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

Black mulberry (Morus nigra L.) prevents deleterious effects of excess glucose in obese C. elegans decreasing lipofuscin accumulation and ROS production

Black mulberries have been traditionally used as antidiabetic agents and are a source of nutrients and phenolic compounds, particularly anthocyanins. The objective of this work is to determine if Morus nigra berries could prevent metabolic and obesity-related disorders using in vitro systems and in vivo alternative models such as C. elegans. An aqueous solvent-free extract from Morus nigra fruits rich in phenolic compounds like chlorogenic acid, hyperoside, rutin and cyanidin 3-glucoside was evaluated in the C. elegans obese model subjected to high glucose concentrations evaluating different parameters such as lipid droplets, lipofuscin accumulation and ROS production. The capacity of the extract to inhibit advance glycation end products and free radicals as well as pancreatic lipase and α-amylase was also evaluated in vitro. The black mulberry extract showed a significant capacity to inhibit the accumulation of lipid droplets, reducing by 50.40 % the fat deposits. The extract was able to reverse the deleterious effects of excess glucose in C. elegans enhancing stress resistance, preventing the accumulation of lipofuscin, and decreasing the ROS production. The anti-glycation and antioxidant effects in vitro were higher than the reference substances aminoguanidine and quercetin respectively. Morus nigra was also able to inhibit the pancreatic enzymes α-amylase and lipase and could be considered an interesting traditional food ingredient in the prevention of certain metabolic diseases.

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.

Structures, activities, and putative biosynthetic pathways of characteristic polyphenolic compounds from Morus plants: A review

Morus plants played a pivotal role in ancient Chinese sericulture and silk production, which served as critical components of economy and culture. Besides, many parts of mulberry trees, including roots, leaves, stems, and fruits, hold various medicinal value, and have been utilized in traditional medicine for thousands of years. The chemical composition of mulberry has been reported in many literatures, while the characteristic compounds have not been systematically summarized. In this review, we focused on the polyphenolic compounds in mulberry, including flavonoids, 2-arylbenzofurans, and Diels-Alder (D-A) adducts, and summarized their structural features, structure-activity relationships, and potential biosynthetic pathways. The results revealed a characteristic class of 2'-hydroxylated flavonoids and stilbenes which played an important role in the biosynthesis of downstream 2-arylbenzofurans and D-A adducts in mulberry but had been overlooked by most studies. The prenylated modifications of different compounds were also discussed and their function as precursors of D-A adducts was emphasized. We also describe the effects of different modifications on biological activities. Besides, the chemical composition of Morus was most similar to that of Artocarpus in the Moraceae family in that they had almost identical characteristic compounds. Finally, a putative total biosynthetic pathway of D-A adducts in mulberry was proposed based on structure derivation and combination of verified reactions. This review contributes to the understanding of the biological activity and biosynthesis of the characteristic components of Morus plants.

Prenylated dihydroflavones from the root barks of Morus alba

Three new prenylated dihydroflavones, moralbaflavones A-C (1-3), together with four known ones (4a/4b, 5, and 6) were isolated from the root barks of Morus alba L. Their structures including the absolute configurations were determined by the analysis of HRMS, NMR, and ECD data. The neuroprotective properties of these prenylated dihydroflavones were screened at the concentration of 10 µM in the sodium nitroprusside-induced rat pheochromocytoma PC-12 cells, and the results showed moralbaflavone C (3) possessed significant neuroprotective activity, being more potent than the positive control edaravone.

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.

Benzofuran Derivatives from Cortex Mori Radicis and Their Cholinesterase-Inhibitory Activity

The phytochemical investigation of Cortex Mori Radicis led to the isolation and identification of a new prenylated benzofuranone (1) and four ring-opening derivatives (2-5) named albaphenol A-E, as well as nigranol A (6), together with ten 2-arylbenzofuran derivatives (7-16). The characterization of the structures of the new compounds and the structural revision of nigranol A (6) were conducted using the comprehensive analysis of spectroscopic data (1D/2D NMR, HRESIMS, CD, and XRD). Compounds 1-16 were tested for their inhibitory effects on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Compounds 1 and 4 showed weak BChE-inhibitory activity (IC50 45.5 and 61.0 μM); six 2-arylbenzofuran derivatives showed more-potent BChE-inhibitory activity (IC50 2.5-32.8 μM) than the positive control galantamine (IC50 35.3 μM), while being inactive or weakly inhibitory toward AChE. Cathafuran C (14) exhibited the most potent and selective inhibitory activity against BChE in a competitive manner, with a Ki value of 1.7 μM. The structure-activity relationships of the benzofuran-type stilbenes were discussed. Furthermore, molecular docking and dynamic simulations were performed to clarify the interactions of the inhibitor-enzyme complex.

