The latest review on the polyphenols and their bioactivities of Chinese Morus plants

Structural optimization of Moracin M as novel selective phosphodiesterase 4 inhibitors for the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and high mortality lung disease. Although the antifibrotic drugs pirfenidone and nintedanib could slow the rate of lung function decline, the usual course of the condition is inexorably to respiratory failure and death. Therefore, new approaches and novel therapeutic drugs for the treatment of IPF are urgently needed. And the selective PDE4 inhibitor has in vivo and in vitro anti-fibrotic effects in IPF models. But the clinical application of most PDE4 inhibitors are limited by their unexpected and severe side effects such as nausea, vomiting, and diarrhea. Herein, structure-based optimizations of the natural product Moracin M resulted in a novel a novel series of 2-arylbenzofurans as potent PDE4 inhibitors. The most potent inhibitor L13 has an IC50 of 36 ± 7 nM with remarkable selectivity across the PDE families and administration of L13·citrate (10.0 mg/kg) exhibited comparable anti-pulmonary fibrosis effects to pirfenidone (300 mg/kg) in a bleomycin-induced IPF mice model, indicate that L13 is a potential lead for the treatment of IPF.

A dual recognition-based strategy employing Ni-modified metal-organic framework for in situ screening of SIRT1 inhibitors from Chinese herbs

Sirtuin1 (SIRT1), an NAD+-dependent histone deacetylase, plays a crucial role in regulating molecular signaling pathways. Recently, inhibition of SIRT1 rather than its activation shows the therapeutic potential for central nervous system disorder, however, the discovered SIRT1 inhibitors remains limited. In this work, a dual recognition-based strategy was developed to screen SIRT1 inhibitors from natural resources in situ. This approach utilized a Ni-modified metal-organic framework (Ni@Tyr@UiO-66-NH2) along with cell lysate containing an engineered His-tagged SIRT1 protein, eliminating the need for purified proteins, pure compounds, and protein immobilization. The high-performance Ni@Tyr@UiO-66-NH2 was synthesized by modifying the surface of UiO-66-NH2 with Ni2+ ions to specifically capture His-tagged SIRT1 while persevering its enzyme activity. By employing dual recognition, in which Ni@Tyr@UiO-66-NH2 recognized SIRT1 and SIRT1 recognized its ligands, the process of identifying SIRT1 inhibitors from complex matrix was vastly streamlined. The developed method allowed the efficient discovery of 16 natural SIRT1 inhibitors from Chinese herbs. Among them, 6 compounds were fully characterized, and suffruticosol A was found to have an excellent IC50 value of 0.95 ± 0.12 μM. Overall, an innovative dual recognition-based strategy was proposed to efficiently identify SIRT1 inhibitors in this study, offering scientific clues for the development of drugs targeting CNS disorders.

Morushalunin D, a tri-O-bridged Diels-Alder type adduct from Morus alba var. shalun root cultures and the related precursors

Three Diels-Alder type adducts (1-3) along with their precursors, including one 2-arylbenzofuran (4) and one stilbene (5), were isolated from the MeOH extract of M. alba var. shalun root cultures. Among them, 1 is a new Diels-Alder type adduct named morushalunin D. The molecular structures of 1-5 were elucidated based on spectroscopic data and comparison with the literatures. Cytotoxic properties of compounds 1-5 were evaluated against murine leukemia P-388 cells. Morushalunin D (1), mulberrofuran T (2), sorocein A (3), moracin M (4), and oxyresveratrol (5) were active, significantly inhibiting the growth of P-388 cells with IC50 values of 0.5, 1.0, 0.6, 2.0, and 3.3 μg/ml, respectively.

New indole alkaloid Morucolletotricin from endophytic fungus Colletotrichum queenslandicum associated with Morus australis Poir. Leaf

Six compounds were isolated from the ethyl acetate extract of endophytic fungus Colletotrichum queenslandicum derived from Morus australis Poir. leaf. Based on NMR and MS data led to characterised of these compounds including one new indole alkaloid Morucolletotricin (1) along with two other indole alkaloids; tryptopol (2) and indole-3-acetic acid (3), phomopyronol (4), 2-(3-aminophenyl)acetic acid (5) and ergosterol (6). phomopyronol (4) and 2-(3-aminophenyl)acetic acid (5) were first reported from Colletotrichum fungi. The cytotoxic activity of compounds 1-6 was evaluated against murine leukaemia P-388 cells and showed that all compounds were moderate cytotoxic. phomopyronol (4) was the most active among the five other compounds with IC50 = 37.17 μg/mL.

