Patterns of Plumericin Concentration in Leaves of Himatanthus tarapotensis (Apocynaceae) and Its Interactions with Herbivory in the Peruvian Amazon.

We explored the concentration patterns of the bioactive metabolite plumericin produced by Himatanthus tarapotensis (Apocynaceae) under different edaphic conditions and variations in rainfall intensity, as well as its potential role in the chemical defense against insect herbivores. Values of plumericin concentration from leaves were obtained by High-Performance Liquid Chromatography, and evaluated as a function of differences in soil types, variation of precipitation, and variation of the abundance of insect herbivores, using first a Repeated Measures Correlation (rmcorr) and then a Generalized Linear Mixed Model (GLMM) analysis. Plumericin concentration is highly variable among plants, but with a significantly higher concentration in plants growing on clay soil compared to that of the white-sand soil habitat (p < 0.001). Plumericin concentration is not affected by precipitation. The caterpillar of Isognathus leachii (Lepidoptera: Sphingidae) is the most conspicuous herbivore of H. tarapotensis, and its presence is continuous but not related to plumericin concentration, probably because of its capacity to elude the chemical defense of this plant. Nevertheless, our multivariate model revealed that plumericin concentration is related to the abundance of Hymenoptera (Formicidae), and this relationship is significantly influenced by the soil parameters of carbon percentage, clay percentage, and phosphorous percentage (p < 0.001). Plumericin is a mediating agent in the interaction between H. tarapotensis and its natural environment. Variation in plumericin concentration would be induced by the abundance of Hymenoptera (Formicidae), probably as a chemical response against these insects, and by differences in soil nutrient availability.

Plumericin Protects against Experimental Inflammatory Bowel Disease by Restoring Intestinal Barrier Function and Reducing Apoptosis.

Intestinal epithelial barrier impairment plays a key pathogenic role in inflammatory bowel diseases (IBDs). In particular, together with oxidative stress, intestinal epithelial barrier alteration is considered as upstream event in ulcerative colitis (UC). In order to identify new products of natural origin with a potential activity for UC treatment, this study evaluated the effects of plumericin, a spirolactone iridoid, present as one of the main bioactive components in the bark of Himatanthus sucuuba (Woodson). Plumericin was evaluated for its ability to improve barrier function and to reduce apoptotic parameters during inflammation, both in intestinal epithelial cells (IEC-6), and in an animal experimental model of 2, 4, 6-dinitrobenzene sulfonic acid (DNBS)-induced colitis. Our results indicated that plumericin increased the expression of adhesion molecules, enhanced IEC-6 cells actin cytoskeleton rearrangement, and promoted their motility. Moreover, plumericin reduced apoptotic parameters in IEC-6. These results were confirmed in vivo. Plumericin reduced the activity of myeloperoxidase, inhibited the expression of ICAM-1, P-selectin, and the formation of PAR, and reduced apoptosis parameters in mice colitis induced by DNBS. These results support a pharmacological potential of plumericin in the treatment of UC, due to its ability to improve the structural integrity of the intestinal epithelium and its barrier function.

Plumeria rubra L.- A review on its ethnopharmacological, morphological, phytochemical, pharmacological and toxicological studies.

