Bakkenolide G, a natural PAF-receptor antagonist

A review on the ethnobotany, phytochemistry, pharmacology and toxicology of butterbur species (Petasites L.)

ETHNOPHARMACOLOGICAL RELEVANCE

Petasites (butterbur, Asteraceae) species have been used since Ancient times in the traditional medicine of Asian and European countries to treat central nervous system (migraine), respiratory (asthma, allergic rhinitis, bronchitis, spastic cough), cardiovascular (hypertension), gastrointestinal (ulcers) and genitourinary (dysmenorrhea) disorders.

AIM OF THE REVIEW

This study summarized and discussed the traditional uses, phytochemical, pharmacological and toxicological aspects of Petasites genus.

MATERIALS AND METHODS

A systematic search of Petasites in online databases (Scopus, PubMed, ScienceDirect, Google Scholar) was performed, with the aim to find the phytochemical, toxicological and bioactivity studies. The Global Biodiversity Information Facility, Plants of the World Online, World Flora Online and The Plant List databases were used to describe the taxonomy and geographical distribution.

RESULTS

The detailed phytochemistry of the potentially active compounds of Petasites genus (e.g. sesquiterpenes, pyrrolizidine alkaloids, polyphenols and essential oils components) was presented. The bioactivity studies (cell-free, cell-based, animal, and clinical) including the traditional uses of Petasites (e.g. anti-spasmolytic, hypotensive, anti-asthmatic activities) were addressed and followed by discussion of the main pharmacokinetical and toxicological issues related to the administration of butterbur-based formulations.

CONCLUSIONS

This review provides a complete overview of the Petasites geographical distribution, traditional use, phytochemistry, bioactivity, and toxicity. More than 200 different sesquiterpenes (eremophilanes, furanoeremophilanes, bakkenolides), 50 phenolic compounds (phenolic acids, flavonoids, lignans) and volatile compounds (monoterpenes, sesquiterpenes) have been reported within the genus. Considering the phytochemical complexity and the polypharmacological potential, there is a growing research interest to extend the current therapeutical applications of Petasites preparations (anti-migraine, anti-allergic) to other human ailments, such as central nervous system, cardiovascular, malignant or microbial diseases. This research pathway is extremely important, especially in the recent context of the pandemic situation, when there is an imperious need for novel drug candidates.

Applications of alkyl orthoesters as valuable substrates in organic transformations, focusing on reaction media

In this review we focus on applications of alkyl orthoesters as valuable and efficient substrates to perform various classes of two-component and multi-component organic reactions. The article has classified them according to two aspects, which are: (i) a focus on the reaction medium (solvent-free conditions, aqueous media, and organic solvents); and (ii) an examination of product structures. Reaction accomplishment under solvent-free conditions is an eco-friendly process with the absence of volatile toxic solvents, which puts it in line with green chemistry goals. Water is an interesting choice in organic transformations due to its inexpensiveness and safety. The authors hope their assessment will help chemists to attain new approaches for utilizing alkyl orthoesters in various organic synthetic methods. The review covers the corresponding literature up to the beginning of 2020.

In this review we focus on applications of alkyl orthoesters as valuable and efficient substrates to perform various classes of two-component and multi-component organic reactions.

Petatewalide B, a novel compound from Petasites japonicus with anti-allergic activity

ETHNOPHARMACOLOGICAL RELEVANCE

The giant butterbur Petasites japonicus is used to treat asthma and allergic diseases in traditional Korean, Japanese, and Chinese medicine.

AIM OF THE STUDY

To elucidate the anti-allergic effect of Petasites genus, we studied effects of several compounds from Petasites japonicus leaves and found a novel bakkenolide-type sesquiterpine. In the present study, anti-allergic and anti-inflammatory effects of the new compound was examined using in vivo and in vitro experiments.

MATERIALS AND METHODS

The novel compound was isolated from Petasites japonicus leaves and named petatewalide B. Antigen-induced degranulation and Ca(2+) mobilization were measured in RBL-2H3 mast cells by measuring β-hexosaminidase activity and fluorescence change of Ca(2+) probe, fura-2. Induction of inducible nitric oxide synthase and cyclooxygenase 2 was measured by Western blotting in peritoneal macrophages. In addition, ovalbumin-induced asthma model was used for in vivo efficacy test of petatewalide B. Membrane potential was estimated by measuring fluorescence change of DiBAC in C6 glioma cells.

RESULTS

Petatewalide B inhibited the antigen-induced degranulation of β-hexosaminidase in RBL-2H3 mast cells, but did not affect antigen-induced Ca(2+) increase in the cells. Petatewalide B also showed inhibition of the LPS-induced induction of iNOS, but not COX-2 in mouse peritoneal macrophages. Nitric oxide production was also inhibited by petatewalide B in macrophages. In the ovalbumin-induced asthma model, petatewalide B strongly inhibited accumulations of eosinophils, macrophages, and lymphocytes in bronchoalveolar lavage fluid. Petatewalide B increased the membrane potential of C6 glioma cells in a concentration-dependent manner.

CONCLUSION

Petatewalide B from Petasites genus not only has anti-allergic and anti-inflammatory effects but also induces a transient increase of membrane potential in C6 glioma cells.

Anti-allergic and anti-inflammatory effects of bakkenolide B isolated from Petasites japonicus leaves

AIMS OF THE STUDY

To elucidate the anti-allergic and anti-inflammatory effects of Petasites genus, we studied the effects of several compounds isolated from Petasites japonicas leaves.

