Diels-Alder Type Adducts Research Articles

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.

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.

HPLC-HRESI-MSn Characterization of Polyphenolic Compounds in the Stem Bark of Chlorophora regia A. Chev (Moraceae)

Isolation and identification of secondary metabolites from medicinal plants could be tedious and time consuming. Therefore, any technique that could be used to confirm the identity of medicinal plant constituents without isolating them will save time and resources. Chlorophora similar to many genera in the Moraceae family have been demonstrated to be rich sources of polyphenolic compounds with important biological activities. The current study was designed to employ HRESI-MSn analyses to qualitatively examine isolated polyphenolic compounds from the stem bark of Chlorophora regia. Based on the HRESI-MSn data obtained, the fragmentation patterns of the compounds under study will be proposed and could be used in their identification in a matrix. Five polyphenolic compounds were successfully isolated and purified using various chromatographic techniques including column chromatography, thin-layer chromatography (TLC) and preparative HPLC. The structures of the isolated compounds were elucidated by in-depth analyses of their 1D and 2D NMR and mass spectroscopic data. HRESI-MS/MS was further used to characterize the isolated compounds. Five polyphenolic compounds including three Diels-Alder type adducts: sanggenon C, kuwanol E and chalcomoracin; two stilbene derivatives: chlorophorin and isochlorophorin were isolated from the stem bark. The tandem MS fragmentation patterns of the compounds in positive mode, were successfully proposed. The fragments obtained and proposed fragmentation patterns of the isolated compounds could be employed qualitatively in the identification of the studied polyphenolic compounds in a matrix.

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.

Inhibition Mechanism of Components Isolated from Morus alba Branches on Diabetes and Diabetic Complications via Experimental and Molecular Docking Analyses.

Previously, we reported the anti-diabetic effect of Morus alba root bark and the compounds therein. In our continuous study of other parts of this plant, the ability of the branch of Morus alba to inhibit α-glucosidase, protein tyrosine phosphatase 1B (PTP1B), and advanced glycation end products (AGEs) formation was evaluated. Moreover, there are no previous studies that have performed enzyme kinetics and molecular docking analyses, along with assessments of peroxynitrite (ONOO−) inhibitory activities. Since the Morus alba branch exhibited favorable inhibitory effects, repeated column chromatography was performed to obtain eight compounds, including four flavonoids (1, 3, 6, 8), one arylbenzofuran (2), one stilbene (5), one Diels–Alder-type adduct (7), and one sterol (4). Among them, compounds 1–3 and 5–7 were mixed-type inhibitors of α-glucosidase, sharing the same catalytic residues with acarbose and the same allosteric sites with (Z)-3-bytylidenephthalide. On the other hand, kuwanon C (1) and oxyresveratrol (5) interacted with residues of the allosteric site (α3 and α6 helices) of PTP1B, indicating their use as non-competitive inhibitors. Interestingly, kuwanon G (7) directly bound the catalytic site, or interrupted the binding between the substrate and the active site, as a mixed-type inhibitor. Moreover, most of the compounds exhibited greater activity against AGE formation and ONOO− than positive controls. The IC50 values required to inhibit ONOO− using compounds 1, 3, 5, 6, and 7 were reported for the first time, and range from 1.08 to 12.92 μM. Based on the structure–activity relationship, the presence of hydroxyl, resorcinol, and prenyl moieties was important in the prevention of diabetes’ pathological mechanisms, and these findings have been further supported by molecular docking analysis. These computational and experimental results will be useful in the development of therapeutic candidates to prevent/treat diabetes and its complications.

Vasorelaxant Effect of Boesenbergia rotunda and Its Active Ingredients on an Isolated Coronary Artery.

Cardiovascular diseases are a major cause of death in developed countries. The regulation of vascular tone is a major approach to prevent and ameliorate vascular diseases. As part of our ongoing screening for cardioprotective natural compounds, we investigated the vasorelaxant effect of rhizomes from Boesenbergia rotunda (L.) Mansf. [Boesenbergia pandurata (Roxb.) Schltr.] used as a spice and herbal medicine in Asian countries. The methanol extract of B. rotunda rhizomes (BRE) exhibited significant vasorelaxation effects ex vivo at EC50 values of 13.4 ± 6.1 μg/mL and 40.9 ± 7.9 μg/mL, respectively, with and without endothelium in the porcine coronary artery ring. The intrinsic mechanism was evaluated by treating with specific inhibitors or activators that typically affect vascular reactivity. The results suggested that BRE induced relaxation in the coronary artery rings via an endothelium-dependent pathway involving NO-cGMP, and also via an endothelium-independent pathway involving the blockade of Ca2+ channels. Vasorelaxant principles in BRE were identified by subsequent chromatographic methods, which revealed that flavonoids regulate vasorelaxant activity in BRE. One of the flavonoids was a Diels-Alder type adduct, 4-hydroxypanduratin A, which showed the most potent vasorelaxant effect on porcine coronary artery with an EC50 of 17.8 ± 2.5 μM. Our results suggest that rhizomes of B. rotunda might be of interest as herbal medicine against cardiovascular diseases.

