Four anti-protozoal and anti-bacterial compounds from Tapirira guianensis

Undescribed Cyclohexene and Benzofuran Alkenyl Derivatives from Choerospondias axillaris, a Potential Hypoglycemic Fruit

The fruit of Choerospondias axillaris (Anacardiaceae), known as south wild jujube in China, has been consumed widely in several regions of the world to produce fruit pastille and leathers, juice, jam, and candy. A comprehensive chemical study on the fresh fruits led to the isolation and identification of 18 compounds, including 7 new (1-7) and 11 known (8-18) comprised of 5 alkenyl (cyclohexenols and cyclohexenones) derivatives (1-5), 3 benzofuran derivatives (6-8), 6 flavonoids (9-14) and 4 lignans (15-18). Their structures were elucidated by extensive spectroscopic analysis. The known lignans 15-18 were isolated from the genus Choerospondias for the first time. Most of the isolates exhibited significant inhibitory activity on α-glucosidase with IC50 values from 2.26 ± 0.06 to 43.9 ± 0.96 μM. Molecular docking experiments strongly supported the potent α-glucosidase inhibitory activity. The results indicated that C. axillaris fruits could be an excellent source of functional foods that acquire potential hypoglycemic bioactive components.

Stingless Bee (Apidae: Apinae: Meliponini) Ecology

Stingless bees form perennial colonies of honey-making insects. The >600 species of stingless bees, mainly Neotropical, live throughout tropical latitudes. Foragers influence floral biology, plant reproduction, microbe dispersal, and diverse ecosystem functions. As tropical forest residents since the upper Cretaceous, they have had a long evolutionary history without competition from honey bees. Most stingless bees are smaller than any Apis species and recruit nest mates to resources, while their defense strategies exclude stinging behavior but incorporate biting. Stingless bees have diversified ecologically; excel in nesting site selection and mutualisms with plants, arthropods, and microbes; and display opportunism, including co-opting plant defenses. As their biology becomes better known, applications to human endeavors are imposing selective pressures from exploitation and approaches to conservation that entail colony extraction from wildlands. Although some meliponines can adjust to new conditions, their populations shall require tropical diversity for survival and reproduction.

New Alk(en)ylhydroxycyclohexanes with Tyrosinase Inhibition Potential from Harpephyllum caffrum Bernh. Gum Exudate

This work presents the first report on the phytochemical investigation of Harpephyllum caffrum Bernh. gum exudate. A known cardanol, 3-heptadec-12'-Z-enyl phenol (1) and three new alk(en)ylhydroxycyclohexanes, namely, (1R,3R)-1,3-dihydroxy-3-[heptadec-12'(Z)-enyl]cyclohexane (2) (1S,2S,3S,4S,5R)-1,2,3,4,5-pentahydroxy-5-[octadec-13'(Z)-enyl]cyclohexane (3) and (1R,2S,4R)-1,2,4-trihydroxy-4-[heptadec-12'(Z)-enyl]cyclohexane (4) were isolated from the gum. The structures of the compounds were determined by extensive 1D and 2D NMR spectroscopy and HR-ESI-MS data. The ethanolic extract of the gum was found to be the most potent tyrosinase inhibitor with IC₅₀ of 11.32 µg/mL while compounds 2 and 3, with IC₅₀ values of 24.90 and 26.99 µg/mL, respectively, were found to be potential anti-tyrosinase candidates from the gum. Gum exudate may be a potential source for non-destructive harvesting of selective pharmacologically active compounds from plants. The results also provide evidence that H. caffrum gum may find application in cosmetics as a potential anti-tyrosinase agent.

