Oxindole and Benzoxazinone Alkaloids from the Seeds of Persea americana (Avocado) and Their SIRT1 Stimulatory Activity.

Persea americana Mill. (Lauraceae), commonly known as avocado, is a well-known food because of its nutrition and health benefits. The seeds of avocado are major byproducts, and thus their phytochemicals and bioactivities have been of interest for study. The chemical components of avocado seeds were investigated by using UPLC-qTOF-MS/MS-based molecular networking, resulting in the isolation of seven new oxindole alkaloids (1-7) and two new benzoxazinone alkaloids (8 and 9). The chemical structures of the isolated compounds were identified by the analysis of NMR data in combination with computational approaches, including NMR and ECD calculations. Bioactivities of the isolated compounds toward silent information regulation 2 homologue-1 (SIRT1) in HEK293 cells were assessed. The results showed that compound 1 had the most potent effect on SIRT1 activation with an elevated NAD+/NADH ratio with potential for further investigation as an anti-aging agent.

Chemical constituents with senolytic activity from the stems of Limacia scandens.

While screening senotherapeutics from natural products, seven undescribed chemicals, two syringylglycerol derivatives, two cyclopeptides, one tigliane analogue, and two chromone derivatives, as well as six known compounds were isolated from the stems of Limacia scandens. The structures of compounds were elucidated through spectroscopic data analysis, including 1D and 2D NMR, HRESIMS, and CD data. All compounds were tested in replicative senescent human dermal fibroblasts (HDFs) to determine their potential as senotherapeutic agents to specifically target senescent cells. One tigliane and two chromones derivatives showed senolytic activity, indicating that senescent cells were selectively removed. Especially, 2-{2-[(3'-O-ß-d-glucopyranosyl)phenyl]ethyl}chromone is expected to be a potential senotherapeutics by inducing HDF death, inhibiting the activity of senescence-associated ß-galactosidase (SA-ß-gal) and expressing senescence-associated secretory phenotype (SASP) factors.

Insulin-mimetic activity of 23-glycosyl oleanane triterpenoids isolated from Gymnema latifolium.

Chemical investigation of the plant Gymnema latifolium led to the isolation of seven undescribed 23-glycosyl oleanane triterpenoids, gymlatinosides GLF1-GLF7, and two known compounds, gymnemosides D and E. The structures of the isolated compounds were elucidated using diverse spectroscopic methods. The extract of G. latifolium and all isolated compounds significantly enhanced 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) uptake into 3T3-L1 adipocytes at 20 µM. Among them, gymlatinosides GLF2 and gymlatinosides GLF4 showed particularly potent stimulatory effects on glucose uptake in a dose-dependent manner. Further investigation revealed that gymlatinosides GLF2 at 20 µM upregulated the expression of phosphorylated AMPK (p-AMPK). The results suggested that gymlatinosides GLF2 may enhance glucose uptake via regulating the AMPK signaling pathway.

Heliciopsides A-E, Unusual Macrocyclic and Phenolic Glycosides from the Leaves of Heliciopsis terminalis and Their Stimulation of Glucose Uptake.

Ten phenolic constituents, including three new macrocyclic glycosides (1-3), a new phenolic glycoside (5), a new biphenyl glycoside (6), and five known compounds (4, 7-10), were isolated from a 70% MeOH extract of the leaves of Heliciopsis terminalis by liquid chromatography-tandem mass spectrometry (LC-MS/MS)-guided molecular networking. The chemical structures of new compounds 1-3, 5 and 6 were established based on comprehensive spectroscopic data analysis, including 1D and 2D NMR and HRESIMS techniques. All isolated compounds (1-10) were evaluated for their stimulation of glucose uptake in differentiated 3T3-L1 adipocytes using 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-d-glucose (2-NBDG) as a fluorescent glucose analog. Compounds 3, 6 and 8 showed stimulatory effects on the uptake of 2-NBDG in 3T3-L1 adipocyte cells. Among them, compounds 3 and 6 activated the AMPK signaling pathway in differentiated C2C12 myoblasts.

Benzylisoquinoline Alkaloids from the Stems of Limacia scandens and Their Potential as Autophagy Inhibitors.

