Chemical constituents from Melastoma dodecandrum and their inhibitory activity on interleukin-8 production in HT-29 cells

DIREN mitigates DSS-induced colitis in mice and attenuates collagen deposition via inhibiting the Wnt/β-catenin and focal adhesion pathways

BACKGROUND

DIREN is a SHE ethnic medicine with stasis-resolving, hemostasis, clearing heat, and removing toxin effects. It is clinically used in the treatment of gastrointestinal bleeding, such as ulcerative colitis (UC).

AIM OF THE STUDY

Fibrosis is one of the pathological changes in the progression of UC, which can make it challenging to respond to a treatment. We aimed to illuminate the role of DIREN in DSS-induced UC and tried to unveil its related mechanisms from two perspectives: intestinal inflammation and collagen deposition.

MATERIALS AND METHODS

A 2.5 % dextran sulfate sodium (DSS) water solution was used to induce colitis in mice. The therapeutic effect of DIREN was assessed using the disease activity index, histopathological score, and colon length. Masson and Sirius Red staining was used to observe the fibrosis in the colon. Apoptosis of colonic epithelial cells was observed by TUNEL immunofluorescence staining. RNA-seq observed differential genes and enrichment pathways. Immunohistochemistry and RT-qPCR were used to detect the expression of molecules related to fibrosis and focal adhesion signaling in colon tissue.

RESULTS

The administration of DIREN resulted in a reduction of disease activity index (DAI) in mice with UC while simultaneously promoting an increase in colon length. DIREN mitigated the loss of goblet cells in the colon of UC mice and maintained the integrity of the intestinal mucosa barrier. Masson staining revealed a reduction in colonic fibrosis with DIREN treatment, while Sirius red staining demonstrated a decrease in collagen Ⅰ deposition. DIREN reduced apoptosis of colonic epithelial cells and the expression of genes, such as CDH2, ITGA1, and TGF-β2. Additionally, the results of GSEA analysis of colon tissue transcriptome showed that the differentially expressed genes were enriched in the focal adhesion pathway. DIREN was found to downregulate the protein expression of BAX, N-cadherin, β-catenin, Integrin A1, and Vinculin while upregulating the protein expression of BCL2. Additionally, it led to the co-expression of N-cadherin and α-SMA.

CONCLUSION

DIREN exerts a protective effect against DSS-induced UC by ameliorating colonic fibrosis via regulation of focal adhesion and the WNT/β-catenin signaling pathway, thereby inhibiting fibroblast migration and reducing collagen secretion.

Transcriptomic and metabolomic characterization of antibacterial activity of Melastoma dodecandrum

Antibacterial resistance poses a significant global threat, necessitating the discovery of new therapeutic agents. Plants are a valuable source of secondary metabolites with demonstrated anticancer and antibacterial properties. In this study, we reveal that Melastoma dodecandrum exhibits both bacteriostatic and bactericidal effects against Pseudomonas aeruginosa and Staphylococcus aureus. Treatment with plant extracts results in membrane damage and a reduction in P.aeruginosa swimming and swarming motility. A comparative analysis of bacterial transcriptomes exposed to M.dodecandrum extracts and four distinct antibiotics indicates that the extracts may trigger similar transcriptomic responses as triclosan, a fatty acid synthesis inhibitor. Activity-guided fractionation suggests that the antibacterial activity is not attributable to hydrolyzable tannins, but to unidentified minor compounds. Additionally, we identified 104 specialized metabolic pathways and demonstrated a high level of transcriptional coordination between these biosynthetic pathways and phytohormones, highlighting potential regulatory mechanisms of antibacterial metabolites in M.dodecandrum.

Identification of a novel α-glucosidase inhibitor from Melastoma dodecandrum Lour. fruits and its effect on regulating postprandial blood glucose

Melastoma dodecandrum Lour. (MDL) extracts have shown potent α-glucosidase inhibitory activity, suggesting MDL might be a good source of α-glucosidase inhibitors. The aim of the study was to identify compounds in MDL extracts with α-glucosidase inhibitory activities and evaluate their effect on postprandial blood glucose as well as elucidating the underlying mechanisms of inhibition. A total of 34 polyphenols were identified in MDL fruits, among which 10 anthocyanins and three proanthocyanidin derivatives were discovered for the first time. Dosing mice with MDL extracts (100 mg/kg body weight, by gavage) was associated with a significantly decrease in postprandial blood glucose concentrations after oral administration of maltose. The most potent α-glucosidase inhibitor was identified as casuarictin (IC₅₀ of 0.21 μg/mL). Casuarictin bound competitively to α-glucosidase, occupying not only the catalytic site but also forming strong hydrogen bonds with α-glucosidase residues. Therefore, casuarictin derived from MDL fruits might be used as novel α-glucosidase inhibitor in functional foods or other dietary products.