Polyphenol Composition and Antioxidant Activity of Tapirira guianensis Aubl. (Anarcadiaceae) Leaves

Tapirira guianensis (Anacardiaceae) is a natural resource from the Amazonian Forest and is locally known in French Guiana as “loussé” (creole), “tata pilili” (wayãpi), or “ara” (palikur). The tree is used by indigenous populations for medicinal purposes. To increase the potential of this tree for cosmetic, agro-food, or pharmaceutical uses, extracts were obtained through ultrasound-assisted extraction (UAE) from T. guianensis leaves using various extraction solvents such as water, methanol, and methanol–water (85/15; v/v). Chemical (DPPH, TEAC, ORAC) tests were applied to assess the anti-radical potential of these extracts. The polyphenol contents were determined by spectrophotometric (UV/Visible) and by means of chromatographic (UPLC-DAD-ESI-IT-MSⁿ) methods. Tapirira guianensis leaf hydromethanolic extract produced the highest polyphenol content and exhibited antiradical activities in chemical assays (DPPH, TEAC, and ORAC) similar to (or higher than) those of a well-known antiradical plant, green tea. In T. guianensis, two classes of polyphenols were evidenced: (1) galloylquinic acids (identified for the first time in the studied species) and (2) flavonols and flavanols (present in small amounts). Flavonols seemed to play a major role in the antioxidant activity of DPPH. These findings provide a rationale for the use of T. guianensis in traditional medicine and to pave the way for seeking new biological properties involving this Amazonian tree.

Cytotoxicity of Poupartone B, an Alkyl Cyclohexenone Derivative from Poupartia borbonica, against Human Cancer Cell Lines

Poupartia borbonica is an endemic tree from the Mascarene Islands that belongs to the Anacardiaceae family. The leaves of this plant were phytochemically studied previously, and isolated alkyl cyclohexenone derivatives, poupartones A - C, demonstrated antiplasmodial and antimalarial activities. In addition to their high potency against the Plasmodium sp., high toxicity on human cells was also displayed. The present study aims to investigate in more detail the cytotoxicity and pharmacological interest of poupartone B, one of the most abundant derivatives in the leaves of P. borbonica. For that purpose, real-time live-cell imaging of different human cancer cell lines and normal fibroblasts, treated or not treated with poupartone B, was performed. A potent inhibition of cell proliferation associated with the induction of cell death was observed. A detailed morphological analysis of different adherent cell lines exposed to high concentrations of poupartone B (1 - 2 µg/mL) demonstrated that this compound induced an array of cellular alterations, including a rapid retraction of cellular protrusions associated with cell rounding, massive cytoplasmic vacuolization, loss of plasma membrane integrity, and plasma membrane bubbling, ultimately leading to paraptosis-like cell death. The structure-activity relation of this class of compounds, their selective toxicity, and pharmacological potential are discussed.

Anti-mycobacterial and anti-inflammatory activity of restinga plants: a dual approach in searching for new drugs to treat severe tuberculosis

Abstract Tuberculosis (TB) still constitutes a threat to public health in various regions of the world. The existing treatment is long and has many side effects. The need to identify new anti-TB compounds and also adjuvants to control exacerbated inflammation in severe TB cases is relevant. Therefore, the objective of this study was to evaluate the anti-mycobacterial activity of extracts and fractions in vitro from plant species collected in the Restinga of Jurubatiba, in Rio de Janeiro state, Brazil. In addition, to verify their immunomodulatory action and cytotoxicity on macrophages. The dichloromethane fraction of Kielmeyera membranacea and Eremanthus crotonoides showed the lowest MIC50 against Mycobacterium bovis BCG (0.95 ± 1.08 and 2.17 ± 1.11 μg/mL, respectively) and M. tuberculosis H37Rv (4.38 ± 1.19 and 15.28 ± 1.21 μg/mL, respectively). They were also able to inhibit the NO and TNF-α production in LPS-stimulated macrophages, without being toxic to cells. Using gas chromatography analysis coupled with mass spectrometer it was possible to suggest the presence of fatty acids and terpenes in the most promising fractions. Those compounds have been described for their anti-mycobacterial activity. These results have enabled identifying Kielmeyera membranacea and Eremanthus crotonoides as the most promising studied species in searching for new anti-TB compounds with dual activity.

Does Phoradendron perrottetii (mistletoe) alter polyphenols levels of Tapirira guianensis (host plant)?