Characterization, Antioxidant, and Antimicrobial Properties of Mulberry Lattices

In order to find the most advantageous bioactive compounds from mulberry latex for drug development in the near future, this study was conducted to characterize and evaluate antioxidant and antimicrobial properties from four different mulberry lattices (BR-2, S-1, AR-14, and S-146). The characterization of the lattices was performed by scanning electron microscopy with energy-dispersive X-ray spectroscopy, gas chromatography coupled to mass spectroscopy, and Fourier transform infrared spectroscopy. Further, screenings of the antioxidant and antimicrobial potential of selected lattices were performed in vitro using 2,2-diphenyl-1-picrylhydrazyl assay and agar well diffusion methods, respectively. Interestingly, the outcome of the current study revealed that tested mulberry lattices contain a considerable amount of bioactive phytoconstituents, particularly antimicrobial and antioxidant compounds, as revealed by chromatographic analysis. BR-2 latex was found to have significant antioxidant activity (75%) followed by S-146 (64.6%) and AR-14 (52.9%). The maximum antimicrobial activity was found in BR-2 latex compared to other tested latex varieties. The results of this investigation showed that mulberry latex from the BR-2 type may successfully control both bacterial and fungal infections, with the added benefit of having enhanced antioxidant capabilities.

Morus alba L. root decreases melanin synthesis via sphingosine-1-phosphate signaling in B16F10 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Morus alba L. has long been used for beauty in many Asian countries and regions, including anti-aging and hyperpigmentation.

AIM OF THE STUDY

This study aimed at the inhibitory effect of Morus alba L. root on melanogenesis in B16F10 melanoma cells and the mechanism involved.

MATERIALS AND METHODS

This study evaluated the anti-melanogenic effect of Morus alba L. root extract (MAR) on B16F10 melanoma cells by assessing cell viability, melanin accumulation, cellular tyrosinase activity, intra/inter-cellular S1P levels, cellular S1P-related metabolic enzyme activity, and western blot analysis. In addition, the potential S1P lyase (S1PL) inhibitory constituents in MAR were identified by LC-MS/MS.

RESULTS

Without affecting the viability of B16F10 melanoma cells, MAR inhibited intracellular tyrosinase activity in a dose-dependent manner, thereby reducing the accumulation of melanin. MAR also downregulated the expression level of MITF via activating the ERK signaling pathway. Furthermore, MAR increased the intra/inter-cellular S1P by inhibiting S1PL. Several compounds with inhibitory S1PL activity have been identified in MAR, such as mulberroside A and oxyresveratrol.

CONCLUSIONS

The anti-melanogenic effects of MAR mainly involve promoting MITF degradation mediated via S1P-S1PR3-ERK signaling through increasing cellular S1P levels by inhibiting S1PL activity.

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, MgCl2, 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 Component Kuwanon C Exerts Potent Therapeutic Efficacy In Vitro against COVID-19 by Blocking the SARS-CoV-2 Spike S1 RBD:ACE2 Receptor Interaction

There has been an immense effort by global pharmaceutical companies to develop anti-COVID-19 drugs, including small molecule-based RNA replication inhibitors via drug repositioning and antibody-based spike protein blockers related to cell entry by SARS-CoV-2. However, several limitations to their clinical use have emerged in addition to a lack of progress in the development of small molecule-based cell entry inhibitors from natural products. In this study, we tested the effectiveness of kuwanon C (KC), which has mainly been researched using in silico docking simulation and can serve as an effective building block for developing anti-COVID-19 drugs, in blocking the spike S1 RBD:ACE2 receptor interaction. KC is a natural product derived from Morus alba L., commonly known as mulberry, which has known antiviral efficacy. Molecular interaction studies using competitive ELISA and the BLItz system revealed that KC targets both the spike S1 RBD and the ACE2 receptor, successfully disrupting their interaction, as supported by the in silico docking simulation. Furthermore, we established a mechanism of action by observing how KC prevents the infection of SARS-CoV-2 spike pseudotyped virus in ACE2/TPRSS2-overexpressing HEK293T cells. Finally, we demonstrated that KC inhibits clinical isolates of SARS-CoV-2 in Vero cells. Future combinations of small molecule-based cell entry inhibitors, such as KC, with the currently prescribed RNA replication inhibitors are anticipated to significantly enhance the efficacy of COVID-19 therapies.

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).

Effects of Naphthaleneacetic Acid, Indole-3-Butyric Acid and Zinc Sulfate on the Rooting and Growth of Mulberry Cuttings

The mulberry tree (Morus alba) is a perennial and fast-growing tree distributed worldwide under different climatic conditions. Most of the world’s silk production (>90%) is facilitated by the feeding of silkworm larvae on the leaves of mulberry (Morus alba L.) varieties. Therefore, exploration of the protocol for improving the propagation efficiency and increasing the reproductive capacity of M. alba varieties could be of great significance. This study aimed to determine the effect of four concentrations (0, 100, 200 and 400 mg L−1) each of naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA), and zinc sulfate (0, 100 and 200 mg L−1), supplied separately or combined, on the rooting and growth of mulberry cuttings. M. alba cuttings were immersed for 5 s in each solution using the quick-dip method and subsequently, the cuttings were dried and planted in plastic pots and maintained in a greenhouse for 60 days. The number of leaves (NL), longest root size (LRS), longest stem size (LSS), number of rooted cuttings (NRC), number of stems per tree (NSP), rooting percentage (RP), wet root weight (WRW), dry root weight (DRW), wet stem weight (WSW), dry stem weight (DSW), wet leaf weight (WLW) and dry leaf weight (DLW) were evaluated. The results obtained showed an increase in all growth parameters of the mulberry cuttings. Treatments of hormones (IBA and NAA) and Zn sulfate were effective on LSS, LRS and WSW. The highest values of LSS were obtained for the treatments T5, T6, T14, T15, T16 and T18. Moreover, T5, T12 and T10 showed the highest values of LRS. The highest value of WSW was observed for T18, T5, T14, T15 and T16. The highest values of WLW and DLW were observed in T20 and T14. Dry stem weight (DSW) was high in T18 and T14. The application of NAA (at 200 mg L−1), IBA (200 and 400 mg L−1) and Zn sulfate (200 and 400 mg L−1), either alone or in double combination, can be a suitable and reliable method for mulberry propagation.