Antiproliferative Activity of Buddleja saligna (Willd.) against Melanoma and In Vivo Modulation of Angiogenesis

Melanoma cells secrete pro-angiogenic factors, which stimulates growth, proliferation and metastasis, and therefore are key therapeutic targets. Buddleja saligna (BS), and an isolated triterpenoid mixture (DT-BS-01) showed a fifty percent inhibitory concentration (IC₅₀) of 33.80 ± 1.02 and 5.45 ± 0.19 µg/mL, respectively, against melanoma cells (UCT-MEL-1) with selectivity index (SI) values of 1.64 and 5.06 compared to keratinocytes (HaCat). Cyclooxygenase-2 (COX-2) inhibition was observed with IC₅₀ values of 35.06 ± 2.96 (BS) and 26.40 ± 4.19 µg/mL (DT-BS-01). BS (30 µg/mL) significantly inhibited interleukin (IL)-6 (83.26 ± 17.60%) and IL-8 (100 ± 0.2%) production, whereas DT-BS-01 (5 µg/mL) showed 51.07 ± 2.83 (IL-6) and 0 ± 6.7% (IL-8) inhibition. Significant vascular endothelial growth factor (VEGF) inhibition, by 15.84 ± 4.54 and 12.21 ± 3.48%, respectively, was observed. In the ex ovo chick embryo yolk sac membrane assay (YSM), BS (15 µg/egg) significantly reduced new blood vessel formation, with 53.34 ± 11.64% newly formed vessels. Silver and palladium BS nanoparticles displayed noteworthy SI values. This is the first report on the significant anti-angiogenic activity of BS and DT-BS-01 and should be considered for preclinical trials as there are currently no US Food and Drug Administration (FDA) approved drugs to inhibit angiogenesis in melanoma.

Structural Characterization and Assessment of Anti-Inflammatory Activities of Polyphenols and Depsidone Derivatives from Melastoma malabathricum subsp. normale

The roots of Melastoma malabathricum subsp. normale (D. Don) Karst. Mey have been used in traditional ethnic medicine systems in China to treat inflammation-triggered ailments, such as trauma, toothache, and fever. Therefore, the aim of this study is to screen for compounds with anti-inflammatory activity in the title plant. The extract of M. malabathricum subsp. normale roots was separated using various chromatographic methods, such as silica gel, ODS C18, MCI gel, and Sephadex LH-20 column chromatography, as well as semi-preparative HPLC. One new complex tannin, named whiskey tannin D (1), and an undescribed tetracyclic depsidone derivative, named guanxidone B (2), along with nine known polyphenols (2–10) and three known depsidone derivatives (12–14) were obtained from this plant. The structures of all compounds were elucidated by extensive NMR and CD experiments in conjunction with HR-ESI-MS data. All these compounds were isolated from this plant for the first time. Moreover, compounds 1–4, 8, and 10–14 were obtained for the first time from the genus Melastoma, and compounds 1, 2, and 11–14 have not been reported from the family Melastomataceae. This is the first report of complex tannin and depsidone derivatives from M. malabathricum subsp. normale, indicating their chemotaxonomic significance to this plant. Compounds 1–12 were investigated for their anti-inflammatory activities on the production of the nitric oxide (NO) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and compounds 1, 11, and 12 showed anti-inflammatory activities with IC₅₀ values of 6.46 ± 0.23 µM, 8.02 ± 0.35 µM, and 9.82 ± 0.43 µM, respectively. The structure–activity relationship showed that the catechin at glucose C-1 in ellagitannin was the key to its anti-inflammatory activity, while CH₃O- at C-16 of aromatic ring A in depsidone derivatives had little effect on its anti-inflammatory activity. The study of structure–activity relationships is helpful to quickly discover new anti-inflammatory drugs. The successful isolation and structure identification of these compounds, especially complex tannin 1, not only provide materials for the screening of anti-inflammatory compounds, but also provide a basis for the study of chemical taxonomy of the genus Melastoma.