The present study aimed to investigate the reciprocal effects of Phoradendron perrottetii (mistletoe) and T. guianensis (host plant) regarding their polyphenol composition. Taking into account that tannins are important molecules in plant defense and their biosynthesis tends to be enhanced when a species is exposed to stress, we address the following questions: (1) Are the tannins found in our model species important in the interaction between host and mistletoe? (2) Does the presence of mistletoe induce changes in the content of tannins and other polyphenols in the host plant? (3) Do we find differences between the tannin sub-groups in the responses of the host plant to mistletoe? (4) Could the observed differences reflect the relative importance of one tannin group over another as chemical defense against the mistletoe? Using a polyphenol and tannin group-specific MRM methods we quantified four different tannin sub-groups together with flavonoid and quinic acid derivatives by ultra-performance liquid chromatography tandem mass spectrometry together with the oxidative and protein precipitation activities of leaves and branches of Tapirira guianensis and Phoradendron perrottetii. We selected leaves and branches of six non-parasitized trees of T. guianensis. Leaves and branches of nine individuals of T. guianensis parasitized by P. perrottetii were also sampled. For each parasitized tree, we sampled an infested branch and its leaves, as well as a non-infested branch and its leaves. Infested branches were divided into three groups: gall (the host-parasite interface), proximal, and distal region. Both proanthocyanidins and ellagitanins seem to be important for plant-plant parasitism interaction: host infested tissues (gall and surrounding regions) have clearly less tannin contents than healthy tissues. Mistletoe showed high levels of quinic acid derivatives and flavonoids that could be important during hastorium formation and intrusion on host tissues, suggesting a defense mechanism that could promote oxidative stress together with an inhibition of mistletoe seed germination, consequently avoiding secondary infestations. Polyphenol detected in T. guianensis-P. perrottetii interaction could play different role as plant-mistletoe strategies of survival.

Anti-infective activities of 11 plants species used in traditional medicine in Malaysia

Treatment of drug resistant protozoa, bacteria, and viruses requires new drugs with alternative chemotypes. Such compounds could be found from Southeast Asian medicinal plants. The present study examines the cytotoxic, antileishmanial, and antiplasmodial effects of 11 ethnopharmacologically important plant species in Malaysia. Chloroform extracts were tested for their toxicity against MRC-5 cells and Leishmania donovani by MTT, and chloroquine-resistant Plasmodium falciparum K1 strain by Histidine-Rich Protein II ELISA assays. None of the extract tested was cytotoxic to MRC-5 cells. Extracts of Uvaria grandiflora, Chilocarpus costatus, Tabernaemontana peduncularis, and Leuconotis eugenifolius had good activities against L. donovani with IC₅₀ < 50 μg/mL. Extracts of U. grandiflora, C. costatus, T. peduncularis, L. eugenifolius, A. subulatum, and C. aeruginosa had good activities against P. falciparum K1 with IC₅₀ < 10 μg/mL. Pinoresinol isolated from C. costatus was inactive against L. donovani and P. falciparum. C. costatus extract and pinoresinol increased the sensitivity of Staphylococcus epidermidis to cefotaxime. Pinoresinol demonstrated moderate activity against influenza virus (IC₅₀ = 30.4 ± 11 μg/mL) and was active against Coxsackie virus B3 (IC₅₀ = 7.1 ± 3.0 μg/mL). β-Amyrin from L. eugenifolius inhibited L. donovani with IC₅₀ value of 15.4 ± 0.01 μM. Furanodienone from C. aeruginosa inhibited L. donovani and P. falciparum K1 with IC₅₀ value of 39.5 ± 0.2 and 17.0 ± 0.05 μM, respectively. Furanodienone also inhibited the replication of influenza and Coxsackie virus B3 with IC₅₀ value of 4.0 ± 0.5 and 7.2 ± 1.4 μg/mL (Ribavirin: IC₅₀: 15.6 ± 2.0 μg/mL), respectively. Our study provides evidence that medicinal plants in Malaysia have potentials as a source of chemotypes for the development of anti-infective leads.