Anticancer and Neuroprotective Activities of Ethyl Acetate Fractions from Morus macroura Miq. Plant Organs with Ultraperformance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry Profiling

Column chromatography afforded the isolation of seven secondary metabolites (1-(2,4,6-trihydroxy phenyl)-ethanone-4-O-β-d-glucopyranoside, naringenin-7-O-β-d-glucopyranoside, kaempferol-3-O-α-l-rhamnoside, kaempferol-3-O-β-d-glucopyranoside, quercetin-3-O-β-d-glucopyranoside, quercetin-3-O-β-d-galactopyranoside, rutin) from the ethyl acetate (ET) fractions of Morus macroura Miq. stems (S), leaves (L), and fruits (F). Their identification based on ultraviolet (UV), electron ionization (EI), electrospray ionization-mass spectrometry (ESI-MS), and 1D and 2D NMR data. In addition, profiling of ET fractions using ultraperformance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) resulted in the identification of 82 compounds belonging to different classes, mainly polyphenolic constituents. Chemical profiling as well as molecular docking directed us to biological evaluation. Interestingly, the ET-L fraction exhibited a robust cytotoxic activity against HepG-2, MCF-7, and HELA cell lines. Also, it displayed a neuromodulatory activity against cisplatin neurotoxicity in rats by ameliorating the neurobehavioral dysfunction visualized in the open field and Y-maze test and modulating the neurochemical parameters such as brain amino acid levels (glutamate, aspartate, serine, and histidine), oxidative stress markers (GSH, MDA, and 8-hydroxy-2'-deoxyguanosine), and purinergic cell energy (adenosine triphosphate (ATP) and adenosine monophosphate (AMP)). In conclusion, the isolated compounds (kaempferol-3-O-β-glucoside and quercetin-3-O-β-glucoside) from the ET-L fraction could serve as potent anticancer agents due to their strong antioxidant, in vitro cytotoxicity, and in vivo neuroprotective activity.

Hepatoprotective activity of the ethanolic extract of Morus indica roots from Indian Bodo tribes

The roots of Morus species are well described in the Pharmacopoeia of the People's Republic of China (ChP) for its traditional use in treating liver fibrosis due to its hepatoprotective property. However, little is known about the hepatoprotective effect of the roots of Morus indica L. (RoMi), and the pharmacological mechanism(s) are uncertain due to its intricacy. Therefore, this study evaluates the hepatoprotective activity of the ethanolic extract of RoMi (eRoMi) against the CCl4-induced in-vivo animal model at different dosages (100 and 200 mg/kg BW) in comparison with silymarin as a positive control. The hepatoprotective activity of eRoMi was evaluated by measuring the levels of serum biomarkers, hepatic antioxidant enzymes and was verified by histological studies. Interestingly, 1,2-bis(trimethylsilyl) benzene, 1,4-phenylenebis (trimethylsilane), 2,4,6-cycloheptatriene-1-one, 3,5-bis-trimethylsilyl and α-amyrin were the active components found in eRoMi as detected by GC–MS. Oral administration of eRoMi (200 mg/kg BW) to rats significantly protected serum biochemical parameters (increased ALT, AST, LDH, bilirubin and GGT as well as depletion of antioxidant enzymes and hepatic GSH) and elevation in hepatic lipid peroxidation as compared to CCl4-treated rats. The hematological indices such as erythrocytes, hemoglobin, monocytes and lymphocytes were also normal in eRoMi-treated rats. The histopathological evaluation indicated a significant restoration of liver structure as compared to silymarin. This study is the first scientific validation for the traditional use of eRoMi to understand its hepatoprotective activity.

Hepatoprotective activity of the ethanolic extract of Morus indica roots from Indian Bodo tribes

The roots of Morus species are well described in the Pharmacopoeia of the People's Republic of China (ChP) for its traditional use in treating liver fibrosis due to its hepatoprotective property. However, little is known about the hepatoprotective effect of the roots of Morus indica L. (RoMi), and the pharmacological mechanism(s) are uncertain due to its intricacy. Therefore, this study evaluates the hepatoprotective activity of the ethanolic extract of RoMi (eRoMi) against the CCl4-induced in-vivo animal model at different dosages (100 and 200 mg/kg BW) in comparison with silymarin as a positive control. The hepatoprotective activity of eRoMi was evaluated by measuring the levels of serum biomarkers, hepatic antioxidant enzymes and was verified by histological studies. Interestingly, 1,2-bis(trimethylsilyl) benzene, 1,4-phenylenebis (trimethylsilane), 2,4,6-cycloheptatriene-1-one, 3,5-bis-trimethylsilyl and α-amyrin were the active components found in eRoMi as detected by GC–MS. Oral administration of eRoMi (200 mg/kg BW) to rats significantly protected serum biochemical parameters (increased ALT, AST, LDH, bilirubin and GGT as well as depletion of antioxidant enzymes and hepatic GSH) and elevation in hepatic lipid peroxidation as compared to CCl4-treated rats. The hematological indices such as erythrocytes, hemoglobin, monocytes and lymphocytes were also normal in eRoMi-treated rats. The histopathological evaluation indicated a significant restoration of liver structure as compared to silymarin. This study is the first scientific validation for the traditional use of eRoMi to understand its hepatoprotective activity.

