Anti-inflammatory activity of mulberrofuran K isolated from the bark of Morus bombycis

Total Synthesis and Antibacterial Evaluation of Lupinifolin and Its Natural Analogues

In this study, lupinifolin (1) and its natural analogues, mundulin (2), minimiorin (3), khonklonginol H (4), flemichin D (5), and eriosemaone A (27), were obtained by chemical synthesis for the first time. Key steps involved an electrocyclization to build the linear pyran rings and a Claisen/Cope rearrangement to install the 8-prenyl substituents. All compounds were assessed for their in vitro antimicrobial activities against clinically relevant human pathogens, including one Gram-negative bacterial strain (E. coli ATCC 25922) and four Gram-positive bacterial strains (S. aureus ATCC 29213, E. faecalis ATCC 29212, MRSA21-5, and VRE ATCC 51299). The result indicated that eriosemaone A (27) was the most potent one against Gram-positive bacteria, with minimum inhibitory concentrations in the range of 0.25-0.5 μg/mL. Mechanistic studies indicated that 27 has good membrane-targeting ability to bacterial inner membranes and can bind to phosphatidylglycerol and cardiolipin in bacterial membranes, thereby disrupting the bacterial cell membranes and causing bacterial death.

Synergistic effect of constituent drugs of Baibutang on improving Yin-deficiency pulmonary fibrosis in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Baibutang (BBT) is an ancient prescription for the treatment of pulmonary fibrosis. Previous experiments have shown that BBT had a good therapeutic effect on pulmonary fibrosis. However, there had been no study on the synergy between drugs composed of BBT. Due to the interaction between the constituent drugs, exploring their synergy profile is of great significance for explaining the essence of BBT's efficacy in improving pulmonary fibrosis.

AIM OF THE STUDY

Based on the pharmacodynamic value, this study aimed to explore a method for the evaluation of the synergy profile between constituent drugs in traditional Chinese medicine (TCM) compounds.

MATERIALS AND METHODS

Nine herbs of BBT were divided into Zhikeqingre (ZK), Yangyinyiqi (YY) and Lishijianpi (LS) groups. A rat model of Yin-deficiency pulmonary fibrosis induced by thyroxine-bleomycin was used to evaluate the effects of BBT and the three groups. The pathological changes of lung tissue and the changes of biomarkers associated with fibrosis, Yin-deficiency and water-fluid metabolism were detected. After standardization of pharmacodynamics value (PV), the compatibility coefficient (CC) of the three groups, the relative PV (RPV) and contribution value (CV) of each group on every index were calculated.

RESULTS

The average CC on fibrosis indexes was 0.44, indicating that 44% of the efficacy of BBT came from the synergistic effect of the three groups. ZK group had the highest RPV (0.80) in improving fibrosis indexes such as histopathological changes, α-SMA, collagen-I and renin-angiotensin system. The average CC on Yin-deficiency indexes was 0.25, and YY group had the highest RPV (0.96) in improving deficiency indexes such as body temperature, cAMP/cGMP ratio, and PDEs, PGE2 and COX-2 levels. The average CC on water-fluid metabolism indexes was 0.15, and LS group had the highest RPV (1.52) in improving water-fluid metabolism indexes such as aquaporins, mucins, and surfactant proteins. The results also showed that 29% of the improvement effect of BBT on all indexes came from the synergistic effect of the three groups, and the contribution of ZK, YY and LS groups to the efficacy of BBT were 25%, 25% and 21%, respectively.

CONCLUSION

The established semiquantitative method can clearly and simply evaluate the synergy of the three groups in BBT, which will help to promote the research on the synergy of TCM compounds and other multiple-components combinations.

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.

Identification of natural compounds as SARS-CoV-2 inhibitors via molecular docking and molecular dynamic simulation

Background

Base mutations increase the contagiousness and transmissibility of the Delta and Lambda strains and lead to the severity of the COVID-19 pandemic. Molecular docking and molecular dynamics (MD) simulations are frequently used for drug discovery and relocation. Small molecular compounds from Chinese herbs have an inhibitory effect on the virus. Therefore, this study used computational simulations to investigate the effects of small molecular compounds on the spike (S) protein and the binding between them and angiotensin-converting enzyme 2 (ACE2) receptors.