Antimalarial Activities of Alkyl Cyclohexenone Derivatives Isolated from the Leaves of Poupartia borbonica

Bioactivity-guided fractionation of the ethyl acetate extract of the leaves of Poupartia borbonica led to the isolation of three new alkyl cyclohexenone derivatives 1-3, and named Poupartone A-C. The structures of the new compounds were elucidated by 1D and 2D NMR spectroscopic data analysis and MS, whereas calculated and experimental ECD spectra were used to define the absolute configurations. These compounds were active against 3D7 and W2 Plasmodium falciparum strains with IC₅₀ values between 0.55 and 1.81 μM. In vitro cytotoxicity against WI38 human fibroblasts and the human cervical cancer cell line HeLa (WST-1 assay) showed that these compounds were also cytotoxic, but no hemolytic activity was observed for the extract and pure compounds. An in vivo antimalarial assay was performed on the major cyclohexenone using P. berghei-infected mice at a dose of 15 mg/kg/day ip. The assay revealed growth inhibition of 59.1 and 69.5% at days 5 and 7 postinfection, respectively, although some toxicity was observed. Zebrafish larvae were used as a model to determine the type of toxicity, and the results showed cardiac toxicity. The methanol extract was also studied, and it displayed moderate antiplasmodial properties in vitro. This extract contained the known flavonoids, quercetin, 3'-O-hydroxysulfonylquercetin, quercitrin, and isoquercitrin as well as ellagic acid, which showed high to low activity against the 3D7 P. falciparum strain.

Phytochemical Study of Tapirira guianensis Leaves Guided by Vasodilatory and Antioxidant Activities

The aim of this research was to perform a phytochemical study of the methanol leaves extract of T. guianensis (MET) guided by vasodilatory and antioxidant activities. The chemical profile of MET and the ethyl acetate fraction (EA fraction) was determined by HPLC-UV-MS and EA fraction guided fractionation by reverse-phase chromatography. The vasorelaxant effects of MET, fractions, sub-fractions and constituents were assessed on rat aorta pre-contracted with phenylephrine. Antioxidant activity was evaluated by using a DPPH assay. The results show that MET-induced vasodilation was dependent on NO/cGMP; and that the PI3K/Akt pathway seems to be the main route involved in eNOS activation. The EA fraction showed greater vasodilatory and antioxidant potency and was submitted to further fractionation. This allowed the isolation and characterization of quercetin, quercetin 3-O-(6″-O-galloyl)-β-d-galactopyranoside and 1,4,6-tri-O-galloyl-β-d-glucose. Also, galloyl-HHDP-hexoside and myricetin deoxyhexoside were identified by HPLC-UV-MS. These compounds are being described for the first time for T. guianensis. 1,4,6-tri-O-galloyl-β-d-glucose and quercetin 3-O-(6″-O-galloyl)-β-d-galactopyranoside showed no vasodilatory activity. Quercetin and myricetin glycoside seems to contribute to the MET activity, since they have been reported as vasodilatory flavonoids. MET-induced vasodilation could contribute to the hypotensive effect of T. guianensis previously reported.

Tapirira guianensis Aubl. Extracts Inhibit Proliferation and Migration of Oral Cancer Cells Lines

Cancer of the head and neck is a group of upper aerodigestive tract neoplasms in which aggressive treatments may cause harmful side effects to the patient. In the last decade, investigations on natural compounds have been particularly successful in the field of anticancer drug research. Our aim is to evaluate the antitumor effect of Tapirira guianensis Aubl. extracts on a panel of head and neck squamous cell carcinoma (HNSCC) cell lines. Analysis of secondary metabolites classes in fractions of T. guianensis was performed using Nuclear Magnetic Resonance (NMR). Mutagenicity effect was evaluated by Ames mutagenicity assay. The cytotoxic effect, and migration and invasion inhibition were measured. Additionally, the expression level of apoptosis-related molecules (PARP, Caspases 3, and Fas) and MMP-2 was detected using Western blot. Heterogeneous cytotoxicity response was observed for all fractions, which showed migration inhibition, reduced matrix degradation, and decreased cell invasion ability. Expression levels of MMP-2 decreased in all fractions, and particularly in the hexane fraction. Furthermore, overexpression of FAS and caspase-3, and increase of cleaved PARP indicates possible apoptosis extrinsic pathway activation. Antiproliferative activity of T. guianensis extract in HNSCC cells lines suggests the possibility of developing an anticancer agent or an additive with synergic activities associated with conventional anticancer therapy.

