Embelin: A novel XIAP inhibitor for the prevention and treatment of chronic diseases.

Chronic diseases are a serious health concern worldwide, especially in the elderly population. Most chronic diseases like cancer, cardiovascular ailments, neurodegenerative disorders, and autoimmune diseases are caused due to the abnormal functioning of multiple signaling pathways that give rise to critical anomalies in the body. Although a lot of advanced therapies are available, these have failed to entirely cure the disease due to their less efficacy. Apart from this, they have been shown to manifest disturbing side effects which hamper the patient's quality of life to the extreme. Since the last few decades, extensive studies have been done on natural herbs due to their excellent medicinal benefits. Components present in natural herbs target multiple signaling pathways involved in diseases and therefore hold high potential in the prevention and treatment of various chronic diseases. Embelin, a benzoquinone, is one such agent isolated from Embelia ribes, which has shown excellent biological activities toward several chronic ailments by upregulating a number of antioxidant enzymes (e.g., SOD, CAT, GSH, etc.), inhibiting anti-apoptotic genes (e.g., TRAIL, XIAP, survivin, etc.), modulating transcription factors (e.g., NF-κB, STAT3, etc.) blocking inflammatory biomarkers (e.g., NO, IL-1ß, IL-6, TNF-α, etc.), monitoring cell cycle synchronizing genes (e.g., p53, cyclins, CDKs, etc.), and so forth. Several preclinical studies have confirmed its excellent therapeutic activities against malicious diseases like cancer, obesity, heart diseases, Alzheimer's, and so forth. This review presents an overview of embelin, its therapeutic prospective, and the molecular targets in different chronic diseases.

Embelia Laeta aqueous extract suppresses acute inflammation via decreasing COX-2/iNOS expression and inhibiting NF-κB pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: The root of Embelia laeta (L.) Mez., which is called Suanjifeng in Chinese ethnic Yao medicine, is traditionally for inflammation-related diseases, such as oral ulcer, sore throat, enteritis, and rheumatoid arthritis. However, the biological properties and the underlying mechanisms of Embelia laeta still need further studies. AIM OF THIS STUDY: The present study aims to investigate the anti-inflammatory effect and its underlying mechanisms of Embelia laeta. MATERIALS AND METHODS: In this study, except acute toxicity experiments, Kunming (KM) mice of either sex were enrolled to establish inflammatory model induced by xylene, acetic acid and carrageenan, respectively. Mice were randomly divided into different groups and pretreated by oral gavage with different doses of Embelia laeta aqueous extract (ELAE) (2.5, 5, 10 g/kg) and 10 mg/kg of Indo for 7 days. Ear edema, vascular permeability, abdominal writhing, and paw edema degree were detected in related experiments. Moreover, in the carrageenan-induced paw edema mice model, histological changes were detected by H&E staining. MDA, MPO and NO were detected by assay kit. Proinflammatory cytokines of IFN-γ, TNF-α, IL-1ß, IL-6 and PGE2 were detected by ELISA. Additionally, COX-2, iNOS and NF-κB pathway-related proteins were detected by Western blotting. RESULTS: Results showed that the ELAE evoked an obvious dose-dependent inhibition of ear edema induced by xylene, paw edema induced by carrageenan, as well as suppressing the increase of vascular permeability and writhing times elicited by acetic acid. Histopathological analysis indicated that ELAE could significantly decrease the cellular infiltration in paw tissue. ELAE showed antioxidant property through markedly decrease the MDA level and MPO activity in edema paw. In addition, ELAE decreased the proinflammatory cytokines IFN-γ, TNF-α, IL-1ß, IL-6, PGE2 and NO that induced by carrageenan. Western blotting results also showed that ELAE could obviously downregulate the COX-2 and iNOS expression. Further analysis revealed that ELAE also inhibited NF-κB from the cytoplasm to the nucleus and stabilize the conversion of IκBα. CONCLUSION: ELAE had powerful anti-inflammatory property, which might be had a close relationship with mediating proinflammatory cytokines production, decreasing the COX-2 and iNOS expression, and inhibiting the activation of NF-κB signaling pathway.

Metabolite profiling and evaluation of CYP450 interaction potential of 'Trimada'- an Ayurvedic formulation.