Limacia scandens is traditionally used to treat depression and affective disorders in Malaysia. The chemical compositions have been reported to include bisbenzylisoquinoline and aporphine-type alkaloids in the genus Limacia Lour., but studies on the components of L. scandens have rarely been reported. Therefore, this study was conducted to determine new benzylisoquinoline alkaloid derivatives with autophagy regulation activity from this plant. Bioactivity-guided isolation was applied to various column chromatography methods using RP-18, Sephadex LH-20 open column chromatography, and preparative HPLC. The chemical structures of the isolated compounds were elucidated through spectroscopic data analysis, including NMR, HR-ESI-MS, and ECD data. In addition, isolated compounds were tested for autophagy-regulating activity in HEK293 cells expressing GFP-L3. Three new dimeric benzylisoquinoline alkaloids (1-3), one new 4-hydroxybenzoic acid-conjugated benzylisoquinoline alkaloid (4), and six known compounds (5-10) were isolated from the stems of L. scandens. All compounds (1-10) were screened for autophagy regulation in HEK293 cells stably expressing the GFP-LC3 plasmid. Among the isolated compounds, 1, 2, and 4 showed autophagic regulation activity that blocked the process of combining autophagosomes and lysosomes. They also inhibit the protein degradation process from the autolysosome as inhibitors of autophagy. Novel benzylisoquinoline alkaloids from L. scandens showed potent potency for the inhibition of autophagic flux. This study provides potential candidates for developing natural autophagy inhibitors for disease prevention and treatment.

Dammarane-type triterpenoids from Gynostemma compressum X. X. Chen & D. R. Liang (Cucurbitaceae) and their AMPK activation effect in 3T3-L1 cells.

Bioassay-guided fractionation of the 80% ethanol extract of Gynostemma compressum X. X. Chen & D. R. Liang (Cucurbitaceae) resulted in the isolation and identification of eight undescribed triterpenoids, gycomol VN1, gycomol VN2, and gycomosides VN1-6 from the bioactive n-butanol fraction. The structures of these compounds were elucidated by one- and two-dimensional nuclear magnetic resonance spectroscopy, high-resolution electrospray ionisation mass spectrometry, and chemical methods. All isolated compounds were evaluated for their 5'-adenosine monophosphate-activated protein kinase (AMPK) and acetyl-coenzyme A carboxylase (ACC) activation effects on 3T3-L1 cells. Importantly, gycomol VN2, gycomoside VN1, and gycomosides VN3-5 activated the phosphorylation of AMPK and its downstream substrate ACC in 3T3-L1 cells at a dose of 10 µM. These effects imply that the activation of AMPK and ACC by active compounds from G. compressum has considerable potential for the prevention of obesity and its related disorders by activating AMPK signaling pathways.

Flavonostilbenes Isolated from the Stems of Rhamnoneuron balansae as Potential SIRT1 Activators.

The cumulative effects of cell damage result in aging, which gradually decreases human function in various aspects and leads to multiple age-related chronic diseases. To overcome the adverse effects of aging, silent mating type information regulation 2 homologue (SIRT1) activators are promising bioactive compounds that mimic calorie restriction to improve quality of life and prevent aging. In this study, 11 new flavonostilbenes (1-11) and three known compounds (12-14) were purified from stems of Rhamnoneuron balansae. The structures of the new compounds were determined using extensive data from spectroscopic methods, including NMR and HRESIMS. Their absolute configurations were deduced by ECD calculations with coupling constant analysis. All of the isolated new compounds (1-11) were evaluated for their effects on SIRT1 deacetylase activity, the NAD+/NADH ratio, and the AMP-activated protein kinase activation level in cell-based assays. The results showed that rhamnoneuronal D (1) exhibits promising biological activity in several in vitro models related to SIRT1 and suggest it is a potential natural-product-based antiaging agent.

Triterpenoid saponins from the leaves and stems of Pericampylus glaucus and their insulin mimetic activities.

During an attempt to discover insulin mimetics, thirteen new triterpenoid saponins (1-13), including three phytolaccagenic acids (1, 2, and 12) and ten serjanic acids (3-11 and 13), as aglycones were isolated from a 70% ethanol extract of leaves and stems from Pericampylus glaucus. The chemical structures of compounds 1-13 were determined through spectroscopic data analysis, including NMR, IR, and HRESIMS. All isolated compounds (1-13) were evaluated using 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-d-glucose (2-NBDG) as a fluorescent-tagged glucose probe to determine their stimulatory effects on glucose uptake in differentiated 3 T3-L1 adipocyte cells. Consequently, four compounds (4, 7, 11, and 12) exhibited stimulatory effects on glucose uptake.