Bioguided isolation, identification and bioactivity evaluation of anti-MRSA constituents from Morus alba Linn

ETHNOPHARMACOLOGY RELEVANCE

The root bark of Morus alba Linn. (M. alba), a traditional folk medicine, has been documented in the Chinese Pharmacopoeia, which has been widely used for asthma, fever, pneumonia, edema, vomit, colitis, bronchitis and keratitis diseases. Some of the diseases may be related to respiratory, digestive, urinary tract infections. Although Diels-Alder adducts (DAAs), flavonoids, 2-arylbenzofurans and stilbene compounds have been isolated from the root bark of M. alba, few compounds are reported for their antimicrobial efficacy in vivo and the mechanism.

AIM OF THE STUDY

The aim of the study was to isolate and identify compounds of the root bark of M. alba in view of their anti-MRSA bioactivity, evaluate the anti-MRSA bioactivity of compounds and 60% ethanol elution (MA-6) in vitro and in vivo, and explore preliminary antibacterial mechanism in order to provide natural resources against MRSA infection.

MATERIALS AND METHODS

Systematic phytochemical investigations were carried out according to the thin layer chromatography (TLC) of the active fraction MA-6 to find more anti-MRSA ingredients. The compounds of the root bark of M. alba were separated by column chromatography and identified by LC-MS/MS and NMR spectroscopy. The anti-MRSA efficacy of the active ingredients were evaluated by broth microdilution method and a murine infection model. The mode of action of compounds was explored by time-kill curve and post-contact effect. The preliminary mechanism of compounds against MRSA was explored by drug efflux pumps and bacterial biofilms.

RESULTS

Chemical isolation resulted in twenty-nine known compounds, most with one or more geranyl and prenyl units exhibited superior anti-MRSA bioactivity, with MIC values of 2-16 μg/mL. In addition, the mode of action indicated that compounds presented persistent antimicrobial effect, which also produced concentration-dependent and time-dependent killing activity or property. Preliminary mechanism showed that the compound kuwanon O (29) damaged the bacterial cell membranes, leading to the accumulation of antibiotics inside bacterial cells, moreover, MA-6 and kuwanon O (29) inhibited the efflux of drugs by combining with methicillin or ethidium bromide (EtBr), resulting in the MICs of EtBr and methicillin were obviously decreased three-fold. The anti-MRSA efficacy in vivo indicated that the active fraction MA-6 could reduce bacteria in spleen, liver, kidney and mortality of acutely infectious mice, which was better than the positive drug berberine chloride.

CONCLUSION

Experimental investigation showed that the MA-6 and compound 29 have promising bioactivity against MRSA in vitro and in vivo, which might be used as a potential source of new antibacterial medicine or a potential efflux pump inhibitor against MRSA infection.

Do Uncommon Plant Phenolic Compounds Have Uncommon Properties? A Mini Review on Novel Flavonoids

Unique plants and their properties, once considered synonymous to medicine, remain a potent source for new compounds in modern science. Plant polyphenols and natural products continue to be investigated for effective treatments for the most persistent of human ailments. In this review, fifty novel plant phenolic compounds have been compiled and briefly described from the previous five years. Select compounds and notable plant species from genus Morinda and Sophora are further expanded on. Traditional medicine plants often contain rich and diverse mixtures of flavonoids, from which rare compounds should receive attention. The bioactivity of crude plant extracts, purified compounds and mixtures can differ greatly, requiring that these interactions and mechanisms of action be investigated in greater detail. Novel applications of uncommon natural products, namely mimosine and juglone, are explored within this review. The 2019 coronavirus pandemic has resulted in abrupt spike of related scientific publications: speculation is made regarding plant natural products and future of antiviral drug discovery.

Rearranged Diels-Alder Adducts and Prenylated Flavonoids as Potential PTP1B Inhibitors from Morus nigra

Two novel rearranged Diels-Alder adducts, morunigrines A (1) and B (2), and four new prenylated flavonoids, morunigrols A-D (3-6), were isolated from the twigs of Morus nigra, together with four known prenylated phenolic compounds, including two flavonoids (7 and 8) and two 2-arylbenzofurans (9 and 10). Morunigrines A (1) and B (2) are a novel class of Diels-Alder adducts with unprecedented carbon skeletons featuring a rearranged chalcone-stilbene/2-arylbenzofuran core decorated with a unique methylbiphenyl moiety. The structures of the new compounds were assigned by analysis of spectroscopic data. The absolute configuration of compound 6 was determined by the measurement of specific rotation. A plausible biogenetic pathway for 1 and 2 is also proposed. Compounds 1 and 2 exhibited more potent protein tyrosine phosphatase 1B inhibitory activity with IC₅₀ values of 1.8 ± 0.2 and 1.3 ± 0.3 μM, respectively, than that of the positive control oleanolic acid (IC₅₀, 2.5 ± 0.1 μM).