Prokinetic Activity of Mulberry Fruit, Morus alba L

The fruit of Morus alba L. (MAF) has been consumed as a food worldwide. MAF has also been widely used in traditional medicine for thousands of years in East Asia, and its diverse bioactivities have been reported in numerous publications. However, no prokinetic activity has been reported for MAF or its components. In the present study, therefore, we investigated the effects of MAF on gastrointestinal motor function by measuring the intestinal transit rate (ITR) of Evans blue in mice in vivo. The ITR values accelerated by MAF were significantly higher than those accelerated by cisapride or metoclopramide, suggesting that MAF has potential as a new prokinetic agent to replace cisapride and metoclopramide. We also investigated the effects of MAF on myogenic and neurogenic contractions in human intestinal smooth muscles by measuring spontaneous contractions of smooth muscle strips, smooth muscle contractions induced by neural stimulation, and migrating motor complexes from intestinal segments in the human ileum and sigmoid colon in situ. MAF increased both myogenic and neurogenic contractions to enhance ileal and colonic motility in the human intestine. Taken together, these results indicate that MAF enhanced intestinal motility by increasing both myogenic and neurogenic contractions, thereby accelerating the ITR.

An Arylbenzofuran, Stilbene Dimers, and Prenylated Diels–Alder Adducts as Potent Diabetic Inhibitors from Morus bombycis Leaves

Morus bombycis has a long history of usage as a treatment for metabolic diseases, especially, diabetes mellitus (DM). Thus, we aimed to isolate and evaluate bioactive constituents derived from M. bombycis leaves for the treatment of DM. According to bioassay-guided isolation by column chromatography, eight compounds were obtained from M. bombycis leaves: two phenolic compounds, p-coumaric acid (1) and chlorogenic acid methyl ester (2), one stilbene, oxyresveratrol (3), two stilbene dimers, macrourin B (4) and austrafuran C (6), one 2-arylbenzofuran, moracin M (5), and two Diels–Alder type adducts, mulberrofuran F (7) and chalcomoracin (8). Among the eight isolated compounds, the anti-DM activity of 3–8 (which possess chemotaxonomic significance in Morus species) was evaluated by inhibition of α-glucosidase, protein tyrosine phosphatase 1B (PTP1B), human recombinant aldose reductase (HRAR), and advanced glycation end-product (AGE) formation as well as by scavenging peroxynitrite (ONOO−), which are crucial therapeutic targets of DM and its complications. Compounds 4 and 6–8 significantly inhibited α-glucosidase, PTP1B, and HRAR enzymes with mixed-type and non-competitive-type inhibition modes. Furthermore, the four compounds had low negative binding energies in both enzymes according to molecular docking simulation, and compounds 3–8 exhibited strong antioxidant capacity by inhibiting AGE formation and ONOO− scavenging. Overall results suggested that the most active stilbene-dimer-type compounds (4 and 6) along with Diels–Alder type adducts (7 and 8) could be promising therapeutic and preventive resources against DM and have the potential to be used as antioxidants, anti-diabetic agents, and anti-diabetic complication agents.

Elicitation of Stilbenes and Benzofuran Derivatives in Hairy Root Cultures of White Mulberry (Morus alba)

Stilbene and benzofuran derivatives isolated from the root of white mulberry (Morus alba) have shown various biological activities, including anti-inflammatory, antioxidant, and antimicrobial properties. The objectives of this study were to develop hairy root cultures and assess the effect of multiple elicitors combinations including (I) methyl-β-cyclodextrin (CD), MgCl₂, methyl jasmonate (MeJA), and H₂O₂, (II) CD, MgCl₂, and MeJA and (III) CD, MgCl_2, and H₂O₂, on the production of these bioactive compounds. The highest yields of stilbenes and benzofurans were obtained upon co-treatment with 18 g/L CD, 3 mM H₂O₂ and 1 mM MgCl₂. The stilbenes oxyresveratrol, resveratrol, and 3'-prenylresveratrol accumulated up to 6.27, 0.61, and 5.00 mg/g DW root, respectively. Meanwhile, the aryl benzofurans moracin M and moracin C accumulated up to 7.82 and 1.82 mg/g DW root, respectively. These stilbenes and benzofurans accumulated in the culture medium of the elicited hairy root cultures. They were not detected in the root tissue. However, the oxyresveratrol diglucoside mulberroside A was only detected in the root tissue with yields up to 10.01 mg/g DW. The results demonstrated that co-treatment of white mulberry hairy root cultures with multiple elicitors can significantly enhance production and secretion of stilbenes and benzofurans in this controlled and sustainable axenic culture system.

Synthesis, Biosynthesis, and Biological Activity of Diels-Alder Adducts from Morus Genus: An Update

The plants of the Moraceae family are producers of a great variety of polyphenolic natural products. Among these, the Diels-Alder type adducts (DAAs) are endowed with a unique cyclohexene scaffold, since they are biosynthesized from [4+2] cycloaddition of different polyphenolic precursors such as chalcones and dehydroprenyl polyphenols. To date, more than 150 DAAs have been isolated and characterized from Moraceous and related plants. The main source of DAAs is the mulberry root bark, also known as "Sang-Bai-Pi" in Traditional Chinese Medicine, but they have also been isolated from root bark, stem barks, roots, stems or twigs, leaves, and callus cultures of Moraceous and other related plants. Since 1980, many biological activities of DAAs have been identified, including anti-HIV, antimicrobial, anti-inflammatory, and anticancer ones. For these reasons, natural DAAs have been intensively investigated, and a lot of efforts have been made to study their biosynthesis and to establish practical synthetic access. In this review, we summarized all the updated knowledge on biosynthesis, chemoenzymatic synthesis, racemic and enantioselective total synthesis, and biological activity of natural DAAs from Moraceous and related plants.