ETHNOPHARMACOLOGICAL RELEVANCE: Trimada is well-known polyherbal Ayurvedic formulation used in Indian Traditional medicine since ancient times. It consisted of three inebriant herbs including "Chitraka" (Plumbago zeylanica Linn. Family- Plumabaginaceae), "Musta" (Cyperus rotundus Linn. Family- Cyperaceae) and Vidanga (Embelia ribes Burm. F. Family- Myrsinaceae) in equal ratios as mentioned in Ayurveda. Trimada is traditionally used to increase the functioning of the digestive system and metabolism. Along with these, it also assists in the reduction of cholesterol as well as reduces stomach aches and chest pain. AIM OF THE STUDY: This study is aimed to identify the metabolites present in this polyherbal formulation. Further, the cytotoxicity and interaction potential of the formulation and individual herbs with Cytochrome P450 isozymes (CYP3A4, 2D6, 2C9, 1A2) was evaluated by MTT assay and CYP450 enzyme inhibition. The concentration of heavy metals was also determined. MATERIAL AND METHODS: Ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-QTOF-MS) analysis was performed to detect and identify the phytoconstituents in the formulation. Cytotoxicity of the formulation was evaluated by MTT assay. CYP450 enzyme interaction potential of the individual herbs and the Trimada formulation was carried out through CYP-CO assay and fluorometric high throughput screening (HTS) assay for individual isozymes. The content of heavy metal in the formulation was quantified by Atomic Absorption Spectroscopy. RESULTS: Trimada formulation exhibited lower cytotoxicity to human liver carcinoma cell line (HepG2). CYP-CO assay revealed that the interaction potential of individual herbs and Trimada on the liver microsomes was found to be lesser than the standard inhibitor ketoconazole. Individual herbs and Trimada formulation displayed higher IC50 values than the respective standard inhibitors in the fluorimetric assay. UPLC-QTOF-MS analysis showed the presence of a number of active phytoconstituents including sesquiterpenes, phenolic acids, benzoquinones, triterpenes and flavonoids. The heavy metal concentration in the traditional medicinal herbal formulation was found within the approved limit. CONCLUSIONS: This study suggested that the individual herbs and Trimada formulation exhibited low cytotoxicity and contributes insignificant interaction with CYP450 isozymes. So, the formulation is considered to be safe for its therapeutic management without any potential drug interaction involving CYP 450 isozymes.

Design, synthesis and α-glucosidase inhibition study of novel embelin derivatives.

Embelin is a naturally occurring para-benzoquinone isolated from Embelia ribes (Burm. f.) of the Myrsinaceae family. It was first discovered to have potent inhibitory activity (IC50 = 4.2 µM) against α-glucosidase in this study. Then, four series of novel embelin derivatives were designed, prepared and evaluated in α-glucosidase inhibition assays. The results show that most of the embelin derivatives synthesised are effective α-glucosidase inhibitors, with IC50 values at the micromolar level, especially 10d, 12d, and 15d, the IC50 values of which are 1.8, 3.3, and 3.6 µM, respectively. Structure-activity relationship (SAR) studies suggest that hydroxyl groups in the 2/5-position of para-benzoquinone are very important, and long-chain substituents in the 3-position are highly preferred. Moreover, the inhibition mechanism and kinetics studies reveal that all of 10d, 12d, 15d, and embelin are reversible and mixed-type inhibitors. Furthermore, docking experiments were carried out to study the interactions between 10d and 15d with α-glucosidase.

Chemical Profiling of Embelia ribes by Ultra-High-Performance Liquid Chromatography Quadrupole Time-of-Flight Tandem Mass Spectrometry and Its Antioxidant and Anti-inflammatory Activities In Vitro.