Triterpenoids from the genus Gynostemma: Chemistry and pharmacological activities.

ETHNOPHARMACOLOGICAL RELEVANCE: G. pentaphyllum, also known as Jiao-Gu-Lan, has been used traditionally as folk remedies for many diseases, including diabetes mellitus, metabolic syndrome, aging, and neurodegenerative diseases in China and some countries in East and Southeast Asia. It is considered as an "immortality herb" in Guizhou Province, because it was consumed regularly by the elderly native inhabitants. Other species of the same genus Gynostemma such as G. longipes and G. laxum have been used as alternatives to G. pentaphyllum in ethno-medicine in Vietnam and other Asian countries. AIM OF THE REVIEW: The review aims to summarize up-to-date study results on Gynostemma species, including traditional usage, phytochemical profile, pharmacological activities, and toxicological studies, in order to suggest future research orientation and therapeutic applications on acute and chronic diseases. MATERIALS AND METHODS: The relevant literature on the genus Gynostemma was gathered from secondary databases (Web of Science and PubMed), books, and official websites. The latest literature cited in this review was published in February 2020. RESULTS: The genus Gynostemma has been widely used in traditional medicine, mainly for treatment of diabetes, hypertension, obesity, and hepatosteatosis. To date, 328 dammarane-type saponins were isolated and structurally elucidated from Gynostemma species. Crude extracts, saponin-rich fractions (gypenosides), and pure compounds were reported to show a wide range of pharmacological activities in both in vitro and in vivo experiments. The most notable pharmacological effects were anti-cancer, cardioprotective, hepatoprotective, neuroprotective, anti-diabetic, anti-obesity, and anti-inflammatory activities. Toxicological studies were conducted only on G. pentaphyllum, showing that the plant extracts were relatively safe in both acute and long-term toxicity experiments at the given dosage while no toxicological studies were reported for the other species. CONCLUSIONS: The review summarizes current studies on traditional uses, phytochemistry, biological properties, and toxicology of medicinal Gynostemma species. Till now, the majority of publications still focused only on G. pentaphyllum. However, the promising preliminary data of other Gynostemma species indicated the research potential of this genus, both in phytochemical and pharmacological aspects. Furthermore, clinical data are required to evaluate the efficacy and undesired effects of crude extracts, standard saponin fractions, and pure compounds prepared from Gynostemma medicinal plants.

Phenolic Constituents of the Roots of Rhamnoneuron balansae with Senolytic Activity.

With the advent of senolytic agents capable of selectively removing senescent cells in old tissues, the perception of age-associated diseases has been changing from being an inevitable to a preventable phenomenon of human life. In the search for materials with senolytic activity from natural products, six new flavonostilbenes (1-6), three new phenylethylchromanones (7-9), three new phenylethylchromones (10-12), and four known compounds (13-16) were isolated from the roots of Rhamnoneuron balansae. The chemical structures of these isolated compounds were determined based on the interpretation of spectroscopic data, including 1D and 2D NMR, ECD, and HRMS. The absolute configuration of compound 1 was also determined by a Mosher ester analysis and ECD calculations. Compounds 6-8 were shown to selectively destroy senescent cells, and the promoter activity of p16INK4A, a representative senescence marker, was reduced significantly by compound 6. The present results suggest the potential activity of flavonostilbene and phenylethylchromanone skeletons from R. balansae as new senolytics.

Oleanane Triterpenoids from the Leaves of Gymnema inodorum and Their Insulin Mimetic Activities.