Mulberry Diels-Alder-type adducts: isolation, structure, bioactivity, and synthesis

Mulberry Diels-Alder-type adducts (MDAAs) are unique phenolic natural products biosynthetically derived from the intermolecular [4 + 2]-cycloaddition of dienophiles (mainly chalcones) and dehydroprenylphenol dienes, which are exclusively distributed in moraceous plants. A total of 166 MDAAs with diverse skeletons have been isolated and identified since 1980. Structurally, the classic MDAAs characterized by the chalcone-skeleton dienophiles can be divided into eight groups (Types A - H), while others with non-chalcone dienophiles or some variations of classic MDAAs are non-classic MDAAs (Type I). These compounds have attracted significant attention of natural products and synthetic chemists due to their complex architectures, remarkable biological activities, and synthetic challenges. The present review provides a comprehensive summary of the structural properties, bioactivities, and syntheses of MDAAs. Cited references were collected between 1980 and 2021 from the SciFinder, Web of Science, and China National Knowledge Internet (CNKI).

Chalcones, a Privileged Scaffold: Highly Versatile Molecules in [4+2] Cycloadditions

Chalcones are aromatic ketones found in nature as the central core of many biological compounds. They have a wide range of biological activity and are biogenetic precursors of other important molecules such as flavonoids. Their pharmacological relevance makes them a privileged scaffold, advantageous for seeking alternative therapies in medicinal chemistry. Due to their structural diversity and ease of synthesis, they are often employed as building blocks for chemical transformations. Chalcones have a carbonyl conjugated system with two electrophilic centers that are commonly used for nucleophilic additions, as described in numerous articles. They can also participate in Diels-Alder reactions, which are [4+2] cycloadditions between a diene and a dienophile. This microreview presents a chronological survey of studies on chalcones as dienes and dienophiles in Diels-Alder cycloadditions. Although these reactions occur in nature, isolation of chalcones from plants yields very small quantities. Contrarily, synthesis leads to large quantities at a low cost. Hence, novel methodologies have been developed for [4+2] cycloadditions, with chalcones serving as a 2π or 4π electron system.

Anti-Alzheimer chemical constituents of Morus macroura Miq.: chemical profiling, in silico and in vitro investigations

Herein, we investigated both fruits and leaves of Morus macroura Miq. as a potential source of bioactive compounds against Alzheimer's disease (AD). LC-HRMS-assisted chemical profiling of its extracts showed that they are a rich source of diverse phytochemicals. Among the 29 identified compounds in both the fruit and leaf extracts, moracin D, chrysin, resveratrol, and ferulic acid were predicted to pass the human blood-brain barrier (BBB), and hence, reach their therapeutic targets in the brain. Subsequently, these compounds were subjected to a comprehensive pharmacophore-based screening for their protein targets relevant to AD using two independent software programs (i.e. Swiss Target Prediction and PharmMapper). The results of this initial virtual screening were further refined by a number of docking and molecular dynamic simulation experiments to suggest a number of crucial AD-related proteins (e.g. acetylcholine esterase, β-secretase, and monoamine oxidase) as potential targets for these compounds. Finally, in vitro testing was performed to validate the in silico investigation's results, where chrysin, resveratrol, and ferulic acid were found to inhibit the predicted AD-related enzymes with IC₅₀ values comparable with those of the reference inhibitors. Additionally, they were able to inhibit the aggregation of amyloid-beta, one of the hallmarks in AD pathogenesis, and to exhibit considerable antioxidant capacity. Our results highlighted Morus macroura compounds as future anti-Alzheimer chemical leads.

A novel Diels-Alder adduct of mulberry leaves exerts anticancer effect through autophagy-mediated cell death

Guangsangon E (GSE) is a novel Diels-Alder adduct isolated from leaves of Morus alba L, a traditional Chinese medicine widely applied in respiratory diseases. It is reported that GSE has cytotoxic effect on cancer cells. In our research, we investigated its anticancer effect on respiratory cancer and revealed that GSE induces autophagy and apoptosis in lung and nasopharyngeal cancer cells. We first observed that GSE inhibits cell proliferation and induces apoptosis in A549 and CNE1 cells. Meanwhile, the upregulation of autophagosome marker LC3 and increased formation of GFP-LC3 puncta demonstrates the induction of autophagy in GSE-treated cells. Moreover, GSE increases the autophagy flux by enhancing lysosomal activity and the fusion of autophagosomes and lysosomes. Next, we investigated that endoplasmic reticulum (ER) stress is involved in autophagy induction by GSE. GSE activates the ER stress through reactive oxygen species (ROS) accumulation, which can be blocked by ROS scavenger NAC. Finally, inhibition of autophagy attenuates GSE-caused cell death, termed as "autophagy-mediated cell death." Taken together, we revealed the molecular mechanism of GSE against respiratory cancer, which demonstrates great potential of GSE in the treatment of representative cancer.