Morusalisins A-F, six new Diels-Alder type adducts, as potential PTP1B inhibitors from cell cultures of Morus alba

Six new Diels-Alder type adducts, morusalisins A-F (1–6), were isolated from Morus alba cell cultures. The structures of 1–6 were determined by extensive spectroscopic data analysis, including HRESIMS, NMR, and ECD experiments. Furthermore, compounds 1–6 exhibited potent protein tyrosine phosphatase 1B (PTP1B) inhibitory activity with IC50 values ranging from 1.14 to 2.24 μM, making them promising as bioactive compounds for anti-diabetic drug discovery.

Novel Diels-Alder Type Adducts from Morus alba Root Bark Targeting Human Monoamine Oxidase and Dopaminergic Receptors for the Management of Neurodegenerative Diseases.

In this study, we delineate the human monoamine oxidase (hMAO) inhibitory potential of natural Diels–Alder type adducts, mulberrofuran G (1), kuwanon G (2), and albanol B (3), from Morus alba root bark to characterize their role in Parkinson’s disease (PD) and depression, focusing on their ability to modulate dopaminergic receptors (D1R, D2LR, D3R, and D4R). In hMAO-A inhibition, 1–3 showed mild effects (50% inhibitory concentration (IC50): 54‒114 μM). However, 1 displayed moderate inhibition of the hMAO-B isozyme (IC50: 18.14 ± 1.06 μM) followed by mild inhibition by 2 (IC50: 57.71 ± 2.12 μM) and 3 (IC50: 90.59 ± 1.72 μM). Our kinetic study characterized the inhibition mode, and the in silico docking predicted that the moderate inhibitor 1 would have the lowest binding energy. Similarly, cell-based G protein-coupled receptors (GPCR) functional assays in vector-transfected cells expressing dopamine (DA) receptors characterized 1–3 as D1R/D2LR antagonists and D3R/D4R agonists. The half-maximum effective concentration (EC50) of 1–3 on DA D3R/D4R was 15.13/17.19, 20.18/21.05, and 12.63/‒ µM, respectively. Similarly, 1–3 inhibited 50% of the DA response on D1R/D2LR by 6.13/2.41, 16.48/31.22, and 7.16/18.42 µM, respectively. A computational study revealed low binding energy for the test ligands. Interactions with residues Asp110, Val111, Tyr365, and Phe345 at the D3R receptor and Asp115 and His414 at the D4R receptor explain the high agonist effect. Likewise, Asp187 at D1R and Asp114 at D2LR play a crucial role in the antagonist effects of the ligand binding. Our overall results depict 1–3 from M. alba root bark as good inhibitors of hMAO and potent modulators of DA function as D1R/D2LR antagonists and D3R/D4R agonists. These active constituents in M. alba deserve in-depth study for their potential to manage neurodegenerative disorders (NDs), particularly PD and psychosis.

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 leaf extract: Metabolite profiling and interactions with antibiotics against Staphylococcus spp. including MRSA

HPLC-DAD-ESI-Q-TOF-MS/MS metabolite profiling of Morus alba leaf extract led to the annotation of 25 constituents (two stilbene derivatives, 11 prenylflavonoids, five 2-arylbenzofurans, seven Diels–Alder type adducts). The extract was found to contain 57.83 mg/g flavonoids, 15.42 mg/g kuwanon G and 10.47 mg/g morusin. Despite its moderate antibacterial activity with minimum inhibitory concentration (MIC) values of 250 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 33591 and ATCC 43300, methicillin-susceptible S. aureus (MSSA) ATCC 6538 and S. epidermidis ATCC 12228, Morus alba leaf extract reversed oxacillin-resistance of MRSA ATCC 43300. In addition, the extract showed synergy with gentamicin against MRSA ATCC 33591 and ATCC 43300 and S. epidermidis ATCC 12228, oxacillin against MRSA ATCC 33591 and tetracycline against S. epidermidis ATCC 12228. In these synergistic combinations, MIC values of antibiotics were significantly decreased (4–32-fold). These findings might be valuable for the development of novel treatment strategies in infections caused by MRSA and S. epidermidis.

Sanggenon O induced apoptosis of A549 cells is counterbalanced by protective autophagy

Sanggenon O (SO) is a Diels-Alder type adduct extracted fromMorus alba, which has been used for its anti-inflammatory action in the Oriental medicine. However, whether it has regulatory effect on human cancer cell proliferation and what the underlying mechanism remains unknown. Here, we found that SO could significantly inhibit the growth and proliferation of A549 cells and induce its pro-apoptotic action through a caspase-dependent pathway. It could also impair the mitochondria which can be reflected by mitochondrial membrane permeabilization. Besides, SQSTM1 up-regulation and autophagic flux measurement demonstrated that exposure to SO led to autophagosome accumulation, which plays a protective role in SO-treated cells. In addition, knocking down of LC3B increased SO triggered apoptotic cell rates. These results indicated that SO has great potential as a promising candidate combined with autophagy inhibitor for the treatment of NSCLC. In conclusion, our results identified a novel mechanism by which SO exerts potent anticancer activity.