During an effort to find insulin mimetic compounds, the leaves of Gymnema inodorum were shown to have a stimulatory effect on glucose uptake in 3T3-L1 adipocyte cells. Bioassay-guided fractionation on a 70% ethanol extract of G. inodorum was applied to yield two new (1 and 2) and two known (8 and 9) oleanane triterpenoids with a methyl anthranilate moiety together with five further new oleanane triterpenoids (3-7). The chemical structures of all isolates were determined based on their spectroscopic data, including IR, UV, NMR, and mass spectrometric analysis. The isolated compounds (1-9) were determined for their stimulatory activities on glucose uptake in differentiated 3T3-L1 adipocyte cells using 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-d-glucose (2-NBDG) as a fluorescent-tagged glucose probe. Three compounds (3, 5, and 9) showed stimulatory effects on the uptake of 2-NBDG in 3T3-L1 adipocyte cells. Chemicals with a methyl anthranilate moiety have been considered as crucial contributors of flavor odor in foods, and quantitative analysis showed the content of compound 8 to be 0.90 ± 0.01 mg/g of the total extract. These results suggest that the leaves of G. inodorum have the potential to be used as an antidiabetic functional food or tea.

Oleanane hemiacetal glycosides from Gymnema latifolium and their inhibitory effects on protein tyrosine phosphatase 1B.

Gymnema sylvestre (Retz.) R. Br. ex Schult. has a long history to be used as an antidiabetic herbal medicine. Various varieties of G. sylvestre, have been studied intensively on their 3ß-hydroxy oleanane triterpenoid composition for hypoglycemic effects. It is also well-known that most species belonging to the same genus have similar chemical composition and biological activity. Thus, an extract of the Gymnema latifolium Wall. ex Wight, which showed considerable protein tyrosine phosphatase 1B (PTP1B) inhibitory activity (>70% inhibition at 30 µg/mL), was studied intensively. Extensive chemical investigation on the 70% EtOH of G. latifolium led to the isolation of four previously undescribed oleanane hemiacetal glycosides, gymlatinosides GL1-GL4, three previously undescribed oleanane glycosides, gymlatinosides GL5-GL7, and two known 3ß-hydroxy oleanane analogs. The structures of the previously undescribed compounds were elucidated using diverse spectroscopic methods. The hemiacetal structure of the glycoside portion was further elaborated precisely by HMBC and J resolved proton NMR. Gymlatinosides GL2 and GL3 showed considerable PTP1B inhibitory effect.

Development of a Building Block Strategy to Target the Classification, Identification, and Metabolite Profiling of Oleanane Triterpenoids in Gymnema sylvestre Using UHPLC-qTOF/MS.

The major class of bioactive metabolites in Gymnema sylvestre, a popular Ayurvedic medicinal plant for the treatment of diabetes mellitus, is oleanane triterpenoids. In this study, a targeted, biosynthesis-inspired approach using UHPLC-qTOF/MS was implemented to elucidate the whole chemical profile of this plant for the standardization of the Vietnamese G. sylvestre variety. The known compounds were first determined to identify the building blocks of the biosynthetic intermediates and the construction rules for synthesizing oleanane triterpenoids in the plant. These blocks were recombined to build a virtual library of all reasonable compounds consistent with the deduced construction rules. Various techniques, including relative mass defect filtering, multiple key ion analysis, mass fragmentation analysis, and comparison with standard references, were applied to determine the presence of these predicted compounds. Conventional isolation and structure elucidation of six of the new compounds were carried out to identify the new building blocks and validate the assignments. Consequently, 119 peaks were quickly assigned to oleanane triterpenoids, and among them, 77 peaks were predicted to be new compounds based on their molecular formulas and mass fragmentation patterns. All the identified metabolites were then classified into different layers to analyze their logical relationships, and a multilayered chemical profile of the oleanane triterpenoids was constructed. This new approach is expected to be practical for characterizing structures of modular secondary metabolites, such as triterpenoid saponins, and for proposing biosynthetic relationships among compounds of the same class of metabolites in medicinal plants.

Constituents of the Edible Leaves of Melicope pteleifolia with Potential Analgesic Activity.

Melicope pteleifolia has long been consumed as a popular vegetable and tea in Southeast Asian countries, including Malaysia and southern mainland China, and is effective in the treatment of colds and inflammation. In the search for active metabolites that can explain its traditional use as an antipyretic, six new phloroacetophenone derivatives (3-8) along with seven known compounds (1, 2, and 9-13) were isolated from the leaves of M. pteleifolia. Their chemical structures were confirmed by extensive spectroscopic analysis including NMR, IR, ECD, and HRMS. All compounds isolated from the leaves of M. pteleifolia (1-13) have a phloroacetophenone skeleton. Notably, the new compound 8 contains an additional cyclobutane moiety in its structure. The bioactivities of the isolated compounds were evaluated, and compounds 1, 6, and 7 inhibited tumor necrosis factor-α-induced prostaglandin E2. Moreover, the major constituent, 3,5-di-C-ß-d-glucopyranosyl phloroacetophenone (1), was found to be responsible for the antipyretic activity of M. pteleifolia based on in vivo experiments.