Total Synthesis of Mulberry Diels-Alder-Type Adducts Kuwanons G and H

Mulberry Diels-Alder-type adducts (MDAAs) are a group of rare natural polyphenols biosynthetically derived from [4 + 2]-cycloaddition of chalcones and dehydroprenylphenols. In this study, kuwanons G (1) and H (2), two bioactive MDAAs with unique dehydroprenylflavonoid dienes, were totally synthesized for the first time in a biomimetic manner. The key features of the convergent route include the use of the Baker-Venkataraman rearrangement, alkylation of β-diketone, intramolecular cyclization, and Suzuki-Miyaura coupling to achieve the subunit diene.

Chemoenzymatic Total Syntheses of Artonin I with an Intermolecular Diels-Alderase

Diels-Alder reaction is one of the most important transformations used in organic synthesis, with the ability to construct two new CC bonds and up to four chiral centers simultaneously. However, the biggest synthetic challenge in Diels-Alder reaction lies in controlling its regio-, diastereo-, and enantioselectivity. Using Stille cross-coupling and enzymatic Diels-Alder reaction as the key steps, the first chemoenzymatic total synthesis of artonin I is achieved in 30% overall yield over only seven steps. This enzymatic Diels-Alder reaction catalyzed by MaDA is featured with excellent endo- and enantioselectivity and high catalytic efficiency (k_cat /K_M = 362 ± 54 mm^-1  s^-1 ). These successful chemoenzymatic total syntheses of artonin I and dideoxyartonin I demonstrated the remarkable potential of the intermolecular Diels-Alderase MaDA in biocatalysis.

Inhibition of PTP1B by farnesylated 2-arylbenzofurans isolated from Morus alba root bark: unraveling the mechanism of inhibition based on in vitro and in silico studies

Among the 2-arylbenzofuran derivatives isolated from Morus alba, the farnesylated 2-arylbenzofuran is a rarer constituent. The derivative has been reported to exert anti-obesity effect; however, its inhibitory effect on protein tyrosine phosphatase 1B (PTP1B) has not been investigated. In the previous study, the presence of the farnesyl group in the structure of 2-arylbenzofurans was found to have positive influences on their pancreatic lipase inhibitory activity. In the present study, we have confirmed the authenticity of the notation based on the PTP1B inhibitory activity of farnesylated 2-arylbenzofurans. Specifically, two farnesylated 2-arylbenzofurans [morusalfurans B (2) and C (3)] showed strong inhibitory effects on PTP1B with IC₅₀ values of 8.92 and 7.26 µM, respectively, which was significantly higher than that of the positive controls [sodium orthovanadate (IC₅₀ = 15.10 µM) and ursolic acid (IC₅₀ = 11.34 µM)]. Besides, two 2-arylbenzofurans [morusalfurans A (1) and F (6)], one flavonoid [morusalnol B (9)], and one geranylated stilbene [morusibene A (11)] exhibited PTP1B inhibition with IC₅₀ values ranging from 11.02 to 26.56 µM. Kinetic studies revealed compounds 2, 3, 6, and 11 as mixed type PTP1B inhibitors, while 1 and 9 are known as noncompetitive. Molecular docking simulations demonstrated that these active compounds can bind with the respective catalytic or/and allosteric sites of PTP1B with negative binding energies and the results are in accordance with that of the kinetic studies. To the best of our knowledge, this is the first time, the PTP1B inhibitory activity of eleven compounds (1–11), as well as the mechanism of action underlying the effects on PTP1B enzyme of the active compounds, were investigated. In vitro and in silico results suggest that the farnesylated 2-arylbenzofurans from M. alba may potentially be utilized as an effective treatment therapy for type 2 diabetes mellitus and its associated complications.

Comparative Study of the Antioxidant and Anti-Inflammatory Effects of Leaf Extracts from Four Different Morus alba Genotypes in High Fat Diet-Induced Obesity in Mice

Increased levels of reactive oxygen species (ROS) and a low-grade chronic inflammation in multiple organs have been demonstrated in obesity. Morus alba leaves extracts (MAEs) have been used in traditional medicine as anti-inflammatory agents. In this work, the bioactive compounds of different genotypes of M. alba L. (Filipina, Valenciana Temprana, Kokuso, and Italia) were analyzed not only by reverse phase high performance liquid chromatography–electrospray ionization-time of flight-mass spectrometry (RP-HPLC-ESI-TOF-MS) and hydrophilic interaction chromatography–electrospray ionization-time of flight-mass spectrometry (HILIC-ESI-TOF-MS), but also screened for in vitro and in vivo antioxidant activity by means of DPPH• radical scavenging assay and Caenorhabditis elegans model. These MAEs were administered daily in a model of diet-induced obesity in mice. Filipina and Italia genotypes significantly reduced weight gain, the glycemic levels in high fat diet, as well as, levels of LDL-cholesterol and triglycerides. Filipina and Italia MAEs also reduced the expression of proinflammatory mediators such as Tnf-α, Il-1β, Il-6 and increased the levels of adiponectin and AMPK, which exert anti-inflammatory effects. Moreover, Italia genotype ameliorated the intestinal barrier function. In conclusion, Filipina and Italia methanolic extracts show the highest antioxidant and anti-inflammatory effect, due to the presence of compounds such as protocatechuic acid or quercetin-3-glucoside, and they could be developed as a complementary treatment for obesity and metabolic disorders.

