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

Phytochemical Extracts of Dittrichia viscosa (L.) Greuter from Agroecological Systems: Seed Antigerminative Properties and Effectiveness in Counteracting Alternaria Leaf Spot Disease on Baby-Leaf Spinach

Dittrichia viscosa (L.) Greuter subsp. viscosa (Asteraceae) is a perennial species naturally distributed in arid and marginal areas whose agroecological cultivation could be a useful innovation to produce quality biomass to extract phenolic-rich phytochemical blends. Here, biomass-yield trends were profiled at different growth stages under direct cropping, and inflorescences, leaves, and stems were submitted to water extraction and hydrodistillation. Then, four extracts were investigated for their biological activities in invitro and in planta assays. Extracts inhibited cress (Lepidium sativum)- and radish (Raphanus sativus)-seed germination and root elongation. All samples showed dose-dependent antifungal activity in the plate experiments, inhibiting up to 65% of the growth of the fungal pathogen Alternaria alternata, a leaf-spot disease agent of baby spinach (Spinacea oleracea). However, only the extracts from dried green parts and fresh inflorescences at the highest concentration significantly reduced (54%) the extent of Alternaria necrosis on baby spinach. UHPLC-HRMS/MS analysis revealed that the main specialized metabolites of the extracts are caffeoyl quinic acids, methoxylated flavonoids, sesquiterpene compounds such as tomentosin, and dicarboxylic acids, which may explain the observed bioactivity. Plant extracts obtained through sustainable methodology can be effective in biological agricultural applications.

Assessment of antimalarial medicinal plants used in Nigerian ethnomedicine reveals antimalarial potential of Cucurbita pepo leaf extract

Medicinal plants are often used to treat malaria in different parts of Nigeria and exploiting these can unravel new therapeutic leads. This study evaluated the antiplasmodial potential of selected plants used to treat malaria in Nsukka, Enugu state, Nigeria. Leaves of three different plants (Cucurbita pepo, Hibiscus rosa-sinensis and Pennisetum purpureum) were collected for screening and two extracts viz., 70%v/v ethanol and dichloromethane/methanol (1:1 v/v), were prepared for each. An acute toxicity test was done in mice and cytotoxicity was assessed using human hepatoma cell line (HUH). The extracts were screened against chloroquine-sensitive P. falciparum (Pf3D7) in vitro, and chloroquine-resistant P. berghei ANKA in vivo using a 4 day-suppressive test in mice. Cucurbita pepo ethanol extract was further tested for hemolytic effect on human erythrocytes and in established infection in mice. Parameters assessed were post-treatment parasitemia, hematological indices, organ (brain, kidney, liver, and spleen) weights, and survival. The extracts were non-cytotoxic up to a test dose of 100 μg/ml and 2000 mg/kg fed - mice did not show acute or delayed toxicity. Cucurbita pepo ethanol extract (CpE) displayed excellent in vitro antiplasmodial activity with IC₅₀ of 3.05 μg/ml. At an oral dose of 500 mg/kg, mice were observed to display significant (p < 0.01) ∼51% suppression of parasitemia. The extract did not produce any significant hemolytic effect up to a test concentration of 1 mg/ml. In established infection, a dose of 300 mg/kg significantly (p < 0.01) protected mice from anemia caused by low hematocrit. The extract produced significant (p < 0.05) elevation in red blood cells and platelet counts, and an increase in hemoglobin was evident at 100 and 300 mg/kg. Further, CpE in a dose-dependent manner, reversed liver and spleen weight increase seen in untreated, infected mice. These findings show C. pepo as a potential candidate for further studies to identify its bioactive principle(s) and possible mechanism(s) of antimalarial action.

Antiplasmodial activity of Benth. Leaf and bark extracts against infected mice

Ethnopharmacology relevance

Morinda lucida is an ethnopharmacologically important plant that has traditionally been used to treat malaria in the Southwest of Nigeria. The aim of this study is to look into the antiplasmodial properties of different solvent extracts of Morinda lucida bark and leaves.

Materials and methods

The antiplasmodial model, (or curative assay), was tested against Plasmodium berghei NK65, a chloroquine-sensitive Plasmodium berghei strain. In experimental mice, parasitaemia, percentage inhibition, weight changes, and packed cell volume were measured and compared to chloroquine (10 mg kg⁻¹). Standard phytochemical procedures were used to evaluate the extracts' chemo-profile.

Results and Discussion

Phytochemical analysis of the extracts revealed the presence of tannins, alkaloids, steroids, saponins, phenols, and alkaloids, among other metabolites. The highest quantities of total phenolic, total tannins, and total flavonoid content were found in 50% ethanolic extracts. There was significant decrease in the body weight of the mice after inoculation, however, after administration of crude extracts, an increase in weight was observed. A negative variation (-3.00 g) was observed in group without treatment. The ethanolic crude extracts (200 and 400 mg/kg) significantly increased the packed cell volume compared to other extracts. CQ treated experimental mice showed 100% inhibition with activity greater than extracts treated groups. The lowest inhibitory effect was observed in 200 mg/kg ethanolic bark extract treated group with activity of 72.16%. The antiplasmodial activities exhibited by these extracts could be linked to the chemical constituents investigated.

Conclusion

The findings of this study suggest the use of M. lucida leaves and bark as a medicinal agent for malaria treatment and as a potential source of effective antimalarial templates. Further research is needed to determine the safety and toxicological profile of these extracts in vivo.