Diels-Alder Type Adducts from Hairy Root Cultures of Morus macroura

Diels-Alder Type Adducts from Hairy Root Cultures of <i>Morus macroura</i>

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 Ki 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 Ki 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.

Diels–Alder type adducts with potent alpha-glucosidase inhibitory activity from Morus macroura

Two new Diels–Alder type adducts, macrourins I and J (1–2), along with seven known analogues (3–9) were isolated from the stems of Morus macroura Miq. The structures of the two new compounds were elucidated by extensive analysis of spectroscopic data. Compounds 1–9 all showed highly potent in vitro α-glucosidase inhibitory activities, and the IC50 values of compounds 1 and 2 were 1.70 and 1.58 μM, respectively, approximately 800 times stronger than the positive control, acarbose.

Characteristic Components, Biological Activities and Future Prospective of Fructus Mori: a Review

China has a long history in planting mulberry with the most varieties and the largest production in the world. This article provides a brief overview of an important edible fruit and traditional medicine in China—Fructus Mori (FM, mulberry fruit or Morus alba L. fruit), including the main chemical constituents, major bioactivities and the future prospective. Phytochemical studies have revealed that Fructus Mori contains a great diversity of nutritive compounds such as organic acids, amino acids, vitamins, minerals, and bioactive components, including polysaccharides, polyphenolics, anthocyanins, flavonoids, alkaloids, stilbenes, and diels-alder type adducts. Besides, the extracts and active components of FM were reported to have numerous biological activities, including antioxidant, antihyperglycemic, antitumor, hepatoprotective, and neuroprotective activities in in vitro and in vivo studies. This review provides recent findings systematically regarding the structural characteristics and biological activities of FM, which may be useful for stimulating deep research of therapeutic potentials and for predicting their uses as important and safe functional foods to benefit human health.

Artemisians A-D, Diseco-guaianolide Involved Heterodimeric [4 + 2] Adducts from Artemisia argyi.

Artemisians A-D (1-4), the first examples of [4 + 2] Diels-Alder type adducts presumably biosynthesized from a rare 1, 10-4, 5-diseco-guaianolide and a guaianolide diene, along with their possible precursor 5, were isolated from the traditional Chinese medicine Artemisia argyi. The structures of 1-4 were elucidated by extensive spectroscopic analyses and calculated electronic circular dichroism. Compound 2, with an IC50 value of 3.21 μM, exhibited significant antiproliferative activity via apoptosis induction and G2/M arrest in MDA-MB-468 cells.

New cytotoxic diels-alder type adducts from root cultures of Morus alba var. shalun

New cytotoxic diels-alder type adducts from root cultures of Morus alba var. shalun

Preparation of 3-(9-Anthryl)acrylates and 9-Aroylethenylanthracenes as Pi-Extended Anthracenes and Their Diels–Alder Type Adducts with Electron-Poor Dienophiles

ABSTRACT(E)-3-(9-Anthryl)acrylates and (E)-9-aroylethenylanthracenes have been prepared by solventless Wittig olefination with conjugated phosphoranes. The (E)-3-(9-anthryl)acrylates were brominated to give (E)-3[10-{9-bromoanthryl}]acrylates, which could be subjected to Suzuki reactions with arylboronic acids to produce (E)-3-[10-{9-arylanthryl}]acrylates as pi-extended systems. The compounds thus prepared were subjected to Diels–Alder reactions, partly under solventless conditions.

Review of bioactive compounds from root barks of Morus plants (Sang-Bai-Pi) and their pharmacological effects

AbstractMorus, a plant genus from the family of Moraceae, most plants of which are used as traditional medicines in Asian counties. The root barks of Morus plants are normally called as Sang-Bai-Pi (SBP) in Chinese and used for the treatment of inflammatory and respiratory diseases. Decades of research on phytochemistry of SBP have led to the identification of various compounds, such as Diels–Alder-type adducts, flavonoids, benzofurans, stilbenes, polyhydroxylated alkaloids, etc. These compounds have showed a wide range of bioactive features including anti-inflammatory, anti-oxidative, anti-microbic, etc. This review focus on the bioactive compounds and their pharmacological effects of SBP which will help us fully understand the effective substances of SBP, and pave our way to further explore medicinal uses of SBP and comprehensive utilization of Morus species.

Diels-Alder type adducts from the fruits ofMorus albaL.

The fruits of Morus alba L. were extracted with 80 % aqueous MeOH, and the concentrated extract was partitioned into EtOAc, n-butyl alcohol, and water fractions. The repeated silica gel () and octadecyl silica gel column chromatographies for the EtOAc and n-butyl alcohol fractions led to isolation of two phenolic compounds. The chemical structures of the compounds were determined as Diels-Alder type adducts, mulberrofuran E (1) and chalcomoracin (2) based on spectroscopic data analyses including nuclear magnetic resonance, mass spectrometry, and infrared spectrometry. Compounds 1 and 2 were isolated for the first time from the fruits of M. alba L. in this study.