The structure-activity relationship review of the main bioactive constituents of Morus genus plants

Abstract

Morus genus plants are mainly distributed in the temperate to tropical areas over the world and include 17 species and two subspecies. Due to their excellent pharmacological activity, security in food additives and high value in the national economy, Morus genus plants have drawn more and more attention in recent years. In the light of the references published over the last few decades, flavonoids, benzofurans, stilbenes, and Diels–Alder adducts have been reported to be the main bioactive constituents of Morus genus plants. This review summarizes the compounds with excellent bioactivities isolated from Morus genus plants as well as their structure–activity relationships (SARs), which might be useful for the further research and development of Morus genus plants.

Graphic abstract

The aromatic heterocycles with excellent bioactivities isolated from Morus genus plants as well as their structure–activity relationships (SARs) were summarized.

Potential cytotoxic Diels-Alder type adducts from liquid medium of Morus Alba var. shalun root cultures

A new Diels-Alder type adduct named morushalunin (1), together with three similar compounds, guangsangon E (2), chalcomoracin (3), and kuwanon J (4) were isolated from the EtOAc extract of liquid medium of Morus alba var. shalun root cultures. The structures of the isolated compounds were determined based on spectroscopic data, including 1D, 2D NMR, and MS data. Cytotoxic properties of compounds 1-4 were evaluated against murine leukemia P-388 cells. Morushalunin (1), guangsangon E (2), and chalcomoracin (3) were found to have significant cytotoxicity with IC₅₀ values 0.7, 2.5, and 1.7 μg/mL, respectively, while kuwanon J (4) showed weak cytotoxicity (IC₅₀ = 5.9 μg/mL).

Morus alba, a Medicinal Plant for Appetite Suppression and Weight Loss

The prevalence of obesity is expanding rapidly worldwide, making the disease a global burden with limited treatment options. The current obesity drug development trends suggest the possibility of reducing weight and reverse metabolic disturbances of obesity by controlling appetite. In this study, we screened more than 8000 plants from our plant library for the cannabinoid (CB₁) receptor antagonists and identified Morus alba as a lead medicinal plant. Kuwanon G and Albanin G were isolated and identified from root-barks of Morus alba with 92% and 96% CB₁ receptor ligand binding inhibitory activity, respectively. The bioflavonoid standardized extract was tested in the acute food intake study in rats at oral doses of 250 and 500 mg/kg for its appetite suppression activity. Diet-induced obesity in the C57BL/6J mice was used to evaluate the long-term food intake reduction activity and effect on the weight loss administered orally at 250 and 500 mg/kg for 7 weeks. Statistically significant and dose-dependent reduction in food intake was observed in both acute and long-term studies for the extract. Food intake reductions of 58.6% and 44.8% at 250 mg/kg and 50.1% and 44.3% at 500 mg/kg were observed at 1 and 2 h postfood provision, respectively. A 20% reduction in daily calorie intake was observed in the long-term study. Obese mice treated with the high dose of Morus root-bark extract showed 10.4 g (22.5%) and 7.1 g (16.5%) loss in body weight compared with the vehicle-treated obese animals (at week 7) and baseline, respectively. Statistically significant reductions in biochemical markers and visceral fat deposit were also observed. These results demonstrated that Morus alba extracts enriched in Kuwanon G, and Albanin G could be used alone to control appetite, manage body weight, and improve metabolic syndromes.

Pharmacological Properties of Morus nigra L. (Black Mulberry) as A Promising Nutraceutical Resource

Mulberry plants belonging to the Moraceae family have been grown for the purpose of being the nutrient source for silk worm and raw materials for the preparation of jams, marmalades, vinegars, juices, wines, and cosmetics. Morus nigra L. (black mulberry) is native to Southwestern Asia, and it has been used as a traditional herbal medicine for animals and humans. In this article, recent research progress on various biological and pharmacological properties of extracts, fractions, and isolated active constituents from different parts of M. nigra are reviewed. M. nigra exhibited a wide-spectrum of biological and pharmacological therapeutic effects including antinociceptive, anti-inflammatory, antimicrobial, anti-melanogenic, antidiabetic, anti-obesity, anti-hyperlipidemic, and anticancer activities. M. nigra also showed protective effects against various human organs and systems, mainly based on its antioxidant capacity. These findings strongly suggest that M. nigra can be used as a promising nutraceutical resource to control and prevent various chronic diseases.