Embelia ribes is a traditional Chinese medicine compound used as a remedy for various diseases. Nevertheless, detailed information regarding its chemical composition is unavailable. Herein, ultra-high-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry was used to characterize the components of E. ribes. A total of 56 compounds, including 16 phenolics, 16 flavonoids, 4 coumarins, 5 fatty acids and 15 other compounds were identified. Furthermore, the total phenolic and total flavonoid content was also assessed; the acetic ether extract of E. ribes was an ideal source of phenolics (308.16 ± 0.00 mg gallic acid equivalents/g of extract) and flavonoids (62.00 ± 0.01 mg rutin equivalents/g of extract). Additionally, acetic ether extract exhibited a high antioxidation effect (ferric reducing activity power: 0.15 ± 0.01 mg/mL; 1,1-diphenyl-2-picrylhydrazyl: 0.18 ± 0.01 mg/mL; 2,2-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid: 0.06 ± 0.01 mg/mL). Further, the nitric oxide concentration in lipopolysaccharide-simulated macrophage RAW 264.7 cells and the pro-inflammatory cytokines (TNF-α and IL-6) were suppressed by acetic ether extract. These findings support the notion that E. ribes is an ideal antioxidant and anti-inflammatory agent.

Identification of embelin, a 3-undecyl-1,4-benzoquinone from Embelia ribes as a multitargeted anti-Alzheimer agent.

Beta-secreatse (BACE-1) and cholinesterases are clinically validated targets of Alzheimer's disease (AD), for which natural products have provided immense contribution. The multifaceted nature of AD signifies the need of multitargeted agents to tackle this disease. In the search of new natural products as dual BACE-1/cholinesterase inhibitors, a library of pure natural products was screened for inhibition of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and BACE-1. The screening efforts have identified 1,4-benzoquinone "embelin," a natural product derived from Embelia ribes displaying inhibition of all three enzymes, with IC50 values of 2.5, 5.4, and 2.1 µM, respectively. This screen has also identified isoquinoline alkaloids papaverine and L-tetrahydropalmatine as AChE inhibitors. Kinetic study has shown that embelin inhibits EeAChE and EqBChE with ki values of 4.59 and 0.57 µM, in an uncompetitive and noncompetitive manner, respectively. The interactions of embelin with allosteric peripheral anionic site of cholinesterases, has further supported the results of kinetic study. Embelin has also enhanced the activity of P-gp in LS-180 cells, the efflux pump which is involved in the clearance of amyloid-ß from AD brain. Further, the cell viability study in neuronal cell line has indicated the excellent therapeutic window of embelin. These results are indicative of the fact that embelin is a multitargeted agent playing role in stopping the formation of amyloid-ß oligomers (via inhibition of BACE-1), improves cholinergic-transmission (via inhibition of AChE/BChE) and increases amyloid-ß clearance (via P-gp induction).

A new alkylbenzoquinone from Embelia rowlandii Gilg. (Myrsinaceae).

A new alkylbenzoquinone named embeliquinone (1) together with five known compounds, lupeol (2), 3-O-[6'-O-palmitoyl-ß-d-glucosyl]-spinasta-7,22(23)-diene (3), quercetin (4), (2S,3S,4R,8E)-2-[(2'R)-2'-hydroxy-heneicosanoylamino]-heneicosane-1,3,4-triol-8-ene (5), and ß-sitosterol-3-O-ß-d-glucopyranoside (6) were isolated from the MeOH leaf extract of Embelia rowlandii by using repeated open column chromatography techniques. The structure of the new compound was characterized by analyses of 1D- and 2D-NMR, and MS data. Embeliquinone (1) had moderate anti-cell proliferation activity against A549 cell line with the IC50 value of 21.8 µM. In addition, 1 exhibited weak antibacterial activities against Klebsiella pneumoniae and Staphylococcus aureus with an MIC value of 206.0 µM in both cases.

X-linked inhibitor of apoptosis protein inhibitor Embelin induces apoptosis via PI3K/Akt pathway and inhibits invasion in osteosarcoma cells.

BACKGROUND: Embelin is an active compound identified as a novel X-linked inhibitor of apoptosis protein (XIAP) inhibitor from the Embelia ribes that exhibits various medicinal effects including anti-inflammatory and anticancer activities. However, the therapeutic effect of Embelin to human osteosarcoma is not yet determined. OBJECTIVES: In this study, we evaluated the sensitizing potential of Embelin on promoting apoptosis to cause osteosarcoma cell death and inhibiting its invasion. METHODS: We uesd 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide to detect the survival rates of osteosarcoma cells, Western blot to detect the expression of proteins in U-2 OS and MG63 cells, and fluorescence microscope to observe the morphology of apoptotic cells. RESULTS: The survival of osteosarcoma cells decreased, When Embelin was used. Obvious condensed and flared fluorescence was observed, when used high-dose Embelin. There was an increase of caspase-3, cleaved caspase-3, caspase-8, and caspase-9 in Embelin group, while PI3K, AKt, p-AKt, X-linked inhibitor of apoptosis protein, and MMP-9 were downregulated. The invasion of Embelin application was significantly lower than that of the control application. CONCLUSION: Embelin promoted apoptosis via XIAP and PI3K/Akt signaling pathway. XIAP inhibitor Embelin inducing apoptosis could cause osteosarcoma cell death and inhibit its invasion.