Methods

In this study, molecular docking, MD simulation, and protein-protein analysis were used to explore the medicinal target inhibition of Chinese herbal medicinal plant chemicals on SARS-CoV-2. 12,978 phytochemicals were screened against S proteins of SARS-CoV-2 Lambda and Delta mutants.

Results

Molecular docking showed that 65.61% and 65.28% of the compounds had the relatively stable binding ability to the S protein of Lambda and Delta mutants (docking score ≤ -6). The top five compounds with binding energy with Lambda and Delta mutants were clematichinenoside AR2 (-9.7), atratoglaucoside,b (-9.5), physalin b (-9.5), atratoglaucoside, a (-9.4), Ochnaflavone (-9.3) and neo-przewaquinone a (-10), Wikstrosin (-9.7), xilingsaponin A (-9.6), ardisianoside G (-9.6), and 23-epi-26-deoxyactein (-9.6), respectively. Four compounds (Casuarictin, Heterophylliin D, Protohypericin, and Glansrin B) could interact with S protein mutation sites of Lambda and Delta mutants, respectively, and MD simulation results showed that four plant chemicals and spike protein have good energy stable complex formation ability. In addition, protein-protein docking was carried out to evaluate the changes in ACE2 binding ability caused by the formation of four plant chemicals and S protein complexes. The analysis showed that the binding of four plant chemicals to the S protein could reduce the stability of the binding to ACE2, thereby reducing the replication ability of the virus.

Conclusion

To sum up, the study concluded that four phytochemicals (Casuarictin, Heterophylliin D, Protohypericin, and Glansrin B) had significant effects on the binding sites of the SARS-CoV-2 S protein. This study needs further in vitro and in vivo experimental validation of these major phytochemicals to assess their potential anti-SARS-CoV-2. Graphical abstract.

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).

Molecular modelling studies and identification of novel phytochemical inhibitor of DLL3

Prostate cancer has been recently considered the most diagnosed cancer in male. DLL3 is overexpressed in CRPC-NE but not in localised prostate cancer or BPH. There are no effective treatments for neuroendocrine differentiated prostate cancer due to a lack of understanding of DLL3 structure and function. The structure of DLL3 is not yet determined using any experimental techniques. Hence, the structure-based drug discovery approach against prostate cancer has not shown great success. In present study, molecular modelling techniques were employed to generate three-dimensional structure of DLL3 and performed its thorough structural analysis. Further, all-atom molecular dynamics simulation was performed to obtain energetically favourable conformation. Further, we used a virtual screening using a library of >13800 phytochemicals from the IMPPAT database and other literature to select the best possible phytochemical inhibitor for DLL3 and identified the top five compounds. Relative binding affinity was calculated using the MM-PBSA approach. ADMET properties of the screened compounds reveal the toxic effect of Gnemonol C. We believe these studied physicochemical properties, functional domain identification, and binding site identification would be very useful to gain more structural and functional insights of DLL3; also, it can be used to infer their pharmacodynamics properties of DLL3 which was recently reported as an important prostate cancer target. The current study also proposes that Ergosterol Peroxide, Dioslupecin A, Mulberrofuran K, and Caracurine V have strong affinities and could serve as plausible inhibitors against DLL3. We believe this study would further help develop better drug candidates against neuroendocrine prostate cancer.Communicated by Ramaswamy H. Sarma.

A review of alpha-glucosidase inhibitors from plants as potential candidates for the treatment of type-2 diabetes

Diabetes mellitus is a multifactorial global health disorder that is rising at an alarming rate. Cardiovascular diseases, kidney damage and neuropathy are the main cause of high mortality rates among individuals with diabetes. One effective therapeutic approach for controlling hyperglycemia associated with type-2 diabetes is to target alpha-amylase and alpha-glucosidase, enzymes that catalyzes starch hydrolysis in the intestine. At present, approved inhibitors for these enzymes are restricted to acarbose, miglitol and voglibose. Although these inhibitors retard glucose absorption, undesirable gastrointestinal side effects impede their application. Therefore, research efforts continue to seek novel inhibitors with improved efficacy and minimal side effects. Natural products of plant origin have been a valuable source of therapeutic agents with lesser toxicity and side effects. The anti-diabetic potential through alpha-glucosidase inhibition of plant-derived molecules are summarized in this review. Eight molecules (Taxumariene F, Akebonoic acid, Morusin, Rhaponticin, Procyanidin A2, Alaternin, Mulberrofuran K and Psoralidin) were selected as promising drug candidates and their pharmacokinetic properties and toxicity were discussed where available.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11101-021-09773-1.

