Evaluation of Jatropha isabelli natural products and their synthetic analogs as potential antimalarial therapeutic agents

Phytochemical Characterization and In Vitro Anti-Inflammatory Evaluation in RAW 264.7 Cells of Jatropha cordata Bark Extracts

The inflammatory process, although beneficial, can produce tissue damage and systemic damage when uncontrolled. Effective therapeutic alternatives with little or no side effects are of great therapeutic interest. This study aimed to determine the phytochemical composition of bark extracts from J. cordata, an endemic plant from México, and evaluate their in vitro anti-inflammatory activity. Hexane, ethyl acetate, and methanol extracts were characterized by qualitative phytochemical tests, and their bioactive groups were identified by ¹H NMR and gas chromatography coupled to mass spectrometry (GC-MS). The extract's anti-inflammatory activity was evaluated as nitric oxide (NO) production and their cytotoxicity by an MTS cell proliferation assay in lipopolysaccharide (LPS)-activated RAW 264.7 cells at concentrations of 1-100 μg/mL. The hexane extract contained fatty acids, fatty esters, phytosterols, alkanes, vitamin E, and terpenoids; the ethyl acetate extract showed fatty acids, fatty esters, aromatic aldehyde, phytosterols, vitamin E, and terpenoids, while the methanolic extract showed fatty esters, fatty acid, aromatics aldehydes, and alcohol. The ethyl acetate extract showed the highest inhibition of NO production, followed by the methanolic extract and the hexane extract, without affecting the viability of RAW 264.7 macrophage cells. The results suggest that J. cordata extracts are a potential source of bioactive compounds with anti-inflammatory potential.

A facile approach to spiro[dihydrofuran-2,3'-oxindoles] via formal [4 + 1] annulation reaction of fused 1H-pyrrole-2,3-diones with diazooxindoles

There has been developed an easy synthetic approach to spiro[dihydrofuran-2,3'-oxindoles] via a highly diastereoselective formal [4 + 1] cycloaddition reaction of [e]-fused 1H-pyrrole-2,3-diones with diazooxindoles. The described novel heterocyclic systems are heteroanalogues of antimicrobial and antibiofilm fungal metabolites. The developed reaction represents the first example of involving 1H-pyrrole-2,3-diones fused at the [e]-side in a [4 + 1] annulation reaction.

Antimalarial Activity of Extract and Fractions of Sauropus androgynus (L.) Merr

Sauropus androgynus (L.) Merr., in the Indonesian local name known as "Katuk," is a tropical shrub plant of the family Euphorbiaceae. Based on genus and chemotaxonomic approaches, as well as in vitro testing of Plasmodium falciparum, leaves of S. androgynus are presumed to have an active compound content as an antimalarial. The current study aims to investigate the antimalarial activity of 96% ethanol extract and fractions of S. androgynus leaves. The ethanolic extract was fractionated using the vacuum liquid chromatography (VLC) method with three solvents of different polarities (n-hexane, chloroform, and 96% ethanol). The fraction obtained was then evaluated for antimalarial activity against P. falciparum 3D7 strain. The ethanolic extract was evaluated for antimalarial suppressive and prophylactic activity against P. berghei-infected mice, as well as inhibitory activity against the heme detoxification process in vitro. Fractionation of ethanolic extract resulted in seven combined fractions, with the most active fraction being FV (50% inhibitory concentration (IC₅₀) = 2.042 µg/mL). The ethanolic extract showed good parasitic suppressive (therapeutic) activity with a median effective dose (ED₅₀) value of 15.35 mg/kg body weight. In a prophylactic test, ethanolic extract showed parasite growth inhibitory activity of 67.74 ± 9.21% after the administration of 400 mg/kg body weight for 4 days before infection, and 65.30 ± 10.44% after the administration of 200 mg/kg body weight for 8 consecutive days (4 days before and after infection). The ethanolic extract also showed an effect in inhibiting the formation of β-hematin of about 26.87-79.36% at a concentration of 0.1-4 mg/mL and an IC₅₀ value of 0.479 mg/mL. The S. androgynus leaves were shown to have antimalarial activity in vitro and in vivo, where ethanolic extract were more active compared with the fraction obtained. The antimalarial properties of the extract showed a higher suppressive activity than prophylactic activity.

