosidase activity with inhibitory percentage of 63.7 ± 3.9% at the concentration of 200 μM. Compounds 1 - 4 showed moderate anti α -glucosidase activity with inhibitory percentage ranging from 40.0 to 52.1%.

The synthesis of the methyl glycyrrhetinate glycosides and inhibition of α-glucosidase were studied. The carboxyl group of glycyrrhetinic acid was methylated, and glucose and galactose were introduced into the hydroxyl group to obtain compounds 7 and 12 . Compound 1 , 2 , 7 , 12 and glycyrrhizic acid (GL) were evaluated for their inhibitory activities against α-glucosidase. As a result, Compound 1 , 2 , 7 , 12 and GL all showed significant α-glucosidase inhibitory activity and IC 50 values were 0.465, 1.352, 0.759, 0.687 and 2.085 mM, respectively, and acted as non-competitive inhibitors. The activity of the compound 2 , 7 , 12 was lower than compound 1 , but significantly higher than GL. Therefore, it was concluded that the change of structure in glycyrrhetinic acid by chemical modification had certain effect on bioactivity, and the change of carboxyl group, hydroxyl group and the type of monosaccharide introduced were the influencing factors.

Smilax china ( SC ) is a medicinal plant that has been traditionally used for a number of pathological disorders. In current study, its various fractions were assessed for radical scavenging, phenolic, flavonoid content and enzyme inhibition. The methanolic extract (MSC) of SC was subjected to fractionation using different solvents including n -hexane, benzene, chloroform, ethyl acetate and n -butanol. Results revealed that ethyl acetate fraction showed maximum phenolic (101.81 ± 0.13 mg GAE/g) and flavonoid (96.80 ± 0.39 mg QE/g) content with maximum radical scavenging potential (82.51 ± 0.18%, IC 50 =104.45 µg/ml) as well as urease (82.63 ± 0.79%), tyrosinase (81.30 ± 0.41%) and Butyrylcholinesterase (BChE) (62.47 ± 0.76%) inhibition at 0.5 mg/ml. Whereas, maximum α -Glucosidase (87.56 ± 0.13%) and Acetylcholinesterase (AChE) inhibition (82.34 ± 0.64%) was exhibited by n -hexane and benzene fractions, respectively. Present study has revealed the promising radical scavenging, phenolic, flavonoid and enzyme inhibitory potential of various fractions of SC extract. Thus, the study is a step forward towards evidence-based phyto-medicine.

A phytochemical study from Zinnia peruviana L. resulted in the isolation of a new elemene-type sesquiterpene lactone, zinaflorin VI ( 1 ), along with the known elemenolides 2-5 and the flavone onopordin ( 6 ). The structures of these compounds were determined by analysis of their spectroscopic data. The antibacterial activity of the γ -elemenolides 1 , 4 , and 5 was evaluated. The δ -elemenolide juniperin ( 7 ), previously isolated from Zinnia juniperifolia , was included in this assay. Compounds 1 and 7 were active against Bacillus subtilis and Staphylococcus aureus with MICs = 32 and 64  µ g/mL for compound 1 and MICs = 4 and 8  µ g/mL for compound 7 . The α -glucosidase inhibitory activity of compounds 1 , and 4-7 was evaluated, but none of these compounds was found to be active.

To find a potent α -glucosidase inhibitor, 24 tyrosol derivatives with different substituents located at the meta , ortho , or para position of the phenyl group have been synthesised via the Mitsunobu reaction, characterised by 1 H NMR, 13 C NMR, ESI-MS and IR and evaluated for inhibition. The derivatives possessed varying degrees of in vitro inhibitory activity against α -glucosidase and a relationship between the structure and activity was subsequently established for all compounds. Two of these compounds with substituents at the para position showed significant inhibitory effects surpassing that of the control standard acarbose. Molecular docking studies performed to better understand the binding interactions between the enzyme and the two most active compounds showed substantial binding within the active site of α -glucosidase. Taken together, these results indicate that the position of the substituent plays a crucial role in this inhibition and may facilitate the development of new α -glucosidase inhibitors.

Ten pentacyclic triterpenes ( 1 - 10 ) were isolated from Lavandula coronopifolia. We evaluated their α -glucosidase inhibitory activity, and found that the aglycones, 1 , 2 , 3 , 4, 7 and 10 showed superior IC 50 values to the positive control. In order to explain the structural requirements for α -glucosidase inhibitory activity, eleven derivatives were prepared, including one new compound, 2-formyl-(A)1-19 α -hydroxy-1-norursane-2, 12-dien-28-oic acid 10c . The results demonstrated that a free hydroxyl at ring-A and a free carboxylic group at position 28 are key structural features for the α-glucosidase inhibitory activity, also that an ursane skeleton is optimum for the activity. Additionally, enzyme kinetic analysis of pomolic acid 2 , the most potent compound, revealed that it inhibited α -glucosidase in a mixed-type manner. The molecular docking simulation validated this type of inhibition and highlighted the role of the C-3 hydroxyl and C-28 carboxylic groups in interaction with the enzyme in silico .