MATERIALS AND METHODS

Bakkenolide B was isolated from Petasites japonicus leaves. Antigen-induced degranulation was measured in RBL-2H3 mast cells by measuring β-hexosamidase activity. Induction of inducible nitric oxide synthase and cyclooxygenase 2 was measured by Western blotting in peritoneal macrophages. Ovalbumin-induced asthma model was used for in vivo efficacy test of bakkanolide B.

RESULTS

We found that bakkenolide B, a major component of the leaves, concentration-dependently inhibited RBL-2H3 mast cell degranulation. Bakkenolide B also inhibited the gene inductions of inducible nitric oxide synthase and cyclooxygenase 2 in mouse peritoneal macrophages. Furthermore, in an ovalbumin-induced asthma model, bakkenolide B strongly inhibited the accumulation of eosinophils, macrophages, and lymphocytes to bronchoalveolar lavage fluid.

CONCLUSION

Bakkenolide B has suppressive properties for allergic and inflammatory responses and may be utilized as a potent agent for the treatment of asthma.

Platelet-activating factor (PAF)-antagonists of natural origin

Presently herbal medicines are being used by about 80% of the world population for primary health care as they stood the test of time for their safety, efficacy, cultural acceptability and lesser side effects. The discovery of platelet activating factor antagonists (PAF antagonists) during these decades are going on with different framework, but the researchers led their efficiency in studying in vitro test models. Since it is assumed that PAF play a central role in etiology of many diseases in humans such as asthma, neuronal damage, migraine, cardiac diseases, inflammatory, headache etc. Present days instinctively occurring PAF antagonist exists as a specific grade of therapeutic agents for the humans against these and different diseases either laid hold of immunological or non-immunological types. Ginkgolide, cedrol and many other natural PAF antagonists such as andrographolide, α-bulnesene, cinchonine, piperine, kadsurenone, different Piper species' natural products and marine origin plants extracts or even crude drugs having PAF antagonist properties are being used currently against different inflammatory pathologies. This review is an attempt to summarize the data on PAF and action of natural PAF antagonists on it, which were evaluated by in vivo and in vitro assays.

Understanding the regulation mechanisms of PAF receptor by agonists and antagonists: Molecular modeling and molecular dynamics simulation studies

Platelet-activating factor receptor (PAFR) is a member of G-protein coupled receptor (GPCR) superfamily. Understanding the regulation mechanisms of PAFR by its agonists and antagonists at the atomic level is essential for designing PAFR antagonists as drug candidates for treating PAF-mediated diseases. In this study, a 3D model of PAFR was constructed by a hierarchical approach integrating homology modeling, molecular docking and molecular dynamics (MD) simulations. Based on the 3D model, regulation mechanisms of PAFR by agonists and antagonists were investigated via three 8-ns MD simulations on the systems of apo-PAFR, PAFR-PAF and PAFR-GB. The simulations revealed that binding of PAF to PAFR triggers the straightening process of the kinked helix VI, leading to its activated state. In contrast, binding of GB to PAFR locks PAFR in its inactive state.

α-Bulnesene, a PAF inhibitor isolated from the essential oil of Pogostemon cablin

Steam distilled essential oil from the aerial parts of Pogostemon cablin was analyzed by gas chromatography-mass spectrometry (GC-MS). Forty one compounds were identified of which alpha-guaiene (20.62%) and alpha-bulnesene (16.18%) were major constituents. Furthermore, fractionation of the essential oil from P. cablin guided by inhibitory activity against PAF-induced platelet aggregation led to the isolation of the sesquiterpene, alpha-bulnesene.

A Novel Phenylpropenoyl Sulfonic Acid and a New Chlorophyll from the Leaves of Petasites formosanus KITAMURA

A novel phenylpropenoyl sulfonic acid, petasiformin-A (1), and a new chlorophyll, petasiphyll-A (2), were isolated from the leaves of Petasites formosanus KITAMURA (Compositae). Their structures were established by spectral and chemical transformation methods. Petasiformin-A (1) showed the significant antioxidative activity in DPPH radical scavenging assay.

Novel agents in the therapy of endotoxic shock

Endotoxic shock, or Gram-negative septic shock, can occur as a component of Gram-negative sepsis and is characterised by hypotension, poor tissue perfusion and multi-organ dysfunction. Despite antibiotic therapy and intensive care management, the morbidity and mortality rates of Gram-negative septic shock remain high. Endotoxin mediates its effects through interaction with receptors on the surface of a variety of host cells. These interactions result in the production and release of numerous biochemical mediators including nitric oxide, cytokines, prostaglandins and leukotrienes and toxic oxygen radicals. It is these biochemical mediators that exert toxic effects during endotoxic shock and which are often the target of novel treatment strategies. Several of these pharmacological agents are currently being investigated for use in Gram-negative septic shock and include inhibitors of the enzyme responsible for nitric oxide production, scavengers of the nitric oxide molecule and cytokine modulators. Although many agents have been studied for potential use as modulators of cytokine levels, this study will focus on pentoxifylline and the 21-aminosteroids, or lazaroids. Examination of the literature regarding pharmacological agents used to treat endotoxic shock often yields confusing and contradictory results. The reasons for these mixed results include differences in models, drug dosages, dosing methods and intervals and timing of administration relative to disease duration and severity. However, despite mixed results, several of the drugs discussed in this paper offer promise in the therapy of an often frustrating and lethal condition.