Inhibitory effects of oxyresveratrol and cyanomaclurin on adipogenesis of 3T3-L1 cells

Facile construction of dibenzodioxo[3.3.1]nonanes bearing spirocyclohexadienones via domino [4 + 2] cycloaddition/C(sp3)-H oxidative dehydrogenation coupling reactions

A novel palladium catalyzed homodimerization of ortho-hydroxyphenyl substituted p-QMs has been developed via [4 + 2] cycloaddition/oxidative dehydrogenation coupling domino reactions. An interesting palladium catalyzed intramolecular benzyl C-H oxidation dehydrogenation to form a transannular C(sp³)-O bond was found. This protocol provided an efficient method to construct various dibenzodioxo[3.3.1]nonanes bearing spirocyclohexadienones.

Secondary Metabolites in the Dendrobium heterocarpum Methanolic Extract and Their Impacts on Viability and Lipid Storage of 3T3-L1 Pre-Adipocytes

Although many natural products have proven their potential to regulate obesity through the modulation of adipocyte biology, none of them has yet been approved for clinical use in obesity therapy. This work aims to isolate valuable secondary metabolites from an orchid species (Dendrobium heterocarpum) and evaluate their possible roles in the growth and differentiation of 3T3-L1 pre-adipocytes. Six compounds were isolated from the orchid’s methanolic extracts and identified as amoenylin (1), methyl 3-(4-hydroxyphenyl) propionate (2), 3,4-dihydroxy-5,4’-dimethoxybibenzyl (3), dendrocandin B (4), dendrofalconerol A (5), and syringaresinol (6). Among these phytochemicals, compounds 2, 3, and 6 exhibited lower effects on the viability of 3T3-L1 cells, offering non-cytotoxic concentrations of ≲ 10 µM. Compared to others tested, compound 3 was responsible for the maximum reduction of lipid storage in 3T3-L1 adipocytes (IC₅₀ = 6.30 ± 0.10 µM). A set of protein expression studies unveiled that compound 3 at non-cytotoxic doses could suppress the expression of some key transcription factors in adipocyte differentiation (i.e., PPARγ and C/EBPα). Furthermore, this compound could deactivate some proteins involved in the MAPK pathways (i.e., JNK, ERK, and p38). Our findings prove that D. heterocarpum is a promising source to explore bioactive molecules capable of modulating adipocytic growth and development, which can potentially be assessed and innovated further as pharmaceutical products to defeat obesity.

Untapped Pharmaceutical Potential of 4,5,4'-Trihydroxy-3,3'-dimethoxybibenzyl for Regulating Obesity: A Cell-Based Study with a Focus on Terminal Differentiation in Adipogenesis

Obesity and its global prevalence has become a threat to human health, while its pharmacotherapy via the application of natural products is still underdeveloped. Here, we probed how 4,5,4'-trihydroxy-3,3'-dimethoxybibenzyl (TDB) derived from an orchid (Dendrobium ellipsophyllum) could exert its roles on the differentiation and function of murine (3T3-L1) and human (PCS-210-010) pre-adipocytes and offer some implications to modulate obesity. Cytotoxic effects of TDB on adipocytes were 2-fold lower than those detected with pre-adipocytes, and no significant difference was detected in cytotoxic profiles between both cell lineages. TDB in a dose-dependent manner decreased cellular lipid accumulation and enhanced lipolysis of both cell lines assessed at early differentiation and during maturation. Underlining molecular mechanisms proved that TBD paused the cell cycle progression by regulating inducers and inhibitors in mitotic clonal expansion, leading to growth arrest of pre-adipocytes at the G0/G1 phase. The compound also governed adipocyte differentiation by repressing expressions of crucial adipogenic regulators and effectors through deactivating the AKT/GSK-3β signaling pathway and activating the AMPK-ACC pathway. To this end, TDB has shown its pharmaceutical potential for modulating adipocyte development and function, and it would be a promising candidate for further assessments as a therapeutic agent to defeat obesity.

α-Glucosidase Inhibitory Activity and Anti-Adipogenic Effect of Compounds from Dendrobium delacourii

Chemical investigation of Dendrobium delacourii revealed 11 phenolic compounds, and the structures of these compounds were determined by analysis of their NMR and HR-ESI-MS data. All compounds were investigated for their α-glucosidase inhibitory activity and anti-adipogenic properties. Phoyunnanin E (10) and phoyunnanin C (11) showed the most potent α-glucosidase inhibition by comparing with acarbose, which was used as a positive control. Kinetic study revealed the non-competitive inhibitors against the enzyme. For anti-adipogenic activity, densifloral B (3) showed the strongest inhibition when compared with oxyresveratrol (positive control). In addition, densifloral B might be responsible for the inhibition of adipocyte differentiation via downregulating the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT enhancer-binding protein alpha (C/EBPα), which are major transcription factors in adipogenesis.