Mulberry Diels-Alder-type adducts from Morus alba as multi-targeted agents for Alzheimer's disease

Mulberry Diels-Alder-type adducts (MDAAs) are a group of structurally unique natural products biosynthetically derived from the intermolecular [4 + 2] cycloaddition of a dehydroprenylphenol and a chalcone. In the current study, ten MDAAs, including an undescribed one, inethermulberrofuran C, were isolated from the root bark of Morus alba. The anti-Alzheimer's disease (anti-AD) properties of these isolates were systematically screened for a series of potential targets (Aβ self-aggregation, tau aggregation, and ChEs) as well as the anti-neuroinflammatory and neuroprotective activities. Four compounds, mulberrofuran C, mulberrofuran K, mulberrofuran G, and isomulberrofuran G, turned out to be potent multi-targeted agents for AD. Among them, mulberrofuran K with a good blood-brain barrier (BBB) permeability (8.7 ± 0.3 × 10^-6 cm/s) was selected as a promising candidate for further mechanism study in glutamate-induced HT22 cell model, which showed its neuroprotective ability on up-regulation of the glutathione (GSH) level and suppression of the reactive oxygen species (ROS) production.

Molecular Characterization of a Geranyl Diphosphate-Specific Prenyltransferase Catalyzing Stilbenoid Prenylation from Morus alba

Pharmaceutically active compounds from medical plants are attractive as a major source for new drug development. Prenylated stilbenoids with increased lipophilicity are valuable secondary metabolites which possess a wide range of biological activities. So far, many prenylated stilbenoids have been isolated from Morus alba but the enzyme responsible for the crucial prenyl modification remains unknown. In the present study, a stilbenoid-specific prenyltransferase (PT), termed Morus alba oxyresveratrol geranyltransferase (MaOGT), was identified and functionally characterized in vitro. MaOGT recognized oxyresveratrol and geranyl diphosphate (GPP) as natural substrates, and catalyzed oxyresveratrol prenylation. Our results indicated that MaOGT shared common features with other aromatic PTs, e.g. multiple transmembrane regions, conserved functional domains and targeting to plant plastids. This distinct PT represents the first stilbenoid-specific PT accepting GPP as a natural prenyl donor, and could help identify additional functionally varied PTs in moraceous plants. Furthermore, MaOGT might be applied for high-efficiency and large-scale prenylation of oxyresveratrol to produce bioactive compounds for potential therapeutic applications.

Chalcone derivatives from the root bark of Morus alba L. act as inhibitors of PTP1B and α-glucosidase

As part of our continuing research to obtain pharmacologically active compounds from Morus alba L. (Moraceae), four Diels-Alder type adducts (DAs) [morusalbins A-D], one isoprenylated flavonoid [albanin T], together with twenty-one known phenolic compounds were isolated from its root bark. The chemical structures were established using NMR, MS, and ECD spectra. The DAs including morusalbins A-D, albasin B, macrourin G, yunanensin A, mulberrofuran G and K, and albanol B exhibited strong inhibitory activities against both protein tyrosine phosphatase 1B (PTP1B) (IC₅₀, 1.90-9.67 μM) and α-glucosidase (IC₅₀, 2.29-5.91 μM). In the kinetic study, morusalbin D, albasin B, and macrourin G showed noncompetitive PTP1B inhibition, with K_i values of 0.33, 1.00, and 1.09 μM, respectively. In contrast, these DAs together with yunanensin A produced competitive inhibition of α-glucosidase, with K_i values of 0.64, 0.42, 2.42, and 1.19 μM, respectively. Furthermore, molecular docking studies revealed that these active DAs have high affinity and tight binding capacity towards the active site of PTP1B and α-glucosidase.

Protein Tyrosine Phosphatase 1B Inhibition and Glucose Uptake Potentials of Mulberrofuran G, Albanol B, and Kuwanon G from Root Bark of Morus alba L. in Insulin-Resistant HepG2 Cells: An In Vitro and In Silico Study

Type II diabetes mellitus (T2DM) is the most common form of diabetes and has become a major health problem across the world. The root bark of Morus alba L. is widely used in Traditional Chinese Medicine for treatment and management of diabetes. The aim of the present study was to evaluate the enzyme inhibitory potentials of three principle components, mulberrofuran G (1), albanol B (2), and kuwanon G (3) in M. alba root bark against diabetes, establish their enzyme kinetics, carry out a molecular docking simulation, and demonstrate the glucose uptake activity in insulin-resistant HepG2 cells. Compounds 1–3 showed potent mixed-type enzyme inhibition against protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase. In particular, molecular docking simulations of 1–3 demonstrated negative binding energies in both enzymes. Moreover, 1–3 were non-toxic up to 5 µM concentration in HepG2 cells and enhanced glucose uptake significantly and decreased PTP1B expression in a dose-dependent manner in insulin-resistant HepG2 cells. Our overall results depict 1–3 from M. alba root bark as dual inhibitors of PTP1B and α-glucosidase enzymes, as well as insulin sensitizers. These active constituents in M. alba may potentially be utilized as an effective treatment for T2DM.