Prenylated Phenolic Compounds from the Leaves of Sabia limoniacea and Their Antiviral Activities against Porcine Epidemic Diarrhea Virus.

Porcine epidemic diarrhea virus (PEDV), a serious swine epidemic, has been rampant in Asia since the 1990s. Despite the widespread use of PEDV vaccines, the occurrence of PEDV variants requires the discovery of new substances that inhibit these viruses. During a search for PEDV inhibitory materials from natural sources, seven new sabphenosides (1-7) and a new flavonoid (8), as well as eight known phenolic compounds (9-16), were obtained from the leaves of Sabia limoniacea. The structural determination of the new phenolic derivatives (1-8) was accomplished using comprehensive spectroscopic methods. Their absolute configurations were assigned by a combination of the ECD exciton chirality method following selective reduction and calculation of their ECD spectra. The bioactivities of the isolated compounds were measured based on their abilities to inhibit viral replication of PEDV. Among the test compounds, 15 and 16 exhibited the most promising antiviral activities, with IC50 values of 7.5 ± 0.7 µM and 8.0 ± 2.5 µM against PEDV replication. This study suggests that compounds 15 and 16 could serve as new scaffolds for the treatment of PEDV infection through the inhibition of PEDV replication.

Dereplication by High-Performance Liquid Chromatography (HPLC) with Quadrupole-Time-of-Flight Mass Spectroscopy (qTOF-MS) and Antiviral Activities of Phlorotannins from Ecklonia cava.

Ecklonia cava is edible seaweed that is found in Asian countries, such as Japan and Korea; and, its major components include fucoidan and phlorotannins. Phlorotannins that are isolated from E. cava are well-known to have an antioxidant effect and strong antiviral activity against porcine epidemic diarrhea virus (PEDV), which has a high mortality rate in piglets. In this study, the bioactive components were determined based on two different approaches: (i) bio-guided isolation using the antiviral activity against the H1N1 viral strain, which is a representative influenza virus that originates from swine and (ii) high-resolution mass spectrometry-based dereplication, including relative mass defects (RMDs) and HPLC-qTOFMS fragmentation analysis. The EC70 fraction showed the strongest antiviral activity and contained thirteen phlorotannins, which were predicted by dereplication. Ten compounds were directly isolated from E. cava extract and then identified. Moreover, the dereplication method allowed for the discovery of two new phlorotannins. The structures of these two isolated compounds were elucidated using NMR techniques and HPLC-qTOFMS fragmentation analysis. In addition, molecular modelling was applied to determine the absolute configurations of the two new compounds. The antiviral activities of seven major phlorotannins in active fraction were evaluated against two influenza A viral strains (H1N1 and H9N2). Six of the compounds showed moderate to strong effects on both of the viruses and phlorofucofuroeckol A (12), which showed an EC50 value of 13.48 ± 1.93 µM, is a potential active antiviral component of E. cava.

12,23-Dione dammarane triterpenes from Gynostemma longipes and their muscle cell proliferation activities via activation of the AMPK pathway.

The aging population is growing rapidly around the world and there is also an increase in sarcopenia, which is characterized by decreased muscle mass, strength and function in the elderly population. AMP-activated protein kinase (AMPK) is an essential sensor and regulator of glucose, lipid and energy metabolism throughout the body. Previous studies have shown that AMPK pathway activation by regular exercise and appropriate dietary control have beneficial effects on skeletal muscle. In the process of searching for new AMPK activators from medicinal plants, we isolated and characterized eight new 12,23-dione dammarane triterpenoids (1-3 and 5-9), as well as one known gypentonoside A from Gynostemma longipes. When all isolates were tested for their AMPK activation activities, seven compounds (1 and 3-8) were significantly activated AMPK phosphorylation in mouse C2C12 skeletal muscle cell lines. Since G. longipes contained a significant amount of active compound 1 (over 2.08% per dried raw plant), it suggested the potential of this plant to be developed as a functional food or botanical drug that enhances muscle proliferation by activating AMPK signaling pathways.