IN-SILICO dynamic analysis of Sulawesi propolis as anti-endometriosis drug: Interaction study with TNF alpha receptor, NF-kB, estrogen receptor, progesterone receptor and prostaglandin receptor

INTRODUCTION

Endometriosis is a disease that impacts around 10% of all women in reproductive age, with pelvic pain and infertility as its main clinical features. Current medical treatment targeting lowering estrogen activity has not shown sufficient result due its side effects and reproductive function suppression. Propolis has been widely studied, showing anti inflammation and pro-apoptosis property, that could potentially be used in the treatment of endometriosis. This study investigates the interaction between Sulawesi Propolis' active components and receptors and protein related to endometriosis pathogenesis.

METHODS

Active components of Sulawesi Propolis were initially identified with their targeted protein receptors. Lipinski rules were used to screen potential components. The ligands and proteins were tested using Autodock program to predict the most active compound and possible binding sites between propolis and some target proteins associated with inflammatory and apoptotic activity in endometriosis models. Receptor modelling is then performed using Swiss-Model.

RESULTS

These active components of Sulawesi Propolis showed a strong binding potential towards TNF- α, NF-kb, Estrogen-α, Estrogen-β, progesterone B, PGE2 EP2 and EP3 subtype respectively: Sanggenon C, Sanggenon H, Epicryptoacetalide, Chrysin-7-O-β-D-glucopyranodside, Irilone, Polydatin and Epicryptoacetalide. Compared to its negative ligand, Sulawesi Propolis displayed a stronger binding capacity to TNF-α, Estrogen-α, and Progesterone B receptors.

CONCLUSION

Sulawesi Propolis has the ability to interact with receptors related to reproductive function, apoptotic reactions and inflammatory processes, a significant factor associated with the pathogenesis of endometriosis.

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.

Evaluation of Selective COX-2 Inhibition and In Silico Study of Kuwanon Derivatives Isolated from Morus alba

Six kuwanon derivatives (A/B/C/E/H/J) extracted from the roots of Morus alba L. were evaluated to determine their cyclooxygenase (COX)-1 and 2 inhibitory effects. Cyclooxygenase (COX) is known as the target enzyme of nonsteroidal anti-inflammatory drugs (NSAIDs), which are the most widely used therapeutic agents for pain and inflammation. Among six kuwanon derivatives, kuwanon A showed selective COX-2 inhibitory activity, almost equivalent to that of celecoxib, a known COX inhibitor. Kuwanon A showed high COX-2 inhibitory activity (IC₅₀ = 14 μM) and a selectivity index (SI) range of >7.1, comparable to celecoxib (SI > 6.3). To understand the mechanisms underlying this effect, we performed docking simulations, fragment molecular orbital (FMO) calculations, and pair interaction energy decomposition analysis (PIEDA) at the quantum-mechanical level. As a result, kuwanon A had the strongest interaction with Arg120 and Tyr355 at the gate of the COX active site (−7.044 kcal/mol) and with Val89 in the membrane-binding domain (−6.599 kcal/mol). In addition, kuwanon A closely bound to Val89, His90, and Ser119, which are residues at the entrance and exit routes of the COX active site (4.329 Å). FMO calculations and PIEDA well supported the COX-2 selective inhibitory action of kuwanon A. It showed that the simulation and modeling results and experimental evidence were consistent.

Ethnobotany and the Role of Plant Natural Products in Antibiotic Drug Discovery

The crisis of antibiotic resistance necessitates creative and innovative approaches, from chemical identification and analysis to the assessment of bioactivity. Plant natural products (NPs) represent a promising source of antibacterial lead compounds that could help fill the drug discovery pipeline in response to the growing antibiotic resistance crisis. The major strength of plant NPs lies in their rich and unique chemodiversity, their worldwide distribution and ease of access, their various antibacterial modes of action, and the proven clinical effectiveness of plant extracts from which they are isolated. While many studies have tried to summarize NPs with antibacterial activities, a comprehensive review with rigorous selection criteria has never been performed. In this work, the literature from 2012 to 2019 was systematically reviewed to highlight plant-derived compounds with antibacterial activity by focusing on their growth inhibitory activity. A total of 459 compounds are included in this Review, of which 50.8% are phenolic derivatives, 26.6% are terpenoids, 5.7% are alkaloids, and 17% are classified as other metabolites. A selection of 183 compounds is further discussed regarding their antibacterial activity, biosynthesis, structure-activity relationship, mechanism of action, and potential as antibiotics. Emerging trends in the field of antibacterial drug discovery from plants are also discussed. This Review brings to the forefront key findings on the antibacterial potential of plant NPs for consideration in future antibiotic discovery and development efforts.