Promalabaricone B (PMB), an acylphenol was isolated from dichloromethane-soluble extract of the seeds of Myrisitica fatua Houtt. PMB exhibited significant inhibitory activity on α -glucosidase enzyme. The molecular docking and dynamics studies of PMB with human maltase-glucoamylase were performed. PMB exhibited an enhanced glucose uptake in L6 myotubes with 46.3% in 2.5  µ M. Encouraged with these results; we investigated the molecular mechanism of PMB through the upregulation of AMPK. The results revealed that PMB promoted the glucose uptake in myocytes by stimulating the translocation and expression of GLUT4. From this, it is clear that PMB can acts as a potential therapeutic option for diabetes treatment, and its hypoglycaemic effect may be mediated by AMPK upregulation and induction of GLUT4 translocation.

Morus nigra and Bauhinia variegata are used in the Egyptian folk medicine for their hypoglycemic effects. The standardized ethanolic extracts of both plants caused a significant decrease in fasting blood glucose level at two different doses (250 and 500 mg/kg) in streptozotocin-induced diabetic rats' model. Further, in vitro antioxidant activity and α-glucosidase inhibition assays were conducted as well as the measurement of insulin levels and the biomarkers for both liver and kidney functions in the treated animals. Beneficiary effects of BMLE and BVLE in the treatment of diabetes were found not to be limited to hypoglycemic effect but included preventing liver and kidney tissue damage that are associated with diabetes. A strong inhibition of the α-glucosidase enzyme by both extracts may be a contributing mechanism in the overall anti-diabetic effect that was observed. Further detailed study is needed in the future to explore the mechanism of action of both plants.

Using various chromatographic separations, four compounds, including one new steroid saponin named vernoamyoside E ( 1 ), were isolated from the leaves of the Vietnamese medicinal plant Vernonia amygdalina Delile (Asteraceae). Their structures were established by spectroscopic methods such as 1D- and 2D-NMR, HR-ESI-MS, and HPLC analysis. The inhibitory activities against α-glucosidase and α-amylase of the isolated compounds from V. amygdalina were reported for the first time. The results indicated that compound 1 significantly inhibited both against α-amylase and α-glucosidase activity.

The present study was designed to conduct the bioassay-guided isolation of possible bioactive compound(s) responsible for the antidiabetic action of Xylopia aethiopica (Dunal) A. Rich. fruit. The isolation of compound was guided by α-glycosidase and α-amylase inhibitory activities. Molecular docking with Autodock Vina was used to decipher the mode of interaction and binding affinity of the possible compound(s) with the selected enzymes. A pentacyclic triterpene, oleanolic acid (OA) was isolated from fruit and exhibited significantly ( p  < 0.05) lower IC 50 values (α-amylase: 89.02 ± 1.12 µM, α-glucosidase: 46.05 ± 0.25 µM) than other fractions and the acarbose. Interestingly, OA was found to bind to the α-amylase and α-glucosidase with minimum binding energy values of -0.9 and -1.2 kcal/mol respectively and none of the interactions involved hydrogen bond formation. Data of this study suggest that OA is responsible for the antidiabetic action of X. aethiopica fruit through the inhibition of α-amylase and α-glucosidase enzyme activities.

The dry powder of MC fruits was extracted by maceration, ultrasonication, liquid-liquid partition and soxhlation. The in vitro antidiabetic and antioxidant assays were used to screen extracts and fractions. Refluxed and liquid partitioned extracts were fractionated using petroleum ether and ethyl acetate and purified with the help of preparative HPLC to give 2 phytoconstituents M1 and M2 respectively. Compound M1 (1) was identified as charantin and Compound M2 (2) was identified as momordicinin using spectral studies. Momordicinin showed potent α-amylase inhibitory activity with IC 50 15.86μg/ml which was reported for the first time.

A new glucoside, 3-methoxy-4- O - β -D-glucopyranosyl-methyl benzoate, has been isolated from Lycium schweinfurthii along with five known compounds through bioactivity guided fractionation of the total plant methanolic extract towards α -glucosidase inhibitory activity. All the isolated compounds were tested for their inhibitory effect on α -glucosidase enzyme. As a result, four of them showed a potent inhibitory activity and thus constitute a therapeutic approach to decrease postprandial hyperglycemia in diabetic patients.