New alkylresorcinols from the fruits of Embelia ribes.

Nine new alkylresorcinols, designated as embelialkylresorcinols A-I (1-9), along with five known compounds (10-14) were isolated from the fruits of Embelia ribes. Their structures were elucidated by extensive spectroscopic analysis (1D, 2D NMR and HRESIMS), optical rotation data and modified Mosher method. Notably, embelialkylresorcinols A-H (1-8), possessing double aromatic rings linked with an aliphatic chain, are reported from the genus of Embelia (Myrsinaceae) for the first time. Most of the isolated compounds were evaluated for cytotoxic activity, and the results indicated that compounds 3, 5, 6 and 8 displayed moderate cytotoxicity against three human cancer cell lines (Hep3B, A549 and HCC1806) with IC50 values ranging from 23.06 to 41.49 µM.

Antiviral activity of Embelia ribes Burm. f. against influenza virus in vitro.

Viral respiratory infections are raising serious concern globally. Asian medicinal plants could be useful in improving the current treatment strategies for influenza. The present study examines the activity of five plants from Bangladesh against influenza virus. MDCK cells infected with influenza virus A/Puerto Rico/8/34 (H1N1) were treated with increasing concentrations of ethyl acetate extracts, and their cytotoxicity (CC50), virus-inhibiting activity (IC50), and selectivity index (SI) were calculated. The ethyl acetate extract of fruits of Embelia ribes Burm. f. (Myrsinaceae) had the highest antiviral activity, with an IC50 of 0.2 µg/mL and a SI of 32. Its major constituent, embelin, was further isolated and tested against the same virus. Embelin demonstrated antiviral activity, with an IC50 of 0.3 µM and an SI of 10. Time-of-addition experiments revealed that embelin was most effective when added at early stages of the viral life cycle (0-1 h postinfection). Embelin was further evaluated against a panel of influenza viruses including influenza A and B viruses that were susceptible or resistant to rimantadine and oseltamivir. Among the viruses tested, avian influenza virus A/mallard/Pennsylvania/10218/84 (H5N2) was the most susceptible to embelin (SI = 31), while A/Aichi/2/68 (H3N2) virus was the most resistant (SI = 5). In silico molecular docking showed that the binding site for embelin is located in the receptor-binding domain of the viral hemagglutinin. The results of this study provide evidence that E. ribes can be used for development of a novel alternative anti-influenza plant-based agent.

Embelin: a benzoquinone possesses therapeutic potential for the treatment of human cancer.

Natural products have been gaining recognition and are becoming a significant part of research in the area of drug development and discovery. Phytochemicals derived from these sources have been comprehensively studied and have displayed a wide range of activities against many fatal diseases including cancer. One such product that has gained recognition from its pharmacological properties and nontoxic nature is embelin, obtained from Embelia ribes. Amid all the vivid pharmacological activities, embelin has gained its prominence in the area of cancer research. Embelin binds to the BIR3 domain of XIAP, preventing the association of XIAP and caspase-9 resulting in the suppression of cell growth, proliferation and migration of various types of cancer cells. Furthermore, embelin modulates anti-apoptotic pathways by suppressing the activity of NF-κB, PI3-kinase/AKT, JAK/STAT pathway - among others. The present review summarizes the various reported effects of embelin on different types of cancer cells and highlights the cellular mechanisms of action.

Evaluation of selected Indian medicinal plants for antagonistic potential against Malassezia spp. and the synergistic effect of embelin in combination with ketoconazole.