Improvement of stilbene production by mulberry Morus alba root culture via precursor feeding and co-elicitation

Large amounts of Morus alba L. (MA) roots are needed as the source of active stilbenes in the industrial production of traditional medicines and cosmeceuticals. A recent investigation demonstrated resveratrol and its derivatives to be promising anti-COVID-19 agents. However, conventional cultivation of MA does not meet the demand for its stilbenes, and root quality usually varies between crops. This study established the in vitro non-GMO root culture of MA and optimized the root density, precursor feeding, and elicitors for stilbene productivity. A root culture with optimal inoculum density (3 g/flask of 30 mL medium) accumulated mulberroside A, oxyresveratrol, and resveratrol at 18.7 ± 1.00 mg/g, 136 ± 5.05 µg/g, and 41.6 ± 5.84 µg/g dry weight (DW), respectively. The feeding of L-tyrosine shortened the time required to reach the stilbene productive stage. Root cultures co-treated with 200 µM methyl jasmonate and 2 mg/mL yeast extract accumulated the highest contents of mulberroside A (30.3 ± 2.68 mg/g DW), oxyresveratrol (68.6 ± 3.53 µg/g DW), and resveratrol (10.2 ± 0.53 µg/g DW). In summary, root culture is a promising and sustainable source of stilbenes for the development of health products and agents for further investigation as potential anti-COVID-19 agents.

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.

Clearing heat and resolving phlegm for acute exacerbation of chronic obstructive pulmonary disease with the syndrome of phlegm-heat obstruction of the lung

Objective

This study aimed to evaluate the effect of clearing heat and resolving phlegm for acute exacerbation of chronic obstructive pulmonary disease with the syndrome of phlegm-heat obstruction of the lung.

Methods

This was a real-world retrospective cohort study of inpatients at our institution from 1 January 2015 to 31 December 2017. The patients were divided into two groups according to whether they received oral traditional Chinese medicine (TCM) for clearing heat and resolving phlegm or routine treatment (controls). Efficacy and safety indicators were analyzed. Propensity score matching was used to control for confounding factors.

Results

Among 488 patients, 164 (82 pairs) were successfully matched. The changes in neutrophils (%) and C-reactive protein levels were more significant in the TCM group than in the control group. The duration of fever was significantly shorter in the TCM group than in the control group.

Conclusions

The therapy of clearing heat and resolving phlegm might effectively control the inflammatory reaction of acute exacerbation of chronic obstructive pulmonary disease in patients with the syndrome of phlegm-heat obstruction of the lung, especially for those with fever. Nevertheless, large-scale and prospective studies are required to provide a higher quality of evidence.

Food as medicine: A possible preventive measure against coronavirus disease (COVID-19)

The recent and ongoing outbreak of coronavirus disease (COVID‐19) is a huge global challenge. The outbreak, which first occurred in Wuhan City, Hubei Province, China and then rapidly spread to other provinces and to more than 200 countries abroad, has been declared a global pandemic by the World Health Organization. Those with compromised immune systems and/or existing respiratory, metabolic or cardiac problems are more susceptible to the infection and are at higher risk of serious illness or even death. The present review was designed to report important functional food plants with immunomodulatory and anti‐viral properties. Data on medicinal food plants were retrieved and downloaded from English‐language journals using online search engines. The functional food plants herein documented might not only enhance the immune system and cure respiratory tract infections but can also greatly impact the overall health of the general public. As many people in the world are now confined to their homes, inclusion of these easily accessible plants in the daily diet may help to strengthen the immune system and guard against infection by SARS‐CoV‐2. This might reduce the risk of COVID‐19 and initiate a rapid recovery in cases of SARS‐CoV‐2 infection.

Advances on Antiviral Activity of Morus spp. Plant Extracts: Human Coronavirus and Virus-Related Respiratory Tract Infections in the Spotlight

(1) Background: Viral respiratory infections cause life-threatening diseases in millions of people worldwide every year. Human coronavirus and several picornaviruses are responsible for worldwide epidemic outbreaks, thus representing a heavy burden to their hosts. In the absence of specific treatments for human viral infections, natural products offer an alternative in terms of innovative drug therapies. (2) Methods: We analyzed the antiviral properties of the leaves and stem bark of the mulberry tree (Morus spp.). We compared the antiviral activity of Morus spp. on enveloped and nonenveloped viral pathogens, such as human coronavirus (HCoV 229E) and different members of the Picornaviridae family-human poliovirus 1, human parechovirus 1 and 3, and human echovirus 11. The antiviral activity of 12 water and water-alcohol plant extracts of the leaves and stem bark of three different species of mulberry-Morus alba var. alba, Morus alba var. rosa, and Morus rubra-were evaluated. We also evaluated the antiviral activities of kuwanon G against HCoV-229E. (3) Results: Our results showed that several extracts reduced the viral titer and cytopathogenic effects (CPE). Leaves' water-alcohol extracts exhibited maximum antiviral activity on human coronavirus, while stem bark and leaves' water and water-alcohol extracts were the most effective on picornaviruses. (4) Conclusions: The analysis of the antiviral activities of Morus spp. offer promising applications in antiviral strategies.

The emerging role of paraptosis in tumor cell biology: Perspectives for cancer prevention and therapy with natural compounds

Standard anti-cancer therapies promote tumor growth suppression mainly via induction of apoptosis. However, in most cases cancer cells acquire the ability to escape apoptotic cell death, thus becoming resistant to current treatments. In this setting, the interest in alternative cell death modes has recently increased. Paraptosis is a new form of programmed cell death displaying endoplasmic reticulum (ER) and/or mitochondria dilation, generally due to proteostasis disruption or redox and ion homeostasis alteration. Recent studies have highlighted that several natural compounds can trigger paraptosis in different tumor cell lines. Here, we review the molecular mechanisms underlying paraptotic cell death, as well as the natural products inducing this kind of cell death program. A better understanding of paraptosis should facilitate the development of new therapeutic strategies for cancer prevention and treatment.