Engineering Production of a Novel Diterpene Synthase Precursor in Nicotiana benthamiana

Diterpene biosynthesis commonly originates with the methylerythritol phosphate (MEP) pathway in chloroplasts, leading to the C₂₀ substrate, geranylgeranyl pyrophosphate (GGPP). The previous work demonstrated that over-expression of genes responsible for the first and last steps in the MEP pathway in combination with GERANYLGERANYL PYROPHOSPHATE SYNTHASE (GGPPS) and CASBENE SYNTHASE (CAS) is optimal for increasing flux through to casbene in Nicotiana benthamiana. When the gene responsible for the last step in the MEP pathway, 4-HYDROXY-3-METHYLBUT-2-ENYL DIPHOSPHATE REDUCTASE (HDR), is removed from this combination, casbene is still produced but at lower amounts. Here, we report the unexpected finding that this reduced gene combination also results in the production of 16-hydroxy-casbene (16-OH-casbene), consistent with the presence of 16-hydroxy-geranylgeranyl phosphate (16-OH-GGPP) in the same material. Indirect evidence suggests the latter is formed as a result of elevated levels of 4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) caused by a bottleneck at the HDR step responsible for conversion of HMBPP to dimethylallyl pyrophosphate (DMAPP). Over-expression of a GERANYLLINALOOL SYNTHASE from Nicotiana attenuata (NaGLS) produces 16-hydroxy-geranyllinalool (16-OH-geranyllinalool) when transiently expressed with the same reduced combination of MEP pathway genes in N. benthamiana. This work highlights the importance of pathway flux control in metabolic pathway engineering and the possibility of increasing terpene diversity through synthetic biology.

Anti-viral activity of jatrophone against RSV-induced respiratory infection via increase in interferon-γ generating dendritic cells

Respiratory syncytial virus (RSV), a member of Paramyxoviridae family is responsible for bronchiolitis and pneumonia. The present study investigated anti-viral and anti-inflammatory activities of jatrophone against RSV-infection in pulmonary epithelial cells in vitro and in mice model in vivo. The changes in viabilities of RSV infected cells by jatrophone treatment were determined by MTT assay. The fluorescence associated with production of ROS was evaluated by fluorescence microscopy using H2DCFDA dye. The IFN-γ secreting cells were detected in mice BALF by stimulation with phorbol myristate acetate and ionomycin. The reduction of BEAS-2B cell viability by RSV was alleviated on treatment with jatrophone in dose based manner. The cytopathogenic changes by RSV infection were prevented and viral growth inhibited by jatrophone in BEAS-2B cells. Jatrophone treatment significantly alleviated RSV mediated overproduction of IL-6/-8 and suppressed ROS generation in the cells. The pulmonary viral titers were found to be markedly lower in mice treated with jatrophone relative to untreated group. The jatrophone treated mice also showed reduced IL-4/-5/-13 levels and elevated IFN-γ level in BALF relative to untreated RSV infected mice. Flow cytometry revealed elevated count of IFN-γ generating cells in RSV infected mice on treatment with jatrophone. Thus jatrophone inhibits viral growth and oxidative damage by RSV in pulmonary epithelial cells. In RSV infected mice jatrophone increased immunity for viral infection by modulating cell phenotype for promotion of anti-viral IFN-γ. Thus jatrophone acts as potential anti-viral compound and may be developed for treatment of respiratory treat infection.

The genus Jatropha (Euphorbiaceae): A review on secondary chemical metabolites and biological aspects

The genus Jatropha belongs to the Euphorbiaceae family and has about 175 species. Originally from tropical America, the Jatropha genus can be found all over the tropics and subtropics of Asia and Africa. Jatropha species are recognized to be important sources of secondary metabolites with a broad spectrum of biological functions. Extracts and isolated compounds from species of this genus have been known to have properties of cytotoxicity, antimicrobial, antifungal, anti-inflammatory, antioxidant, insecticidal, larvicidal, inhibition AChE, and toxicity activities. Investigations on the chemical aspects of the genus Jatropha have led to the identification of cyclic peptides, lignans, flavonoids, coumarins, alkaloids, eudesmenoic acids, and mainly terpenes. In this review, we provide a comprehensive picture of the phytochemical and biological characteristics of Jatropha species. The information gathered and approached in this paper might support the planning and discussion of future studies on the topic.