A Chemical Investigation of the Leaves of Morus alba L

The leaves of Morus alba L. are an important herbal medicine in Asia. The systematic isolation of the metabolites of the leaves of Morus alba L. was achieved using a combination of liquid chromatography techniques. The structures were elucidated by spectroscopic data analysis and the absolute configuration was determined based on electronic circular dichroism (ECD) spectroscopic data and hydrolysis experiments. Their biological activity was evaluated using different biological assays, such as the assessment of their capacity to inhibit the aldose reductase enzyme; the determination of their cytotoxic activity and the evaluation of their neuroprotective effects against the deprivation of serum or against the presence of nicouline. Chemical investigation of the leaves of Morus alba L. resulted in four new structures 1⁻4 and a known molecule 5. Compounds 2 and 5 inhibited aldose reductase with IC₅₀ values of 4.33 μM and 6.0 μM compared with the potent AR inhibitor epalrestat (IC₅₀ 1.88 × 10⁻³ μM). Pretreatment with compound 3 decreased PC12 cell apoptosis subsequent serum deprivation condition and pretreatment with compound 5 decreased nicouline-induced PC12 cell apoptosis as compared with control cells (p < 0.001).

Repeated dose 28-day oral toxicity study of a botanical composition composed of Morus alba and Acacia catechu in rats

Patients with osteoarthritis experience debilitating pain and loss of joint function that requires chronic treatment. While nonsteroidal anti-inflammatory drugs (NSAIDs) have been effective for temporary symptomatic relief, their long term usage has been limited by their associated side-effects. UP1306, a standardized novel composition from the extracts of root barks of Morus alba and the heartwoods of Acacia catechu, has been used in over the counter joint care dietary supplements as a safer alternative. These two medicinal plants have long track records of safe human consumption. Here we evaluated the potential adverse effects of orally administered UP1306 in Sprague Dawley rats following a 28-day repeated oral dose toxicity study. UP1306 at doses of 500, 1000 and 2000 mg/kg/day were administered orally to rats for 4 weeks. A 2-week recovery group from the high dose (2000 mg/kg) and vehicle treated groups were included. No morbidity or mortality was observed for the duration of the study. No significant differences between groups in body weights, food consumption, hematology, clinical chemistry, organ weights, gross pathology and histopathology were documented. Minor aberrations from the normal observed for the main groups were considered reversible as they were not evident in the recovery period. In conclusion, the no-observed-adverse-effect-level (NOAEL) of UP1306 was considered to be the highest dose tested, 2000 mg/kg/day, both for male and female rats.

A Tri-O-Bridged Diels-Alder Adduct from Cortex Mori Radicis

Sanggenon X, an unusual tri-O-bridged Diels-Alder adduct, was isolated from Cortex Mori Radicis. Its structure was established by spectroscopic analysis, including NMR and HR-MS (High Resolution Mass Spectrometry). Sanggenon X contained three O-bridged rings, where the oxygenated bridgeheads were all quaternary carbons. Chemical methylation was carried out to deduce the linkages of the three O-bridges. The absolute configuration was determined by calculating the ECD (Electronic Circular Dichroism) using the TDDFT (Time-Dependent Density Functional Theory) method. Sanggenon X showed significant antioxidant activity against Fe²⁺-Cys-induced lipid peroxidation in rat liver microsomes, and was as effective as the positive control, curcumin.

UP601, a standardized botanical composition composed of Morus alba, Yerba mate and Magnolia officinalis for weight loss

Background

The prevalence of obesity is surging in an alarming rate all over the world. Pharmaceutical drugs are considered potential adjunctive therapy to lifestyle modification. However, for most, besides being too expensive, their long term usages are hindered by their severe adverse effects. Here we describe the effect of UP601, a standardized blend of extracts from Morus alba, Yerba mate and Magnolia officinalis, in modulating a number of obesity-related phenotypic and biochemical markers in a high-fat high-fructose (HFF)-induced C57BL/6J mouse model of obesity.

Method

Adipogenesis activity of the composition was assessed in 3T3-L1 cells in vitro. Effects of UP601 on body weight and metabolic markers were evaluated. It was administered at oral doses of 300 mg/kg, 450 mg/kg and 600 mg/kg for 7 weeks. Orlistat (40 mg/kg/day) was used as a positive control. Body compositions of mice were assessed using dual energy X-ray absorptiometry (DEXA). Serum biomarkers were measured for liver function and lipid profiling. Relative organ weights were determined. Histopathological analysis was performed for non-alcoholic steatohepatitis (NASH) scoring.

Results

UP601 at 250 μg/ml resulted in 1.8-fold increase in lipolysis. Statistically significant changes in body weight (decreased by 9.1, 19.6 and 25.6% compared to the HFF group at week-7) were observed for mice treated with UP601 at 300, 450 and 600 mg/kg, respectively. Reductions of 9.1, 16.9, and 18.6% in total cholesterol; 45.0, 55.0, 63.6% in triglyceride; 34.8, 37.1 and 41.6% in LDL; 3.2, 21.6 (P = 0.03) and 33.7% (P = 0.005) in serum glucose were observed for UP601 at 300, 450 and 600 mg/kg, respectively. Body fat distribution was found reduced by 31.6 and 17.2% for the 450 mg/kg UP601 and orlistat, respectively, from the DEXA scan analysis. Up to an 89.1% reduction in mesenteric fat deposit was observed for UP601 in relative organ weight. Statistically significant improvements in NASH scores were observed for mice treated with UP601.

Conclusion

UP601, a standardized botanical composition from Morus alba, Yerba mate and Magnolia officinalis could potentially be used for achieving healthy weight loss and maintenance.