Chemical composition, quality attributes and antioxidant activity of stirred-type yogurt enriched with Melastoma dodecandrum Lour fruit powder

Incorporation of Melastoma dodecandrum Lour fruit powder as a promising functional ingredient for stirred-type yogurt (STY) improved physicochemical properties, polyphenol contents, antioxidant activity, microstructure, and texture of STY.

In Vitro Selective Antibacterial and Antiproliferative Effects of Ethanolic Extracts from Cambodian and Philippine Plants Used in Folk Medicine for Diarrhea Treatment

Bacterial diarrhea remains a global health problem, especially in developing tropical countries. Moreover, dysbiosis caused by diarrheagenic bacteria and inappropriate antimicrobial treatment has been associated with intestinal carcinogenesis. Despite the rich tradition of the use of herbs for the treatment of gastrointestinal disorders in Cambodian and Philippine folk medicine, many of them have not yet been systematically studied for their in vitro selective inhibitory effects on intestinal bacteria and cells. In the present study, in vitro inhibitory activities of 35 ethanolic extracts derived from 32 Cambodian and Philippine medicinal plants were determined by broth microdilution method against 12 pathogenic bacteria. Furthermore, cytotoxicity against intestinal cancer cells (Caco-2 and HT-29) using thiazolyl blue tetrazolium bromide cytotoxicity assay and safety to six beneficial intestinal bacteria (bifidobacteria and lactobacilli) and intestinal normal cells (FHs 74 Int) were determined for the antimicrobially active extracts. Selectivity indices (SIs) were calculated among the averages of minimum inhibitory concentrations (MICs), half-maximal inhibitory concentrations (IC50), and 80% inhibitory concentrations of proliferation (IC80) for each type of the tested agents. The extracts of Artocarpus blancoi (Elmer) Merr. (Moraceae), Ancistrocladus tectorius (Lour.) Merr. (Ancistrocladaceae), and Pentacme siamensis (Miq.) Kurz (Dipterocarpaceae) produced significant growth-inhibitory effects (MICs = 32-512 μg/ml) against intestinal pathogenic bacteria at the concentrations nontoxic to normal intestinal cells (IC80 values >512 μg/ml; SIs = 0.11-0.2). Moreover, the extract of P. siamensis (Miq.) Kurz was relatively safe to beneficial bacteria (MICs ≥512 μg/ml; SI = 0.1), and together with A. blancoi (Elmer) Merr., they selectively inhibited intestinal cancer cells (IC50 values ≥51.98 ± 19.79 μg/ml; SIs = 0.3 and 0.6). Finally, a strong selective antiproliferative effect on cancer cells (IC50 values 37.89 ± 2.68 to 130.89 ± 13.99 μg/ml; SIs = 0.5) was exerted by Ehretia microphylla Lam. (Boraginaceae), Lagerstroemia cochinchinensis Pierre ex Gagnep. (Lythraceae), and Melastoma saigonense (Kuntze) Merr. (Melastomataceae) (leaves with flower buds). The results suggest that the above-mentioned species are promising materials for the development of new selective antibacterial and antiproliferative agents for the treatment of infectious diarrhea and associated intestinal cancer diseases. However, further research is needed regarding the isolation and identification of their active constituents.

A review of the traditional uses, phytochemistry and biological activities of the Melastoma genus

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Melastoma consists of approximately 100 species distributed widely in tropical and subtropical countries, and Melastoma species are often used for medicinal purposes, such as treatment for bleeding, diarrhea, diabetes, and gynecological tumors by local people, mostly in Southeast Asian countries.

AIM OF THE REVIEW

The present review summarizes the traditional uses, phytochemistry and pharmacology of species belonging to Melastoma to suggest further research strategies and to facilitate the exploitation of the therapeutic potential of Melastoma species for the treatment of human disorders.

MATERIALS AND METHODS

Information related to the traditional uses, phytochemistry and pharmacological activities was systematically collected by searching for the word "Melastoma" in electronic databases, including SciFinder, Web of Science, PubMed, and Google Scholar, from Apr. 1968 until Dec. 2019.