Cytostatic and Cytotoxic Natural Products against Cancer Cell Models

The increasing prevalence of drug resistant and/or high-risk cancers indicate further drug discovery research is required to improve patient outcome. This study outlines a simplified approach to identify lead compounds from natural products against several cancer cell lines, and provides the basis to better understand structure activity relationship of the natural product cephalotaxine. Using high-throughput screening, a natural product library containing fractions and pure compounds was interrogated for proliferation inhibition in acute lymphoblastic leukemia cellular models (SUP-B15 and KOPN-8). Initial hits were verified in control and counter screens, and those with EC₅₀ values ranging from nanomolar to low micromolar were further characterized via mass spectrometry, NMR, and cytotoxicity measurements. Most of the active compounds were alkaloid natural products including cephalotaxine and homoharringtonine, which were validated as protein synthesis inhibitors with significant potency against several cancer cell lines. A generated BODIPY-cephalotaxine probe provides insight into the mode of action of cephalotaxine and further rationale for its weaker potency when compared to homoharringtonine. The steroidal natural products (ecdysone and muristerone A) also showed modest biological activity and protein synthesis inhibition. Altogether, these findings demonstrate that natural products continue to provide insight into structure and function of molecules with therapeutic potential against drug resistant cancer cell models.

Studies of Jatrogossone A as a Reactive Oxygen Species Inducer in Cancer Cellular Models

Natural products continue to provide a platform to study biological systems. A bioguided study of cancer cell models led us to a new member of the jatrophane natural products from Jatropha gossypiifolia, which was independently identified and characterized as jatrogossone A (1). Purification and structure elucidation was performed by column chromatography and high-performance liquid chromatography-mass spectrometry and NMR techniques, and the structure was confirmed via X-ray crystallography. The unique molecular scaffold of jatrogossone A prompted an evaluation of its mode of action. Cytotoxicity assays demonstrated that jatrogossone A displays selective antiproliferative activity against cancer cell models in the low micromolar range with a therapeutic window. Jatrogossone A (1) affects mitochondrial membrane potential (ΔΨm) in a time- and dose-dependent manner. This natural product induces radical oxygen species (ROS) selectively in cancer cellular models, with minimal ROS induction in noncancerous cells. Compound 1 induces ROS in the mitochondria, as determined by colocalization studies, and it induces mitophagy. It promotes also in vitro cell death by causing cell arrest at the G2/M stage, caspase (3/7) activation, and PARP-1 cleavage. The combined findings provide a potential mechanism by which 1 relies on upregulation of mitochondrial ROS to potentiate cytotoxic effects through intracellular signaling.

Antimalarial Activity of Plant Metabolites

Malaria, as a major global health problem, continues to affect a large number of people each year, especially those in developing countries. Effective drug discovery is still one of the main efforts to control malaria. As natural products are still considered as a key source for discovery and development of therapeutic agents, we have evaluated more than 2000 plant extracts against Plasmodium falciparum. As a result, we discovered dozens of plant leads that displayed antimalarial activity. Our phytochemical study of some of these plant extracts led to the identification of several potent antimalarial compounds. The prior comprehensive review article entitled “Antimalarial activity of plant metabolites” by Schwikkard and Van Heerden (2002) reported structures of plant-derived compounds with antiplasmodial activity and covered literature up to the year 2000. As a continuation of this effort, the present review covers the antimalarial compounds isolated from plants, including marine plants, reported in the literature from 2001 to the end of 2017. During the span of the last 17 years, 175 antiplasmodial compounds were discovered from plants. These active compounds are organized in our review article according to their plant families. In addition, we also include ethnobotanical information of the antimalarial plants discussed.

The natural compound Jatrophone interferes with Wnt/β-catenin signaling and inhibits proliferation and EMT in human triple-negative breast cancer

Metastatic breast cancer is the leading cause of worldwide cancer-related deaths among women. Triple negative breast cancers (TNBC) are highly metastatic and are devoid of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) amplification. TNBCs are unresponsive to Herceptin and/or anti-estrogen therapies and too often become highly chemoresistant when exposed to standard chemotherapy. TNBCs frequently metastasize to the lung and brain. We have previously shown that TNBCs are active for oncogenic Wnt10b/β-catenin signaling and that WNT10B ligand and its downstream target HMGA2 are predictive of poorer outcomes and are strongly associated with chemoresistant TNBC metastatic disease. In search of new chemicals to target the oncogenic WNT10B/β-CATENIN/HMGA2 signaling axis, the anti-proliferative activity of the diterpene Jatrophone (JA), derived from the plant Jatropha isabelli, was tested on TNBC cells. JA interfered with the WNT TOPFLASH reporter at the level between receptor complex and β-catenin activation. JA efficacy was determined in various subtypes of TNBC conventional cell lines or in TNBC cell lines derived from TNBC PDX tumors. The differential IC₅₀ (DCI₅₀) responsiveness was compared among the TNBC models based on etiological-subtype and their cellular chemoresistance status. Elevated WNT10B expression also coincided with increased resistance to JA exposure in several metastatic cell lines. JA interfered with cell cycle progression, and induced loss of expression of the canonical Wnt-direct targets genes AXIN2, HMGA2, MYC, PCNA and CCND1. Mechanistically, JA reduced steady-state, non-phosphorylated (activated) β-catenin protein levels, but not total β-catenin levels. JA also caused the loss of expression of key EMT markers and significantly impaired wound healing in scratch assays, suggesting a direct role for JA inhibiting migration of TNBC cells. These results indicate that Jatrophone could be a powerful new chemotherapeutic agent against highly chemoresistant triple negative breast cancers by targeting the oncogenic Wnt10b/β-catenin signaling pathway.