ETHNOPHARMACOLOGICAL RELEVANCE: Plumeria rubra L. (Apocynaceae) is a deciduous, commonly ornamental, tropical plant grown in home premises, parks, gardens, graveyards, because of its beautiful and attractive flowers of various colours and size. The different parts of the plant are used traditionally to treat various diseases and conditions like leprosy, inflammation, diabetic mellitus, ulcers, wounds, itching, acne, toothache, earache, tongue cleaning, pain, asthma, constipation and antifertility. AIM OF THE REVIEW: The main aim of this review is to provide an overview and critically analyze the reported ethnomedical uses, phytochemistry, pharmacological activities and toxicological studies of P. rubra and to identify the remaining gaps and thus supply a basis for further investigations. The review also focuses towards drawing attention of people and researchers about the wide spread pharmaceutical properties of the plant for its better utilization in the coming future. MATERIAL AND METHODS: All the relevant data and information on P. rubra was gathered using various databases such as PubMed, Springer, Taylor and Francis imprints, NCBI (National Center for Biotechnology Information), Science direct, Google scholar, Chemspider, SciFinder, research and review articles from peer-reviewed journals and unpublished data such as Phd thesis, etc. Some other 'grey literature' sources such as webpages, ethnobotanical books, chapters, wikipedia were also studied. RESULTS: More than 110 chemical constituents have been isolated from P. rubra including iridoids, terpenoids, flavonoids and flavonoid glycosides, alkaloids, glycosides, fatty acid esters, carbohydrates, animo acids, lignan, coumarin, volatile oils, etc. The important chemical constituents responsible for pharmacological activities of the plant are fulvoplumierin, plumieride, rubrinol, lupeol, oleanolic acid, stigmasterol, taraxasteryl acetate, plumieride-p-E-coumarate, rubranonoside, rubrajalellol, plumericin, isoplumericin, etc. The plant possess a wide range of pharmacological activities present namely antibacterial, antiviral, anti-inflammatory, antipyretic, antidiabetic, hepatoprotective, anticancer, anthelmintic, antifertility and many other activities. CONCLUSION: P. rubra is a valuable medicinal source and further study in this topic can validate the traditional and ethnobotanical use of the plant. However, many aspects of the plant have not been studied yet. The pharmacological activity of active chemical constituent isolated from the plant is proven only for a couple of activities hence, lack of bio-guided isolation strategies is observed. Further studies on bioavailability, pharmacokinetics, mechanism of action and structural activity relationship studies of isolated pure compounds will contribute more in understanding their pharmacological effects. Higher doses of plant extracts are administered to experimental animals, therefore their toxicity and side effects in humans are needed to be thoroughly studied, although no side effect or toxicity is seen or observed in experimental animals. Studies are also essential to investigate the long term in vivo toxicity and clinical efficacy of the plant.

Plumericin prevents intestinal inflammation and oxidative stress in vitro and in vivo.

Inflammatory bowel diseases (IBDs) are characterized by an inflammatory and oxidative stress condition in the intestinal tissue. In this study, we evaluated the effect of plumericin, one of the main bioactive components of Himatanthus sucuuba (Woodson) bark, on intestinal inflammation and oxidative stress, both in vitro and in vivo. The effect of plumericin (0.5-2 µM) in vitro was evaluated in rat intestinal epithelial cells (IEC-6) treated with lipopolysaccharides from E. coli (10 µg/mL) plus interferon-γ (10 U/mL). Moreover, a 2,4,6-dinitrobenzene sulfonic acid (DNBS)-induced colitis model was used to evaluate the anti-inflammatory and antioxidant activity of plumericin (3 mg/kg) in vivo. The results showed that plumericin significantly reduces intestinal inflammatory factors such as tumor necrosis factor-α, cyclooxygenase-2 and inducible nitric oxide synthase expression, and nitrotyrosine formation. Plumericin also inhibited nuclear factor-κB translocation, reactive oxygen species (ROS) release, and inflammasome activation. Moreover, plumericin activated the nuclear factor erythroid-derived 2 pathway in IEC-6. Using the DNBS-induced colitis model, a significant reduction in the weight loss and in the development of the macroscopic and histologic signs of colon injury, together with a reduced inflammatory and oxidative stress state, were observed in plumericin-treated mice. These results indicate that plumericin exerts a strong anti-inflammatory and antioxidant activity. Thus, it might be a candidate for the development of a new pharmacologic approach for IBDs treatment.

Seasonal influence and cytotoxicity of extracts, fractions and major compounds from Allamanda schottii