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, D_2LR, 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/D_2LR 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/D_2LR 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 D_2LR 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/D_2LR 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).

Prenylated Stilbenoids Affect Inflammation by Inhibiting the NF-κB/AP-1 Signaling Pathway and Cyclooxygenases and Lipoxygenase

Stilbenoids are important components of foods (e.g., peanuts, grapes, various edible berries), beverages (wine, white tea), and medicinal plants. Many publications have described the anti-inflammatory potential of stilbenoids, including the widely known trans-resveratrol and its analogues. However, comparatively little information is available regarding the activity of their prenylated derivatives. One new prenylated stilbenoid (2) was isolated from Artocarpus altilis and characterized structurally based on 1D and 2D NMR analysis and HRMS. Three other prenylated stilbenoids were prepared synthetically (9-11). Their antiphlogistic potential was determined by testing them together with known natural prenylated stilbenoids from Macaranga siamensis and Artocarpus heterophyllus in both cell-free and cell assays. The inhibition of 5-lipoxygenase (5-LOX) was also shown by simulated molecular docking for the most active stilbenoids in order to elucidate the mode of interaction between these compounds and the enzyme. Their effects on the pro-inflammatory nuclear factor-κB (NF-κB) and the activator protein 1 (AP-1) signaling pathway were also analyzed. The THP1-XBlue-MD2-CD14 cell line was used as a model for determining their anti-inflammatory potential, and lipopolysaccharide (LPS) stimulation of Toll-like receptor 4 induced a signaling cascade leading to the activation of NF-κB/AP-1. The ability of prenylated stilbenoids to attenuate the production of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) was further evaluated using LPS-stimulated THP-1 macrophages.

Protective effect of Mori Cortex radicis extract against high glucose-induced oxidative stress in PC12 cells

This study was undertaken to investigate the neuroprotective effect of an ethanolic extract of Mori Cortex radicis (MCR) against high glucose (HG)-induced oxidative damage in PC12 cells. Cell cytotoxicity was examined using MTT and lactate dehydrogenase assays. To examine the antioxidative effects, intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) levels and the activities of antioxidant enzymes were measured. The expressions of apoptosis-associated proteins were assessed. MCR was found to increase the viabilities of HG-induced PC12 cells and to inhibit ROS and MDA production and to promote antioxidative enzyme activities. Furthermore, MCR reduced apoptosis by upregulating p-Akt and Bcl-2/Bax ratio and reducing cytochrome c level. The main flavonoids in MCR were identified by HPLC to be kuwanon G and morusin. These results suggest the antioxidative effects of MCR protect against HG-induced oxidative stress and that MCR has potential therapeutic use for the prevention and treatment of diabetic neuro-degeneration.

Arylbenzofurans from the Root Bark of Morus alba as Triple Inhibitors of Cholinesterase, β-Site Amyloid Precursor Protein Cleaving Enzyme 1, and Glycogen Synthase Kinase-3β: Relevance to Alzheimer's Disease

Cholinesterase, β-site amyloid precursor protein cleaving enzyme 1 (BACE1), and glycogen synthase kinase-3β (GSK-3β) are the three main enzymes responsible for the early onset of Alzheimer's disease (AD). The main aim of the present study was to delineate and accentuate the triple-inhibitory potential of arylbenzofurans from Morus alba against these enzymes. Overall, the enzyme inhibition assays demonstrated the prominence of mulberrofuran D2 as an inhibitor of AChE, BChE, BACE1, and GSK-3β enzymes with IC₅₀ values of 4.61, 1.51, 0.73, and 6.36 μM, respectively. Enzyme kinetics revealed different modes of inhibition, and in silico modeling suggested that mulberrofuran D2 inhibited these enzymes with low binding energy through hydrophilic, hydrophobic, and π-cation interactions in the active site cavities. Similarly, in Aβ-aggregation assays, mulberrofuran D2 inhibited self-induced and AChE-induced Aβ aggregation in a concentration-dependent manner that was superior to reference drugs. These results suggest that arylbenzofurans from M. alba, especially mulberrofuran D2, are triple inhibitors of cholinesterase, BACE1, and GSK-3β and may represent a novel class of anti-AD drugs.

Mulberry Bark Alleviates Effect of STZ Inducing Diabetic Mice through Negatively Regulating FoxO1

Dysfunction of insulin secretion and hyperglycaemia were commonly found due to damaged β cells of pancreas. In our previous research, it was found that mulberry branch bark powder (MBBP) was effective in treating diabetes in mice which were induced by STZ and high fat diet. The present study was designed to evaluate the protective effect of MBBP on STZ-induced β cells injury and investigate underlying mechanisms. By preventive administration of branch bark powder, the damage caused by STZ injection was found to be alleviated. In MBBP feed groups, pathological weight loss was inhibited, fasting blood glucose was controlled, the incidence of diabetes decreased, and blood lipid level and antioxidant capacities were restored. The PI3K/AKT/FoxO1 signal pathway was found to be activated by key proteins expression and gene testing. In liver, the increased PI3K and phosphorylated AKT, the phosphorylated, and inactivated FoxO1, which regulates the expression of gluconeogenic gene and explains the effect of relieving insulin resistance of MBBP. Therefore, the MBBP improves the tolerance of pancreas to the toxicity of STZ involving the PI3K/AKT/FoxO1 signalling pathway.