RESULTS

A systematic literature survey revealed that Melastoma spp. are widely distributed in southern Asia to northern Oceania and the Pacific Islands and are traditionally used to treat bleeding, diarrhea, swelling, and gynecological tumors. Approximately 142 compounds, including flavonoids, tannins, phenylpropanoids, organic acids, terpenoids, and steroids, have been reported from Melastoma spp. Different extracts have been evaluated for their pharmacological activities, including anti-inflammatory, hemostatic, anticoagulant, cytotoxic, antibacterial, antioxidant, hepatoprotective, gastroprotective and hypoglycemic activities.

CONCLUSIONS

Melastoma spp. are popularly used in Southeast Asian countries as effective herbs and are rich in flavonoids, tannins and organic acids with valuable medicinal properties. However, additional studies of the chemical constituents and the mechanism-based pharmacological activities of many members of Melastoma are still needed for developing new plant-derived drugs. In addition, studies on the clinical safety and efficacy of Melastoma are also needed.

Safety Assessment of Methanol Extract of Melastoma malabathricum L. Leaves following the Subacute and Subchronic Oral Consumptions in Rats and Its Cytotoxic Effect against the HT29 Cancer Cell Line

Methanol extract of Melastoma malabathricum (MEMM) has been traditionally used by the Malay to treat various ailments. In an attempt to develop the plant as an herbal product, MEMM was subjected to the subacute and subchronic toxicity and cytotoxicity studies. On the one hand, the subacute study was performed on three groups of male and three groups of female rats (n = 6), which were orally administered with 8% Tween 80 (vehicle control group) or MEMM (500 and 1000 mg/kg) daily for 28 days, respectively. On the other hand, the subchronic study was performed on four groups of rats (n = 6), which were orally administered with 8% Tween 80 (vehicle control group) or MEMM (50, 250, and 500 mg/kg) daily for 90 days, respectively. In the in vitro study, the cytotoxic effect of MEMM against the HT29 colon cancer cell line was assessed using the MTT assay. MEMM was also subjected to the UHPLC-ESI-HRMS analysis. The results demonstrated that MEMM administration did not cause any mortality, irregularity of behaviour, modification in body weight, as well as food and water intake following the subacute and subchronic oral treatment. There were no significant differences observed in haematological parameters between treatment and control groups in both studies, respectively. The in vitro study demonstrated that MEMM exerts a cytotoxic effect against the HT29 colon cancer cell line when observed under the inverted and phase-contrast microscope and confirmed by the acridine orange/propidium iodide (AOPI) staining. The UHPLC-ESI-HRMS analysis of MEMM demonstrated the occurrence of several compounds including quercetin, p-coumaric acid, procyanidin A, and epigallocatechin. In conclusion, M. malabathricum leaves are safe for oral consumption either at the subacute or subchronic levels and possess cytotoxic action against the HT29 colon cancer cells possibly due to the synergistic action of several flavonoid-based compounds.

Extraction, Enrichment, and Quantification of Main Antioxidant Aglycones of Flavonoids and Tannins from Melastoma Dodecandrum Lour.: Guided by UPLC-ESI-MS/MS

The objective of this work was to determine the main antioxidant aglycones of flavonoids and tannins in antioxidant extracts from Melastoma dodecandrum Lour. (MD), based on its extraction and purification process optimization and component identification by UPLC-ESI-MS/MS. Firstly, the ultrasound-assisted extraction (UAE) process for antioxidants was established by using single factor tests and response surface optimization. Evaluating by DPPH radical scavenging assay, the antioxidant capacity of MD could reach 2742.27 ± 93.86 (μmol Trolox/g) under the optimized conditions including methanol concentration (61%, v/v), extraction time (45 min), liquid-solid ratio (0.46 ml/mg), and extraction temperature (25°C). Then, the antioxidants in the solution were enriched by using macroporous resins. Because of the highest adsorption capacity and desorption ratio, HPD 500 was selected out of 14 macroporous resins for further study based on the static adsorption and desorption tests. The adsorption mechanism of the HPD 500 resin presented that pseudo-first-order kinetics model and Freundlich isotherm model could adequately explain the adsorption process. After the antioxidants were dynamically saturated by HPD 500, the column was eluted with different concentrations of ethanol (0, 25, 50, 75, and 100%, v/v). Among the above five ethanol fractions, 50% ethanol fraction showed the strongest antioxidant activity and more than 95% antioxidants adsorbed in HPD500 could be eluted by 75% ethanol. Guided by analysis results of UPLC-ESI-MS/MS, main antioxidant aglycones of flavonoids and tannins in each ethanol elution fraction were quantitatively detected. Finally, according to the correlation analysis between the antioxidant capacity of each ethanol elution fraction and its content of 10 main flavonoids and phenolic acids, the antioxidant activities of MD could mainly contribute to tannins containing phenolic units such as ellagic acid and/or gallic acid. The results of this work would provide useful information for the production of antioxidants from MD. Thus, the analysis methods could also be a quality control tool for material or products related with MD.