The genus Malassezia comprises of extremely lipophilic yeasts secreting lipases as a vital factor for survival. They are emerging as opportunistic pathogens in medical microbiology and dermatology by causing recurring and recalcitrant infection. Combinatorial therapy is a constructive way to combat infectious diseases. In that prospect, totally 16 Indian medicinal plants were screened, among which a maximum degree of antimicrobial activity was ascertained in Embelia ribes. Subsequently embelin was identified as the bioactive principle with antagonistic potential by comparative antimicrobial assay and FTIR analysis. The MIC of embelin was determined as 400 µg/ml exhibiting ∼75% of growth inhibition. Further, a fungistatic activity based on anti-lipase potential (65-89%) of embelin has been clearly substantiated by XTT and lipase assay. In addition, embelin exhibited a synergistic effect with the antifungal drug ketoconazole (KTZ) against four different Malassezia spp. with FIC index of 0.5. Therefore, the combinations of embelin and KTZ may represent a promising therapeutic regimen to treat Malassezia infections with subjugated clinical and environmental toxicity. To the best of our knowledge, this is the first report delineating the anti-lipase activity of embelin and in vitro synergistic interaction between embelin and KTZ against Malassezia spp.

Single-step isolation of embelin using high-performance countercurrent chromatography and determination of the fatty acid composition of seeds of Embelia schimperi.

Embelin (2,5-dihydroxy-3-undecyl-p-benzoquinone) is known for its potent anthelmintic activity, but also for wound-healing, antidiabetic, anticonvulsant, antitumour, anti-inflammatory, analgesic, hepatoprotective, antioxidant, antibacterial and antispermatogenic activities. A high-performance countercurrent chromatography method was developed for the purification of embelin from an extract of the seeds of Embelia schimperi fruit. The optimized solvent system (n-hexane-ethylacetate-ethanol-water, 7:3:7:3) resulted in the isolation of 13.9 mg of embelin, directly from 100 mg of crude extract, in a single step within a short time (40 min). Although the compound appeared to be completely pure when analysed by ultra-performance liquid chromatography (UPLC) with photo diode array detection, the purity was established as ~90% by UPLC-mass spectrometry. Furthermore, we report the fatty acid composition of the seeds of E. schimperi fruit. Nine fatty acids were quantified from the fruit seed extract by gas chromatography-mass spectrometry, with linoleic (46.4%), palmitic (21.5%) and oleic (19.6%) acids making up the largest proportions.

Antipsychotic activity of embelin isolated from Embelia ribes: A preliminary study.

BACKGROUND: Embelia ribes is claimed in Indian traditional medical practice to be useful in the treatment of nervous diseases. Embelin, an alkyl substituted hydroxy benzoquinone, is a major active constituent of E. ribes. The present preliminary study was intended to evaluate antipsychotic activity of embelin against apomorphine-induced climbing behaviour in mice and stereotyped behaviour in rats. METHODS: Two doses of embelin (5 and 10mg/kg) were administered once daily for 15days before exposure to apomorphine. On the concluding day of pre-treatment, after apomorphine-injection, the rodents were assessed for climbing and stereotyped behaviours according to the published scoring system. Thereafter, neurotransmitters (dopamine, noradrenaline and serotonin) levels were estimated in rodent brains. RESULTS: Embelin pre-treatment significantly inhibited apomorphine-induced climbing and stereotyped behaviours in mice and rats, respectively. Further, embelin also statistically reversed elevated levels of dopamine, noradrenaline and serotonin neurotransmitters in the brain of mice and rats. Embelin showed more significant results at high dose (10mg/kg) than low dose (5mg/kg) in both the tested models. CONCLUSION: Considering the present pharmacological profile of embelin, it is suggested that embelin possesses antipsychotic activity in the treatment of psychotic disorders. However, further research is warranted for evaluating its exact mechanism of action.

ROS-mediated induction of apoptosis by benzoquinone embelin in human colon adenocarcinoma cells HT-29.