Bioactive Benzofuran Derivatives from Cortex Mori Radicis, and Their Neuroprotective and Analgesic Activities Mediated by mGluR₁

Four new benzofuran-type stilbene glycosides and 14 known compounds including 8 benzofuran-type stilbenes and 6 flavonoids were isolated from the traditional Chinese medicine, Cortex Mori Radicis. The new compounds were identified as (9R)-moracin P 3′-O-α-l-arabinopyranoside (1), (9R)-moracin P 9-O-β-d-glucopyranoside (2), (9R)-moracin P 3′-O-β-d-glucopyranoside (3), and (9R)-moracin O 10-O-β-d-glucopyranoside (4) based on the spectroscopic interpretation and chemical analysis. Three benzofuran-type stilbenes, moracin O (5), R (7), and P (8) showed significant neuroprotective activity against glutamate-induced cell death in SK-N-SH cells. In addition, moracin O (5) and P (8) also demonstrated a remarkable inhibition of the acetic acid-induced pain. The molecular docking with metabotropic glutamate receptor 1 (mGluR₁) results indicated that these neuroprotective benzofuran-type stilbenes might be the active analgesic components of the genus Morus, and acted by mediating the mGluR₁ pathway.

Root bark of Morus alba ameliorates the depressive-like behaviors in diabetic rats

Diabetes-induced depression is one of the severe chronic complications of diabetes mellitus. Up to now, there are only a few effective medicines to prevent or manage the co-morbidity of diabetes and depression. The present study was to investigate the effect of root bark of Morus alba (RBM) on depressive-like behaviors in the diabetic rats established by a high fat diet and a low dose of streptozotocin. Depressive-like behaviors were measured by the open field test, locomotor activity test and forced swimming test. Plasma glucose and lipid parameters were also measured. Expression of Brain-derived neurotrophic factor (BDNF) and phosphorylation of extracellular signal-regulated kinase (ERK) and Akt in the prefrontal cortex (PFC) were assessed. The results showed that a 4-week administration of RBM (10g/kg, ig) significantly reversed the depressive-like behaviors. BDNF expression and phosphorylation of ERK and Akt were increased in the PFC following RBM treatment in the diabetic rats. The data demonstrated that RBM could improve the depressive-like behaviors induced by diabetes, suggesting a therapeutic potential of RBM for the diabetes-associated depression.

The Immunomodulatory Activity of Mori folium, the Leaf of Morus alba L., in RAW 264.7 Macrophages In Vitro

Background

Immunoregulatory elements have emerged as useful immunotherapeutic agents against cancer. In traditional medicine, Mori folium, the leaf of Morus alba L. (Moraceae), has been used for various medicinal purposes; however, the immunomodulatory effects have not been fully identified. We evaluated the immunoenhancing potential of water extract of Mori folium (WEMF) in murine RAW264.7 macrophages.

Methods

RAW264.7 cells were treated with WEMF for 24 hours and cell viability was detected by an MTT method. Nitric oxide (NO) levels in the culture supernatants were assayed using Griess reagent. The productions of prostaglandin E₂ (PGE₂) and immune-related cytokines was measured using ELISA detection kits. The mRNA and protein expression levels of Inducible NO synthase, COX-2, and cytokines were assayed by reverse transcription-PCR and Western blotting, respectively. The effect of WEMF on phagocytic activity was measured using a Phagocytosis Assay Kit.

Results

WEMF significantly stimulated the production of NO and PGE₂ as immune response parameters at noncytotoxic concentrations, which was associated with the increased expression of inducible NO synthase and COX-2. The release and expression of cytokines, such as TNF-α, interleukin (IL)-1β, IL-6, and IL-10, were also significantly increased in response to treatment with WEMF. Moreover, WEMF promoted the macrophagic differentiation of RAW264.7 cells and the resulting phagocytosis activity.

Conclusions

WEMF has the potential to modulate the immune function by regulating immunological parameters. Further studies are needed to identify the active compounds and to support the use of WEMF as an immune stimulant.

Nonclinical Safety Assessment of Morus alba L. Fruits: Study of 90-D Toxicity in Sprague Dawley Rats and Genotoxicity in Salmonella

Morus alba L. is a traditional herb with a long history of consumption, both as an edible fruit and as medicine. However, its safety evaluation has not yet been established. The objective of this study was to evaluate subchronic oral toxicity and genotoxicity of M. alba L. fruits (MFE). The subchronic toxicity after daily oral administration of MFE at 0, 40, 200, and 1000 mg/kg for 90 d was examined in Sprague Dawley (SD) rats. MFE administration did not lead to death, adverse effects, change in food and water consumption, and body weight gain. Significant toxic effects were not found within the parameters of organ weight, biochemical values, and hematological and urine analysis between the control and the MFE group. The genotoxicity of MFE was assayed by Ames test in Salmonella typhimurium strains TA98, TA102, and TA1535. No genotoxicity was found in all the tested strains. Thus in this study, a no-observed-adverse-effect level for MFE in 90 d repeated oral toxicity study in rats was determined to be greater than 1000 mg/kg regardless of gender. The results also suggested that MFE does not have a genotoxicity potential.