Structure and features of the complete chloroplast genome of Melastoma dodecandrum

Melastoma dodecandrum, the only creeping species in the Melastoma genus, serves as a medicinal herb in southeast China. It belongs to the huge family Melastomataceae, which contains over 5000 species worldwide. In this study, we used next-generation sequencing to determine the complete chloroplast genome sequences of M. dodecandrum, which is a circular molecule of 156,611 bp in length. After annotation, we identified 131 putative genes in total, comprised of 85 protein-coding genes, 38 transfer RNA genes and 8 ribosomal RNA genes. Genome structure, GC content, repeat sequences and codon usage were investigated to gain a comprehensive understanding of this genome. Furthermore, we conducted comparative genome analyses between the M. dodecandrum genome and that of four other Melastomataceae species. Additionally, a phylogenetic analysis was performed based on available chloroplast genomes of Melastomataceae species and several Myrtaceae species, revealing the taxonomic relationships between M. dodecandrum and related species. In conclusion, our study represents the first look into the complete chloroplast genome of M. dodecandrum, providing abundant information for further studies such as species identification, taxonomy and phylogenetic resolution of Melastomataceae species.

Pharmacological Review on Asiatic Acid and Its Derivatives: A Potential Compound

Natural triterpenes represent a group of pharmacologically active and structurally diverse organic compounds. The focus on these phytochemicals has been enormous in the past few years, worldwide. Asiatic acid (AA), a naturally occurring pentacyclic triterpenoid, is found mainly in the traditional medicinal herb Centella asiatica. Triterpenoid saponins, which are the primary constituents of C. asiatica, are commonly believed to be responsible for their extensive therapeutic actions. Published research work has described the molecular mechanisms underlying the various biological activities of AA and its derivatives, which vary for each chronic disease. However, a compilation of the various pharmacological properties of AA has not yet been done. Herein, we describe in detail the pharmacological properties of AA and its derivatives that inhibit multiple pathways of intracellular signaling molecules and transcription factors that are involved in the various stages of chronic diseases. Furthermore, the pharmacological activities of AA were compared with two natural compounds: curcumin and resveratrol. This review summarizes the research on AA and its derivatives and helps to provide future directions in the area of drug development.

Anti-inflammatory properties of an extract of M. ilicifolia in the human intestinal epithelial Caco-2 cell line

ETHNOPHARMACOLOGY RELEVANCE

Maytenus ilicifolia is a Celastracea plant used in traditional medicine to alleviate digestive tract inflammatory disorders.

AIM OF THE STUDY

We investigated anti-inflammatory properties of M. ilicifolia crude extract towards Caco-2 cell line, as a model of Toll-like Receptor 2 (TLR-2) inflammatory pathway.

MATERIALS AND METHODS

Toxicity was assessed following culture of Caco-2 with M. ilicifolia, using apparent cell permeability and trans-epithelial electric resistance. Anti-inflammatory properties of M. ilicifolia were assessed through IL-8 secretion and TLR-2 associated gene expression of Caco-2 cells with or without an LTA challenge.

RESULTS

M. ilicifolia was not toxic to Caco-2 cells. M. ilicifolia down-regulated TLR2 expression with and without LTA challenge but had no effect on other genes. Following LTA challenge of Caco-2 cells, 100 and 200µg/mL M. ilicifolia abrogated IL-8 secretion.

CONCLUSIONS

We provide preliminary data for some M. ilicifolia anti-inflammatory properties. Further research must establish the full extent and mode of action on particular inflammatory pathways.