Role of stilbenes against insulin resistance: A review

Insulin resistance (IR) is a state characterized by the inability of tissues to utilize blood glucose particularly liver, muscle, and adipose tissues resulting in hyperglycemia and hyperinsulinemia. A close relationship exists between IR and the development of type 2 diabetes (T2D). Therefore, therapeutic approaches to treat IR also improve T2D simultaneously. Scientific evidence has highlighted the major role of inflammatory cytokines, reactive oxygen species (ROS), environmental & genetic factors, and auto-immune disorders in the pathophysiology of IR. Among therapeutic remedies, nutraceuticals like polyphenols are being used widely to ameliorate IR due to their safer nature compared to pharmaceutics. Stilbenes are considered important metabolically active polyphenols currently under the limelight of research to cope with IR. In this review, efforts are made to elucidate cellular and subcellular mechanisms influenced by stilbenes including modulating insulin signaling cascade, correcting glucose transport pathways, lowering postprandial glucose levels, and protecting β-cell damage and its effects on the hyperactive immune system and proinflammatory cytokines to attenuate IR. Furthermore, future directions to further the research in stilbenes as a strong candidate against IR are included so that concrete recommendation for their use in humans is made.

Oxyresveratrol: Sources, Productions, Biological Activities, Pharmacokinetics, and Delivery Systems

Oxyresveratrol has recently attracted much research attention due to its simple chemical structure and diverse therapeutic potentials. Previous reviews describe the chemistry and biological activities of this phytoalexin, but additional coverage and greater accessibility are still needed. The current review provides a more comprehensive summary, covering research from 1955 to the present year. Oxyresveratrol occurs in both gymnosperms and angiosperms. However, it has never been reported in plants in the subclass Sympetalae, and this point might be of both chemotaxonomic and biosynthetic importance. Oxyresveratrol can be easily obtained from plant materials by conventional methods, and several systems for both qualitative and quantitative analysis of oxyresveratrol contents in plant materials and plant products are available. Oxyresveratrol possesses diverse biological and pharmacological activities such as the inhibition of tyrosinase and melanogenesis, antioxidant and anti-inflammatory activities, and protective effects against neurological disorders and digestive ailments. However, the unfavorable pharmacokinetic properties of oxyresveratrol, including low water solubility and poor oral availability and stability, have posed challenges to its development as a useful therapeutic agent. Recently, several delivery systems have emerged, with promising outcomes that may improve chances for the clinical study of oxyresveratrol.

Mechanisms of action for the anti-obesogenic activities of phytochemicals

The prevalence of obesity is increasing rapidly globally and has recently reached pandemic proportions. It is a multifactorial disorder linked to a number of non-communicable diseases such as type-2 diabetes, cardiovascular disease, and cancer. Over-nutrition and a sedentary lifestyle are considered the most significant causes of obesity; a healthy lifestyle and behavioural interventions are the most powerful ways to achieve successful weight loss, but to maintain this in the long term can prove difficult for many individuals, without medical intervention. Various pharmacological anti-obesogenic drugs have been tested and marketed in the past and have been moderately successful in the management of obesity, but their adverse effects on human health often outweigh the benefits. Natural products from plants, either in the form of crude extracts or purified phytochemicals, have been shown to have anti-obesogenic properties and are generally considered as nontoxic and cost-effective compared to synthetic alternatives. These plant products combat obesity by targeting the various pathways and/or regulatory functions intricately linked to obesity. Their mechanisms of action include inhibition of pancreatic lipase activities, an increase in energy expenditure, appetite regulation, lipolytic effects, and inhibition of white adipose tissue development. In this review, we discuss the distinct anti-obesogenic properties of recently reported plant extracts and specific bioactive compounds, along with their molecular mechanisms of action. This review will provide a common platform for understanding the different causes of obesity and the possible approaches to using plant products in tackling this worldwide health issue.

Resveratrol and Oxyresveratrol Activate Thermogenesis via Different Transcriptional Coactivators in High-Fat Diet-Induced Obese Mice