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.

Anti-inflammatory and preventive activity of white mulberry root bark extract in an experimental model of pancreatitis

Pancreatitis is characterized by highly morbid inflammation in the pancreas. Currently, there is no specific drug available for pancreatitis except supportive medicines. The present study assessed the pancreato-protective effect of Morus alba root bark extract by using alcohol and cerulein-induced model of pancreatitis. The study also investigated the phytochemical profile through GC-MS and HPLC. Methanolic extract of Morus alba root bark extract (MEMARB) was subjected to GC-MS and HPLC studies. Male albino Wistar rats were administered ethanol (0%-36%) and cerulein (20 μg/kg b.wt. i.p.) with or without MEMARB. Serum lipase, amylase, caspase-1, lipid peroxidation products, glutathione and enzymatic antioxidants were determined. Histological changes in the pancreas were assessed. Cudraflavone B in MEMARB was quantified by HPLC. Significant amount of Cudraflavone B was detected by quantitative HPLC. Marked increase in the levels of serum amylase, lipase, caspase-1, IL-18 and IL-1β were observed in ethanol and cerulein administered rats than in MEMARB co-administered rats. In MEMARB co-administered rats, the antioxidant status was restored to near normal levels. Histological examinations showed that MEMARB significantly reduced the inflammatory and fibrotic changes. The results reveal the potent pancreato-protective effects of Morus alba root bark. The anti-inflammatory effect of Morus alba root bark extract might be due to the presence of various phytonutrients including Cudraflavone B.

Quadruple high-resolution α-glucosidase/α-amylase/PTP1B/radical scavenging profiling combined with high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy for identification of antidiabetic constituents in crude root bark of Morus alba L

In this paper, quadruple high-resolution α-glucosidase/α-amylase/PTP1B/radical scavenging profiling combined with HPLC-HRMS-SPE-NMR were used for studying the polypharmacological properties of crude root bark extract of Morus alba L. This species is used as an anti-diabetic principle in many traditional treatment systems around the world, and the crude ethyl acetate extract of M. alba root bark was found to inhibit α-glucosidase, α-amylase and protein-tyrosine phosphatase 1B (PTP1B) with IC₅₀ values of 1.70 ± 0.72, 5.16 ± 0.69, and 5.07 ± 0.68 μg/mL as well as showing radical scavenging activity equaling a TEAC value of (3.82 ± 0.14) × 10⁴ mM per gram extract. Subsequent investigation of the crude extract using quadruple high-resolution α-glucosidase/α-amylase/PTP1B/radical scavenging profiling provided a quadruple biochromatogram that allowed direct correlation of the HPLC peaks with one or more of the tested bioactivities. This was used to target subsequent HPLC-HRMS-SPE-NMR analysis towards peaks representing bioactive analytes, and led to identification of a new Diels-Alder adduct named Moracenin E as well as a series of Diels-Alder adducts and isoprenylated flavonoids as potent α-glucosidase and α-amylase inhibitors with IC₅₀ values in the range of 0.60-27.15 μM and 1.22-69.38 μM, respectively. In addition, these compounds and two 2-arylbenzofurans were found to be potent PTP1B inhibitors with IC₅₀ values ranging from 4.04 to 21.67 μM. The high-resolution radical scavenging profile also revealed that almost all of the compounds possess radical scavenging activity. In conclusion the quadruple high-resolution profiling method presented here allowed a detailed profiling of individual constituents in crude root bark extract of M. alba, and the method provides a general tool for detailed mapping of bioactive constituents in polypharmacological herbal remedies.

Prenylated flavonoids as potent phosphodiesterase-4 inhibitors from Morus alba: Isolation, modification, and structure-activity relationship study

The bioassay-guided phytochemical study of a traditional Chinese medicine Morus alba led to the isolation of 18 prenylated flavonoids (1-18), of which (±)-cyclomorusin (1/2), a pair of enantiomers, and 14-methoxy-dihydromorusin (3) are the new ones. Subsequent structural modification of the selected components by methylation, esterification, hydrogenation, and oxidative cyclization led to 14 more derivatives (19-32). The small library was screened for its inhibition against phosphodiesterase-4 (PDE4), which is a drug target for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Among them, nine compounds (1-5, 8, 10, 16, and 17) exhibited remarkable activities with IC₅₀ values ranging from 0.0054 to 0.40 μM, being more active than the positive control rolipram (IC₅₀ = 0.62 μM). (+)-Cyclomorusin (1), the most active natural PDE4 inhibitor reported so far, also showed a high selectivity across other PDE members with the selective fold greater than 55. The SAR study revealed that the presence of prenyls at C-3 and/or C-8, 2H-pyran ring D, and the phenolic hydroxyl groups were important to the activity, which was further supported by the recognition mechanism study of the inhibitors with PDE4 by using molecular modeling.