Microbial transformation of methyl cyperenoate by Cunninghamella elegans AS 3.2028 and the antithrombotic activities of its metabolites

Microbial transformation is a remarkable tool for the structural modification of bioactive natural compounds converting them into more valuable biologically active derivatives.

Plants as antimalarial agents in Sub-Saharan Africa

Although the burden of malaria is decreasing, parasite resistance to current antimalarial drugs and resistance to insecticides by vector mosquitoes threaten the prospects of malaria elimination in endemic areas. Corollary, there is a scientific departure to discover new antimalarial agents from nature. Because the two antimalarial drugs quinine and artemisinin were discovered through improved understanding of the indigenous knowledge of plants, bioprospecting Sub-Saharan Africa's enormous plant biodiversity may be a source of new and better drugs to treat malaria. This review analyses the medicinal plants used to manage malaria in Sub-Saharan Africa. Chemical compounds with antiplasmodial activity are described. In the Sub-Saharan African countries cited in this review, hundreds of plants are used as antimalarial remedies. While the number of plant species is not exhaustive, plants used in more than one country probably indicate better antimalarial efficacy and safety. The antiplasmodial data suggest an opportunity for inventing new antimalarial drugs from Sub-Saharan-African flora.

Antimalarial activity of abietane ferruginol analogues possessing a phthalimide group

The abietane-type diterpenoid (+)-ferruginol, a bioactive compound isolated from New Zealand's Miro tree (Podocarpus ferruginea), displays relevant pharmacological properties, including antimicrobial, cardioprotective, anti-oxidative, anti-plasmodial, leishmanicidal, anti-ulcerogenic, anti-inflammatory and anticancer. Herein, we demonstrate that ferruginol (1) and some phthalimide containing analogues 2-12 have potential antimalarial activity. The compounds were evaluated against malaria strains 3D7 and K1, and cytotoxicity was measured against a mammalian cell line panel. A promising lead, compound 3, showed potent activity with an EC50 = 86 nM (3D7 strain), 201 nM (K1 strain) and low cytotoxicity in mammalian cells (SI>290). Some structure-activity relationships have been identified for the antimalarial activity in these abietane analogues.

Production of bioactive diterpenoids in the euphorbiaceae depends on evolutionarily conserved gene clusters

The Euphorbiaceae produce a diverse range of diterpenoids, many of which have pharmacological activities. These diterpenoids include ingenol mebutate, which is licensed for the treatment of a precancerous skin condition (actinic keratosis), and phorbol derivatives such as resiniferatoxin and prostratin, which are undergoing investigation for the treatment of severe pain and HIV, respectively. Despite the interest in these diterpenoids, their biosynthesis is poorly understood at present, with the only characterized step being the conversion of geranylgeranyl pyrophosphate into casbene. Here, we report a physical cluster of diterpenoid biosynthetic genes from castor (Ricinus communis), including casbene synthases and cytochrome P450s from the CYP726A subfamily. CYP726A14, CYP726A17, and CYP726A18 were able to catalyze 5-oxidation of casbene, a conserved oxidation step in the biosynthesis of this family of medicinally important diterpenoids. CYP726A16 catalyzed 7,8-epoxidation of 5-keto-casbene and CYP726A15 catalyzed 5-oxidation of neocembrene. Evidence of similar gene clustering was also found in two other Euphorbiaceae, including Euphorbia peplus, the source organism of ingenol mebutate. These results demonstrate conservation of gene clusters at the higher taxonomic level of the plant family and that this phenomenon could prove useful in further elucidating diterpenoid biosynthetic pathways.