α‑rhamnrtin‑3‑α‑rhamnoside exerts anti‑inflammatory effects on lipopolysaccharide‑stimulated RAW264.7 cells by abrogating NF‑κB and activating the Nrf2 signaling pathway

α-rhamnrtin-3-α-rhamnoside (ARR) is the principal compound extracted from Loranthus tanakae Franch. & Sav. However, its underlying pharmacological properties remain undetermined. Inflammation is a defense mechanism of the body; however, the excessive activation of the inflammatory response can result in physical injury. The present study aimed to investigate the effects of ARR on lipopolysaccharide (LPS)-induced RAW264.7 macrophages and to determine the underlying molecular mechanism. A Cell Counting Kit-8 assay was performed to assess cytotoxicity. Nitric oxide (NO) production was measured via a NO colorimetric kit. Levels of prostaglandin E2 (PGE₂) and proinflammatory cytokines, IL-1β and IL-6, were detected using ELISAs. Reverse transcription-quantitative (RT-q)PCR analysis was performed to detect the mRNA expression levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), IL-6 and IL-1β in LPS-induced RAW246.7 cells. Western blotting, immunofluorescence and immunohistochemistry analyses were performed to measure the expression levels of NF-κB and nuclear factor-erythroid 2-related factor 2 (Nrf2) signaling pathway-related proteins to elucidate the molecular mechanisms of the inflammatory response. The results of the cytotoxicity assay revealed that doses of ARR ≤200 µg/ml exhibited no significant effect on the viability of RAW264.7 cells. The results of the Griess assay demonstrated that ARR inhibited the production of NO. In addition, the results of the ELISAs and RT-qPCR analysis discovered that ARR reduced the production of the proinflammatory cytokines, IL-1β and IL-6, as well as the proinflammatory mediators, PGE₂, iNOS and COX-2, in LPS-induced RAW264.7 cells. Immunohistochemical analysis demonstrated that ARR inhibited LPS-induced activation of TNF-associated factor 6 (TRAF6) and NF-κB p65 signaling molecules, while reversing the downregulation of the NOD-like receptor family CARD domain containing 3 (NLRC3) signaling molecule, which was consistent with the results of the western blotting analysis. Immunofluorescence results indicated that ARR reduced the increase of NF-κB p65 nuclear expression induced by LPS. Furthermore, the results of the western blotting experiments also revealed that ARR upregulated heme oxygenase-1, NAD(P)H quinone dehydrogenase 1 and Nrf2 pathway molecules. In conclusion, the results of the present study suggested that ARR may exert anti-inflammatory effects by downregulating NF-κB and activating Nrf2-mediated inflammatory responses, suggesting that ARR may be an attractive anti-inflammatory candidate drug.

Antioxidant evaluation-guided chemical profiling and structure-activity analysis of leaf extracts from five trees in Broussonetia and Morus (Moraceae)

Morus and Broussonetia trees are widely used as food and/or feed. Among 23 phenolics identified from leaves of five Moraceae species using UPLC–QTOF–MS/MS, 15 were screened using DPPH/ABTS-guided HPLCs, including seven weak (flavonoids with one hydroxyl on B-ring) and eight strong (four caffeoylquinic acids and four flavonoids, each with a double hydroxyl on B-ring) antioxidants. We then determined the activity and synergistic effects of individual antioxidants and a mixture of the eight strongest antioxidants using DPPH-guided HPLC. Our findings revealed that (1) flavonoid glucuronide may have a more negative effect on antioxidant activity than glucoside, and (2) other compounds in the mixture may exert a negative synergistic effect on antioxidant activity of the four flavonoids with B-ring double hydroxyls but not the four caffeoylquinic acids. In conclusion, the eight phenolics with the strongest antioxidant ability reliably represented the bioactivity of the five extracts examined in this study. Moreover, the Morus alba hybrid had more phenolic biosynthesis machinery than its cross-parent M. alba, whereas the Broussonetia papyrifera hybrid had significantly less phenolic machinery than B. papyrifera. This difference is probably the main reason for livestock preference for the hybrid of B. papyrifera over B. papyrifera in feed.