Background Embelin is a benzoquinone reported to possess anticancer activity in several in vivo and in vitro models of carcinogenesis, especially hematopoietic and prostate malignancy. A detailed investigation on the influence of embelin on epithelial malignancy model system, especially colon adenocarcinoma, is lacking. The objective of the current study is to investigate the antiproliferative, antiinvasive and proapoptotic potential of embelin on colon adenocarcinoma cell line HT-29. Methods The effect of embelin (35 µg/mL for 24 h) on cell proliferation was assessed by Sulforhodamine B assay and bromodeoxyuridine incorporation test, antiinvasive effect by Boyden chamber assay and scratch assay. Proapoptotic effects of embelin were determined by studies on DNA fragmentation, annexin V-FITC labeling, TUNEL assay, COMET assay and assay of caspase-3 activity. Influence of embelin on the expression of genes regulating apoptosis (caspase 3 and 9, Bcl-2, Bax, cytochrome C and X-linked inhibitor of apoptosis protein) and migration/invasion (matrix metalloproteinase [MMP]-2 and MMP-9) was investigated by reverse transcription polymerase chain reaction (PCR). Further, the effect of embelin on the levels of reactive oxygen species (ROS), lipid peroxides, nitric oxide, mitochondrial membrane potential and antioxidant status (total reduced glutathione [GSH] and GSH-S-transferase) was evaluated. Results Results implicated that embelin treatment inhibited proliferation (IC50 35 µg/mL), induced DNA fragmentation, phosphatidyl serine externalization, increased caspase expression, decreased cell migration and expression of MMPs in HT-29 cells. Interestingly, embelin exhibited prooxidant effect on HT-29 cells and induced excessive ROS generation resulting in apoptotic cell death. Conclusions To conclude, embelin treatment could be a promising strategy for the chemotherapy of colon cancer.

Chemical and Biological Aspects of the Natural 1,4-Benzoquinone Embelin and its (semi-)Synthetic Derivatives.

BACKGROUND: Like the impressive biological properties of embelin, its chemical aspects have raised the interest of scientists in the field as well. A detailed understanding of the chemistry of embelin is necessary to fully exploit it medicinally. METHODS: Search for embelin isolation and its chemical modifications was carried out using web-based literature searching tools such as Pubmed and Scifinder. Pertinent literature is covered up to 2016. Structures of bioactive embelin derivatives are provided. RESULTS: Pure embelin, obtained from Embelia ribes berries extraction or by total synthesis, was applied for a number of biological assays. Semi-synthetic and total synthetic approaches led to new high affinity embelin-derived inhibitors of crucial protein targets and to new embelin derivatives with improved pharmacological properties (e.g., with better water-solubility or as applications for drug carrier systems). CONCLUSION: This review provides a summary of the rich chemistry of embelin and the latest developments in the field of optimized (semi-)synthetic embelin derivatives including their biological activities.

Evaluation of anthelmintic potential of the Ethiopian medicinal plant Embelia schimperi Vatke in vivo and in vitro against some intestinal parasites.

BACKGROUND: Embelia schimperi has been used for the treatment of intestinal parasites especially tapeworm infestations for centuries in Ethiopia. However, there is lack of scientific based evidences regarding the efficacy, safety and phytochemical analysis of this plant despite its frequent use as an anthelmintic. This study has therefore evaluated the efficacy and acute toxicity of E. schimperi thereby generating relevant preclinical information. METHODS: The anthelmintic activities of the crude hydroalcoholic extract of E. schimperi and the isolated compound, embelin, were conducted using in vivo and in vitro models against the dwarf tapeworm, Hymenolepis nana, and the hookworm, Necator americanus, respectively. LD50 of the crude hydroalcoholic extract was determined using Swiss albino mice following the OECD guidelines. Chemical characterization of the isolated embelin was conducted using UV-spectroscopy, HPLC and NMR. RESULTS: In the acute toxicity study no prominent signs of toxicity and mortality were recorded among the experimental animals at the highest administered dose. Hence the LD50 of the plant was found to be higher than 5000 mg/kg. In vivo cestocidal activity of the crude hydroalcoholic extract of E. schimperi showed 100% parasite clearance at 1000 mg/kg, while the diammonium salt of embelin showed 85.3% parasite clearance at 750 mg/kg. The in vitro anthelminthic activity study revealed that the LC50 value of the crude extract and albendazole were 228.7 and 51.33 µg/mL, respectively. CONCLUSION: The results clearly indicated that the hydroalcoholic extract of E. schimperi and the diammonium salt of the isolated compound embelin had anthelmintic activity against hookworm larva in vitro and H. nana in vivo. Hence the findings of this study showed Embelia schimperi appears to possess some anthelmintic activity that may support the usage of these plants by local traditional healers to treat helminthic infestations.