Obesity is a global public health issue. Thermogenesis is a novel way to promote anti-obesity by consuming energy as heat rather than storing it as triacylglycerols. The browning program allows mitochondrial biosynthesis and thermogenesis-related gene expression to occur in subcutaneous white adipose tissue, which results in the formation of beige adipose tissue. Some phytochemicals have exerted the capability to activate the fat browning process. Resveratrol and oxyresveratrol are both natural stilbenoids that have been reported for their anti-obesity efficacy. However, the comparison between the two as they relate to thermogenesis as well as the differences in their underlying mechanisms are still not widely discussed. Our result reveals that both resveratrol and oxyresveratrol could elevate the expression of thermogenesis-related protein expression including UCP1 (uncoupling protein-1) and PRDM (PR domain containing 16) via Sirt1/PGC-1α (sirtuin 1/peroxisome proliferation gamma coactivator-1 α) activation. However, it is suggested that the transcriptional factor PPARα (peroxisome proliferator-activator receptor α) was activated by resveratrol (1.38 ± 0.07 fold) but not oxyresveratrol. Conversely, C/EBPβ (CCAAT/enhancer-binding protein β) was upregulated by oxyresveratrol (1.58 ± 0.05 fold) but not by resveratrol. On the other hand, CPT1 (carnitine palmitoyltransferase) was found to be significantly activated at lower concentrations of oxyresveratrol up to 1.89 ± 0.04 fold as compared to high-fat diet, and it could be a leading reason for UCP1 activation. Lastly, adiponectin expression was promoted in all experimental groups (1.53 ± 0.08 and 1.49 ± 0.11-fold in resveratrol (RES) and high oxyresveratrol (HOXY), respectively), which could be an activator for mitochondrial biosynthesis and UCP1 expression.

Toxic trans-crotonaldehyde in mitochondria intercepted by oxyresveratrol contributing to anticancer

The aim of this study was to explore how the toxic trans-crotonaldehyde (TCA) in mitochondria or aldehyde dehydrogenase (ALDH) at different pHs was intercepted by oxyresveratrol (Oxy-Res) contributing to anticancer. Ultraviolet-visible (UV-vis) spectroscopy and Raman spectroscopy were employed. UV-vis spectra showed that the Oxy-Res red shifted the peak of the toxic TCA from 316 nm to 325 nm, while the peaks of the Oxy-Res shifted from 329 nm with 290 nm and 300 nm to 325 nm with 303 nm. In the mitochondria, the Oxy-Res blue shifted the peaks of the toxic TCA from 325 nm with 303 nm to 321 nm with 301 nm. Raman spectra revealed that the Oxy-Res caused shifting of the CHO of the toxic TCA from 1,689 cm^-1 to 1,671 cm^-1 with band decline. The CC of the toxic TCA at 1641 cm^-1 was split into 1,639 cm^-1 and 1,642 cm^-1 with band decline. The bands of the Oxy-Res at 1634 cm^-1 , 1,617 cm^-1 , and 1,595 cm^-1 disappeared. In the mitochondria, the CC of the toxic TCA at 1641 cm^-1 splitting disappeared. In ALDH, with the decrease of pH from 7.8 to 6.5, the CHO of the toxic TCA did not red shift from 1,689 cm^-1 to 1,674 cm^-1 up to pH 6.5. There was no change in the CC of the toxic TCA at 1640 cm^-1 in ALDH at different pHs. The conclusion of the study was that the CHO of the toxic TCA was intercepted by the Oxy-Res under the action of ALDH in the mitochondria, particularly at pH 7.8. © 2019 IUBMB Life, 2019.

Intramolecular Benzannulation of 3-Sulfonyl-2-benzylchromen-4-ones: Synthesis of Sulfonyl Dibenzooxabicyclo[3.3.1]nonanes

In this work, a concise route for the synthesis of sulfonyl dibenzo-oxabicyclo[3.3.1]nonanes by a two-step route is described, including (i) NaBH₄/LiCl-mediated reduction of 3-sulfonyl-2-benzylchromen-4-ones and (ii) sequential BF₃·OEt₂-mediated intramolecular annulation of the resulting 3-sulfonyl-2-benzylchroman-4-ols. A plausible mechanism is proposed and discussed herein. This protocol provides a highly effective stereocontrolled aryl-hydroxyl Friedel-Crafts-type cross-coupling to construct the tetra- or pentacyclic bridged framework. The use of various reaction conditions is investigated for an efficient transformation.

Oxyresveratrol-induced DNA cleavage triggers apoptotic response in Candida albicans

Oxyresveratrol is a naturally occurring phytoalexin produced by plants in response to infection. Biological activities of oxyresveratrol have been studied such as antioxidant, anticancer and anti-inflammation. However, further antimicrobial activity and its mechanism need to be investigated. This study exhibited growth inhibition against pathogenic fungi and investigated its mode of action. Oxyresveratrol inflicted cleavage on DNA, leading to G2/M phase arrest. DNA damage by oxyresveratrol was not the result of oxidative stress but it was triggered by direct binding to DNA. Oxyresveratrol-treated cells showed an apoptotic pathway characterized by phosphatidylserine exposure, apoptotic volume decrease and metacaspase activation. Mitochondria-associated apoptotic features also appeared. Oxyresveratrol-induced Ca²⁺ overload led to mitochondrial membrane depolarization and release of cytochrome c from mitochondria to cytosol. In conclusion, oxyresveratrol with DNA-binding affinity induces DNA cleavage, and eventually leads to mitochondria-mediated apoptosis in Candida albicans.