Structure and Absolute Configuration of Pseudohygrophorones A(12) and B(12), Alkyl Cyclohexenone Derivatives from Hygrophorus abieticola (Basidiomycetes)

Pseudohygrophorones A(12) (1) and B(12) (2), the first naturally occurring alkyl cyclohexenones from a fungal source, and the recently reported hygrophorone B(12) (3) have been isolated from fruiting bodies of the basidiomycete Hygrophorus abieticola Krieglst. ex Gröger & Bresinsky. Their structures were assigned on the basis of extensive one- and two-dimensional NMR spectroscopic analysis as well as ESI-HRMS measurements. The absolute configuration of the three stereogenic centers in the diastereomeric compounds 1 and 2 was established with the aid of (3)JH,H and (4)JH,H coupling constants, NOE interactions, and conformational analysis in conjunction with quantum chemical CD calculations. It was concluded that pseudohygrophorone A(12) (1) is 4S,5S,6S configured, while pseudohygrophorone B(12) (2) was identified as the C-6 epimer of 1, corresponding to the absolute configuration 4S,5S,6R. In addition, the mass spectrometric fragmentation behavior of 1-3 obtained by the higher energy collisional dissociation method allows a clear distinction between the pseudohygrophorones (1 and 2) and hygrophorone B(12) (3). The isolated compounds 1-3 exhibited pronounced activity against phytopathogenic organisms.

Antiproliferative Trihydroxyalkylcyclohexenones from Pleiogynium timoriense

Investigation of a DCM extract of the bark of Pleiogynium timoriense from the former Merck collection of natural product extracts for antiproliferative activity indicated that it was active with an IC50 value of 1.3 μg/mL against the A2780 ovarian cancer cell line. Bioassay-directed fractionation of this extract yielded the three new bioactive trihydroxyalkylcyclohexenones 1-3. Their structures were determined by a combination of spectroscopic and chemical methods. Compounds 1-3 exhibited submicromolar antiproliferative activity against the A2780 human ovarian cancer cell line, with IC50 values of 0.8, 0.7, and 0.8 μM, respectively.

Cardanols, Long Chain Cyclohexenones and Cyclohexenols from Lannea schimperi (Anacardiaceae)

Alkenyl cyclohexenones (1a-d), alkenyl cyclohexenols (2a-c and 3b-d) and cardanols (4a-d) were isolated from the stem bark and root of Lannea schimperi. The alkenyl cyclohexenones (1a and 1d) and cardanols (4a and 4d) have side chains which have not been reported previously, in combination with the core skeletal structures. In addition, compounds 2a-c and 3b-d are all new cyclohexenols. Also isolated were the triterpenes, taraxerone and taraxerol, and sitosterol. The suite of compounds isolated (cyclohexenones and cyclohexenols) make up a nice biosynthetic pathway to the cardanols. The 5-[alkenyl]-4,5-dihydroxycyclohex-2-enone mixture (1a-d) exhibited good in vitro cytotoxicity against the Chinese Hamster Ovarian mammalian cell-line. The compounds were identified mainly from GCMS and NMR spectroscopic techniques.