Hydroxyoleoside-type seco-iridoids from Symplocos cochinchinensis and their insulin mimetic activity.

As part of an ongoing study of new insulin mimetic agents from medicinal plants, the 70% EtOH extract of Symplocos cochinchinensis was found to have a stimulatory effect on glucose uptake in 3T3-L1 adipocyte cells. The intensive targeted isolation of this active extract resulted in ten new hydroxyoleoside-type compounds conjugated with a phenolic acid and monoterpene (1-6 and 8-11), as well as four known compounds (7 and 12-14). The chemical structures of the new compounds were determined based on spectroscopic data analysis (1H and 13C NMR, HSQC, HMBC, NOESY and MS). The absolute configurations of the isolated compounds were determined by electronic circular dichroism (ECD) analysis of derivatives obtained after a series of reactions, such as those with dirhodium (ІІ) tetrakis (trifluoroacetate) and dimolybdenum (ІІ) tetraacetate. In vitro, compounds 3, 7 and 8 moderately increased the 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-D-glucose (2-NBDG) uptake level in differentiated 3T3-L1 adipocytes. For further studies, we evaluated their effects on the expression of glucose transporter-4 (GLUT4), its translocation, protein tyrosine phosphatase 1B (PTP1B) inhibition and expression of phosphorylated Akt. Our results strongly suggest that the traditional uses of this plant can be described as active constituents by hydroxyoleoside-type compounds.

Flavone glycosides from Sicyos angulatus and their inhibitory effects on hepatic lipid accumulation.

A library of extracted natural materials (Korea Bioactive Natural Material Bank) have been screened to discover candidates for the treatment of non-alcoholic liver disease (NAFLD), and the 70% ethanol extract of Sicyos angulatus was found to inhibit hepatic lipid accumulation. Bioassay-guided fractionation of this bioactive extract yielded five previously undescribed flavonoid glycosides and one previously undescribed flavonolignan glycoside along with seven known flavonoid glycosides. The chemical structures of these compounds were elucidated by a combination of extensive spectroscopic analysis, including MS, NMR and UV techniques. Eight compounds of all isolated compounds showed inhibitory effects on the lipid accumulation induced by high concentrations of palmitic acid and glucose in HepG2 cells. Four selected compounds were tested for lipid content in a dose-dependent manner (10, 20 and 40 µM), and among those compounds, kaempferol 3-O-ß-d-glucopyranosyl-7-O-α-l-rhamnopyranoside showed the strongest inhibition of hepatic lipid production in HepG2 cells. In an oil-red O staining assay, five compounds were shown to reduce hepatic lipid accumulation better than what was observed in the vehicle control group. The present study suggests a new class of chemical entities for developing bioactive agents for the treatment of diseases caused by fat accumulation in the liver.

Insulin Mimetic Activity of 3,4- Seco and Hexanordammarane Triterpenoids Isolated from Gynostemma longipes.

As part of ongoing research to find new antidiabetic agents from medicinal plants, the chemical composition of Gynostemma longipes, an ethnomedicinal plant used to treat type 2 diabetes mellitus by local communities in Vietnam, was investigated. Ten new dammarane triterpenes, including two 3,4- seco-dammarane analogues, secolongipegenins S1 and S2 (1 and 2), a 3,4- seco-hexanordammarane, secolongipegenin S3 (3), two hexanordammarane glycosides, longipenosides ND1 and ND2 (4 and 5), and five other dammarane glycosides, longipenosides GL1-GL5 (6-10), were isolated from a 70% EtOH extract of the whole G. longipes plant. The structures of the new compounds were elucidated using diverse spectroscopic methods. All of the isolates were evaluated for their stimulatory activities on glucose uptake in differentiated 3T3-L1 adipocyte cells using 2-[ N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxy-d-glucose as a fluorescent-tagged glucose probe. The stimulant activities on glucose uptake by the test compounds were mediated via the activation of the AMPK pathway using differentiated mouse C2C12 skeletal myoblasts. Consequently, compounds 1, 2, and 4 enhanced glucose uptake and GLUT4 translocation significantly by regulating the AMPK signaling pathway.