Oxyresveratrol Supplementation to C57bl/6 Mice Fed with a High-Fat Diet Ameliorates Obesity-Associated Symptoms

Oxyresveratrol has been proven effective in inhibiting adipogenesis in a 3T3-L1 cell model. We investigated the preventive effect of oxyresveratrol supplementation on obesity development in high-fat diet-fed mice. Male C57bl/6 mice were randomly subjected to control (5% fat by weight, LF), high-fat (30% fat by weight, HF), and high-fat supplemented with 0.25% and 0.5% oxyresveratrol (OXY1 and OXY2, respectively) diet groups for eight weeks. Oxyresveratrol supplementation effectively alleviated obesity-associated symptoms such as insulin resistance, hyperglycemia, and hepatic steatosis in high-fat diet-fed mice. Compared to the high-fat diet group, oxyresveratrol supplementation suppressed expression of glucose-6-phosphatase, sterol regulatory element-binding proteins 1, fatty acid synthase and CCAAT/Enhancer-binding proteins α, and elevated AMP-activated protein kinase (α2-catalytic subunit) level in liver, upregulated insulin-dependent glucose transporter type 4 level in adipose tissue, and increased expression of insulin receptor substrate 1, insulin-dependent glucose transporter type 4, AMP-activated protein kinase α, peroxisome proliferator-activated receptor γ coactivator-1α, and sirtuin 1 in muscle to regulate lipid and glucose homeostasis in these tissues. This study demonstrated that oxyresveratrol supplementation effectively ameliorated obesity-associated symptoms in high-fat diet-fed mice, presumably attributed to mediating critical regulators involved in lipid and glucose homeostasis in liver, visceral fat, and muscle.

Screening of six Ayurvedic medicinal plants for anti-obesity potential: An investigation on bioactive constituents from Oroxylum indicum (L.) Kurz bark

ETHNOPHARMACOLOGICAL RELEVANCE

As an effort to identify newer anti-obesity lead(s) we have selected 13 plant materials from the six plant species which have been reported in Indian Ayurvedic medicine as remedy against complications affecting glucose and lipid homeostasis.

AIM OF THE STUDY

In vitro screening of six Indian Ayurvedic medicinal plants on anti-adipogenic and pancreatic lipase (PL) inhibition potential followed by bioactivity guided isolation from most active plant material.

MATERIALS AND METHODS

In vitro anti-adipogenic assay using 3T3-L1 preadipocytes and pancreatic lipase (PL) inhibition assay were performed for hexanes, dichloromethane, ethyl acetate and methanolic extracts of all the plant materials. Bioactivity guided isolation approach was used to identify active constituent for anti-adipogenesis and PL inhibition assay. Inhibition of lipid accumulation and adipogenic transcription factor was measured by oil Red 'O' staining and quantitative real-time PCR method respectively.

RESULTS

Ethyl acetate extract of Oroxylum indicum bark was found to be most active in screening of anti-adipogenesis (59.12±1.66% lipid accumulation as compared to control at 50μg/mL dose) and PL inhibition (89.12±6.87% PL inhibition at 250μg/mL dose) assays. Further, three bioactive flavonoids were isolated and identified as oroxylin A, chrysin and baicalein from O. indicum bark. Oroxylin A, chrysin, and baicalein were inhibited lipid accumulation in 3T3-L1 preadipocytes (75.00±5.76%, 70.21±4.23% and 77.21±5.49% lipid accumulation respectively in comparison to control at 50μM dose) and PL enzyme (69.86±2.96%, 52.08±2.14% and 45.06±2.42% PL inhibition respectively at 250μg/mL dose). In addition, oroxylin A and chrysin also inhibited PPARγ and C/EBPα, major adipogenic transcription factors, in 3T3L-1 preadipocytes during adipogenesis process at 50μM dose.

CONCLUSION

The present study augurs the anti-obesity potential of well practiced Ayurvedic herb O. indicum and its flavonoids.

Cellular models for the evaluation of the antiobesity effect of selected phytochemicals from food and herbs

Dietary phytochemicals from food and herbs have been studied for their health benefits for a long time. The incidence of obesity has seen an incredible increase worldwide. Although dieting, along with increased physical activity, seems an easy method in theory to manage obesity, it is hard to apply in real life. Obesity treatment drugs and surgery are not successful or targeted for everyone and can have significant side effects. This low rate of success is the major reason that the overweight as well as the pharmaceutical industry seek alternative methods, including phytochemicals. Therefore, more and more research has focused on the role of phytochemicals to alleviate lipid accumulation or enhance energy expenditure in adipocytes. This review discusses selected phytochemicals from food and herbs and their effects on adipogenesis, lipogenesis, lipolysis, oxidation of fatty acids, and browning in 3T3-L1 preadipocytes.