Amazonian plant natural products: perspectives for discovery of new antimalarial drug leads

Plasmodium falciparum and P. vivax malaria parasites are now resistant, or showing signs of resistance, to most drugs used in therapy. Novel chemical entities that exhibit new mechanisms of antiplasmodial action are needed. New antimalarials that block transmission of Plasmodium spp. from humans to Anopheles mosquito vectors are key to malaria eradication efforts. Although P. vivax causes a considerable number of malaria cases, its importance has for long been neglected. Vivax malaria can cause severe manifestations and death; hence there is a need for P. vivax-directed research. Plants used in traditional medicine, namely Artemisia annua and Cinchona spp. are the sources of the antimalarial natural products artemisinin and quinine, respectively. Based on these compounds, semi-synthetic artemisinin-derivatives and synthetic quinoline antimalarials have been developed and are the most important drugs in the current therapeutic arsenal for combating malaria. In the Amazon region, where P. vivax predominates, there is a local tradition of using plant-derived preparations to treat malaria. Here, we review the current P. falciparum and P. vivax drug-sensitivity assays, focusing on challenges and perspectives of drug discovery for P. vivax, including tests against hypnozoites. We also present the latest findings of our group and others on the antiplasmodial and antimalarial chemical components from Amazonian plants that may be potential drug leads against malaria.

Analysis of additivity and synergism in the anti-plasmodial effect of purified compounds from plant extracts

In the search for antimalarials from ethnobotanical origin, plant extracts are chemically fractionated and biological tests guide the isolation of pure active compounds. To establish the responsibility of isolated active compound(s) to the whole antiplasmodial activity of a crude extract, the literature in this field was scanned and results were analysed quantitatively to find the contribution of the pure compound to the activity of the whole extract. It was found that, generally, the activity of isolated molecules could not account on their own for the activity of the crude extract. It is suggested that future research should take into account the “drugs beside the drug”, looking for those products (otherwise discarded along the fractionation process) able to boost the activity of isolated active compounds.

NMR spectral assignments of two sterols from a soft coral Sinularia brassica

Two new steroids, named 4α,22-dimethyl-Cholest-22-en-3β-ol (1) and 4α-methyl-Cholest-7,22-dien-3β-ol (2), along with two known steroids, were isolated from the soft coral Sinularia brassica. The structures of the new compounds were determined on the basis of extensive spectroscopic data (MS, (1)H and (13)C NMR, (1)H-(1)H COSY, (13)C-(1)H COSY, HMBC and NOESY) analysis.

The evolution of metabolic profiling in parasitology

The uses of metabolic profiling technologies such as mass spectrometry and nuclear magnetic resonance spectroscopy in parasitology have been multi-faceted. Traditional uses of spectroscopic platforms focused on determining the chemical composition of drugs or natural products used for treatment of parasitic infection. A natural progression of the use of these tools led to the generation of chemical profiles of the parasite in in vitro systems, monitoring the response of the parasite to chemotherapeutics, profiling metabolic consequences in the host organism and to deriving host-parasite interactions. With the dawn of the post-genomic era the paradigm in many research areas shifted towards Systems Biology and the integration of biomolecular interactions at the level of the gene, protein and metabolite. Although these technologies have yet to deliver their full potential, metabolic profiling has a key role to play in defining diagnostic or even prognostic metabolic signatures of parasitic infection and in deciphering the molecular mechanisms underpinning the development of parasite-induced pathologies. The strengths and weaknesses of the various spectroscopic technologies and analytical strategies are summarized here with respect to achieving these goals.

Plant-derived antimalarial agents: new leads and efficient phytomedicines. Part II. Non-alkaloidal natural products

Malaria is still the most destructive and dangerous parasitic infection in many tropical and subtropical countries. The burden of this disease is getting worse, mainly due to the increasing resistance of Plasmodium falciparum against the widely available antimalarial drugs. There is an urgent need for new, more affordable and accessible antimalarial agents possessing original modes of action. Natural products have played a dominant role in the discovery of leads for the development of drugs to treat human diseases, and this fact anticipates that new antimalarial leads may certainly emerge from tropical plant sources. This present review covers most of the recently-published non-alkaloidal natural compounds from plants with antiplasmodial and antimalarial properties, belonging to the classes of terpenes, limonoids, flavonoids, chromones, xanthones, anthraquinones, miscellaneous and related compounds, besides the majority of papers describing antiplasmodial crude extracts published in the last five years not reviewed before. In addition, some perspectives and remarks on the development of new drugs and phytomedicines for malaria are succinctly discussed.