The aim of this research was to evaluate the fractions obtained from the leaf, stem and roots of Allamanda schottii Pohl, Apocynaceae, responsible for the cytotoxicity, using several cell lines. Cytotoxicity was correlated with the season the part of the plant, and the major compounds were assessed. The ethanol extracts of leaves, stems and roots obtained at different seasons were evaluated in the human erythromyeloblastoid leukemia cell line (K562). Subsequently the ethanol extracts and dichloromethane fractions collected in winter were evaluated in mouse fibroblast cell line (Mus musculus) (L929), cervix adenocarcinoma (HeLa), human pre-B leukemia (Nalm6), as well as K562 cell line. The compounds plumericin, plumieride and ursolic acid isolated from ethanol extracts of the stems were evaluated in the same cell lines, as well as on breast adenocarcinoma cell line (MCF-7), and Mus musculus skin melanoma cell line (B16F10). The chromatographic profiles of the dichloromethane fractions were obtained by high performance liquid chromatography. The results revealed that the season during which A. schottii was collected, and the part of the plant analyzed, influence the cytotoxicity on the K562 cells tested. On the other hand the dichloromethane fractions, mainly from the stems and roots, are responsible for the cytoxicity on the cells tested. These results may be associated with the seasonal variation of plumericin in these parts of the plant. This information is in accordance with the HPLC analysis. The results clearly show the potential for the phytotherapeutic use of this species, and suggest that the cytotoxic activity observed may be due to the presence of plumericin, or to minor compounds not yet identified. The seasonal influence on the production of secondary metabolites was verified.

Identification of plumericin as a potent new inhibitor of the NF-κB pathway with anti-inflammatory activity in vitro and in vivo.

BACKGROUND AND PURPOSE: The transcription factor NF-κB orchestrates many pro-inflammatory signals and its inhibition is considered a promising strategy to combat inflammation. Here we report the characterization of the natural product plumericin as a highly potent inhibitor of the NF-κB pathway with a novel chemical scaffold, which was isolated via a bioactivity-guided approach, from extracts of Himatanthus sucuuba, an Amazonian plant traditionally used to treat inflammation-related disorders. EXPERIMENTAL APPROACH: A NF-κB luciferase reporter gene assay was used to identify NF-κB pathway inhibitors from H. sucuuba extracts. Monitoring of TNF-α-induced expression of the adhesion molecules VCAM-1, ICAM-1 and E-selectin by flow cytometry was used to confirm NF-κB inhibition in endothelial cells, and thioglycollate-induced peritonitis in mice to confirm effects in vivo. Western blotting and transfection experiments were used to investigate the mechanism of action of plumericin. KEY RESULTS: Plumericin inhibited NF-κB-mediated transactivation of a luciferase reporter gene (IC50 1 µM), abolished TNF-α-induced expression of the adhesion molecules VCAM-1, ICAM-1 and E-selectin in endothelial cells and suppressed thioglycollate-induced peritonitis in mice. Plumericin exerted its NF-κB pathway inhibitory effect by blocking IκB phosphorylation and degradation. Plumericin also inhibited NF-κB activation induced by transfection with the constitutively active catalytic subunit of the IκB kinase (IKK-ß), suggesting IKK involvement in the inhibitory action of this natural product. CONCLUSION AND IMPLICATIONS: Plumericin is a potent inhibitor of NF-κB pathways with a new chemical scaffold. It could be further explored as a novel anti-inflammatory lead compound.

Antitumoral, mutagenic and (anti)estrogenic activities of tingenone and pristimerin

Cancer constitutes the second main mortality cause in the world, after cardiovascular diseases. In spite of the progresses in the chemotherapeutics treatments, many patients fail chemotherapy, mainly because of side effects or multi-drugs resistance, proving the need and importance of the research for new molecules with anticancer activity, more effective and with smaller adverse effects. Various compounds derived from plant secondary metabolites are commonly used in the chemotherapy against cancer and the natural products play an important role in the research for new molecules. Among several molecules of natural origin evaluated by MTT assay in murine tumor cell lines [breast (LM3) and lung (LP07)] the quinona-methide triterpenes tingenone and pristimerin showed marked cytotoxic activity presenting IC50 around 2 and 5 µM respectively. The structure-activity relationship suggests that rings A and B containing an α, ß-unsaturated carbonyl group are essential for the observed cytotoxic activity. The interaction between these positions and acetylcisteyne residues suggests a probable mechanism of action. The in vitro mutagenic activity was also evaluated by the Salmonella microsome assay (Ames test) for pristimerin and tingenone with and without metabolic activation (S9) in the strains TA98, TA97a, TA100 and TA102, none of which showed mutagenic potential in any strains. Estrogenic and anti-estrogenic activities were also studied by the e-screen assay in MCF-7 cells with negative results. The present data point to the importance of pristimerin and tingenone as representative of an emerging class of potential anticancer chemicals.