α-Glucosidase inhibitors from the leaves of Embelia ribes.

A novel and rare 1,4-dehydrated ceramide, embelamide (1), and a new C-glycoalkaloid which is based on a ß-carboline ring system, 1-(2'-deoxy-α-d-ribopyranosyl)-ß-carboline (4), were isolated from the CHCl3 soluble fraction of the leaves of Embelia ribes (Myrsinaceae), together with thirteen known compounds (2-3, 5-15). Their structures were elucidated on the basis of spectroscopic data. Compounds 1, and 5-12 possessed significant α-glucosidase inhibitory activity in a concentration-dependent manner, and showed more potent inhibitory activity, with IC50 values ranging from 1.3 to 155.0 µM, than that of a positive control acarbose (IC50, 214.5 µM).

Synthesis and anti-proliferative activities of new derivatives of embelin.

Embelin (1), a benzoquinone isolated from Embelia ribes is known to possess variety of biological activities. Despite of several promising biological activities, preclinical efforts on embelin were hampered because of its poor aqueous solubility. In order to address the solubility issue, herein, we have synthesized a series of Mannich products of embelin by treating it with various secondary amines. The synthesized compounds were screened for antiproliferative and antimicrobial activities. In cytotoxicity screening, the benzyl-piperidine linked derivative 8m was found to possess better antiproliferative activity compared to parent natural product embelin against a panel of cell lines including HCT-116, MCF-7, MIAPaCa-2 and PC-3 with IC50 values of 30, 41, 34 and 36 µM, respectively. The mechanistic study of compound 8m revealed that it exhibits cytotoxicity via induction of apoptosis and mitochondrial membrane potential loss. Further, the compounds were tested for antimicrobial activity where dimethylamino- 8a and piperidine linked derivative 8b displayed antibacterial activity against Staphylococcus aureus with MIC values of 8 and 16 µg/mL, respectively. Mannich derivatives did now show improved aqueous solubility, however their hydrochloride salts 8a·HCl, 8b·HCl and 8m·HCl showed significantly improved aqueous solubility without affecting biological activities of parent Mannich derivatives.

Embelin (2,5-dihydroxy-3-undecyl-p-benzoquinone): a bioactive molecule isolated from Embelia ribes as an effective photodynamic therapeutic candidate against tumor in vivo.

The present study was carried out to assess the photosensitizing potential of embelin, the biologically active natural product isolated from Embelia ribes in photodynamic therapy (PDT) experiments in vivo. In vitro PDT clearly indicated that embelin recorded significant cytotoxicity in Ehrlich's Ascites Carcinoma (EAC) cells, which is superior to 5-aminolevulinic acid, a known photodynamic compound. For in vivo experiments solid tumor was induced using EAC cells in the male Swiss albino mice of groups I, II, III and IV. Group I served as the control (without solid tumor), group II served as tumor bearing mice without treatment and groups III and IV served as treatments. At the completion of 4 weeks of induction, the tumor bearing mice from group III and IV were given an intraperitoneal injection with embelin (12.5mg/kg body weight). After 24h, tumor area in the Group III and IV animals was exposed to visible light from a 1,000 W halogen lamp. The mice from groups I to III were sacrificed 2 weeks after the PDT treatment and the marker enzymes (myeloperoxidase [MPO], ß-d-glucuronidase, and rhodanese) were assayed and expression of Bcl-2 and Bax were analyzed in normal and tumor tissues. Animals from group IV were sacrificed after 90 days of PDT treatment and the above mentioned parameters were recorded. Reduction in tumor volume and reversal of biochemical markers to near normal levels were observed in the treated groups. This is the first report on PDT using a natural compound for solid tumor control in vivo. The uniqueness of the mode of treatment lies in the selective uptake of the nontoxic natural compound, embelin from the medicinal plant E. ribes used in Indian system of medicine, by the solid tumor cells and their selective destruction using PDT without affecting the neighboring normal cells, which is much advantageous over radiation therapy now frequently used.