Neuroimmunomodulatory Properties of Flavonoids and Derivates: A Potential Action as Adjuvants for the Treatment of Glioblastoma

Glioblastomas (GBMs) are tumors that have a high ability to migrate, invade and proliferate in the healthy tissue, what greatly impairs their treatment. These characteristics are associated with the complex microenvironment, formed by the perivascular niche, which is also composed of several stromal cells including astrocytes, microglia, fibroblasts, pericytes and endothelial cells, supporting tumor progression. Further microglia and macrophages associated with GBMs infiltrate the tumor. These innate immune cells are meant to participate in tumor surveillance and eradication, but they become compromised by GBM cells and exploited in the process. In this review we discuss the context of the GBM microenvironment together with the actions of flavonoids, which have attracted scientific attention due to their pharmacological properties as possible anti-tumor agents. Flavonoids act on a variety of signaling pathways, counteracting the invasion process. Luteolin and rutin inhibit NFκB activation, reducing IL-6 production. Fisetin promotes tumor apoptosis, while inhibiting ADAM expression, reducing invasion. Naringenin reduces tumor invasion by down-regulating metalloproteinases expression. Apigenin and rutin induce apoptosis in C6 cells increasing TNFα, while decreasing IL-10 production, denoting a shift from the immunosuppressive Th2 to the Th1 profile. Overall, flavonoids should be further exploited for glioma therapy.

Antibacterial activity of Mallotus japonicus (L.F.) Müller Argoviensis on growth of Aeromonas hydrophila, A. salmonicida, Edwardsiella tarda and Vibrio anguillarum

AIMS

The present study evaluated the antimicrobial activities of the medicinal plant Mallotus japonicus against the fish pathogenic bacteria, Aeromonas hydrophila, Aeromonas salmonicida, Edwardisella tarda and Vibrio anguillarum, and also describes the antimicrobial activities of the major and minor active compounds present within the plant extract. The synergistic effects by way of combination of these compounds were also evaluated and described. Chemical constituents of the plant extracts were analysed using the liquid chromatography-mass spectrometry (LC-MS) and described.

METHODS AND RESULTS

The diethyl ether-extract of the plant elicited the strongest antibacterial activity against the challenged bacterial species, followed by ethanol- and methanol-extracts. The major active compound of the extracts, bergenin, demonstrated no antibacterial activity, but other compounds in the extracts did.

CONCLUSION

Mallotus japonicus could be used as a prophylaxis to treat bacterial disease infections of fishes and its diethyl ether-extract has the potential of an alternative to antibiotic treatment in aquaculture.

SIGNIFICANCE AND IMPACT OF THE STUDY

Mallotus japonicus diethyl ether-extract has the potential of an alternative to antibiotic treatment in aquaculture.

Epilobium angustifolium L. Extracts as Valuable Ingredients in Cosmetic and Dermatological Products

Epilobium angustifolium L. is a popular and well-known medicinal plant. In this study, an attempt to evaluate the possibility of using this plant in preparations for the care and treatment of skin diseases was made. The antioxidant, antiaging and anti-inflammatory properties of ethanolic extracts from Epilobium angustifolium (FEE) were assessed. Qualitative and quantitative evaluation of extracts chemically composition was performed by gas chromatography with mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). The total polyphenol content (TPC) of biologically active compounds, such as the total content of polyphenols (TPC), flavonoids (TFC), and assimilation pigments, as well as selected phenolic acids, was assessed. FEE was evaluated for their anti-inflammatory and antiaging properties, achieving 68% inhibition of lipoxygenase activity, 60% of collagenase and 49% of elastase. FEE also showed high antioxidant activity, reaching to 87% of free radical scavenging using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 59% using 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). Additionally, in vitro penetration studies were performed using two vehicles, i.e., a hydrogel and an emulsion containing FEE. These studies showed that the active ingredients contained in FEE penetrate through human skin and accumulate in it. The obtained results indicate that E. angustifolium may be an interesting plant material to be applied as a component of cosmetic and dermatological preparations with antiaging and anti-inflammatory properties.

Andrographis paniculata (Burm. F.) Wall. Ex Nees, Andrographolide, and Andrographolide Analogues as SARS-CoV-2 Antivirals? A Rapid Review

Drug repurposing is commonly employed in the search for potential therapeutic agents. Andrographis paniculata, a medicinal plant commonly used for symptomatic relief of the common cold, and its phytoconstituent andrographolide, have been repeatedly identified as potential antivirals against SARS-CoV-2. In light of new evidence emerging since the onset of the COVID-19 pandemic, this rapid review was conducted to identify and evaluate the current SARS-CoV-2 antiviral evidence for A. paniculata, andrographolide, and andrographolide analogs. A systematic search and screen strategy of electronic databases and gray literature was undertaken to identify relevant primary articles. One target-based in vitro study reported the 3CLpro inhibitory activity of andrographolide as being no better than disulfiram. Another Vero cell-based study reported potential SARS-CoV-2 inhibitory activity for both andrographolide and A. paniculata extract. Eleven in silico studies predicted the binding of andrographolide and its analogs to several key antiviral targets of SARS-CoV-2 including the spike protein-ACE-2 receptor complex, spike protein, ACE-2 receptor, RdRp, 3CLpro, PLpro, and N-protein RNA-binding domain. In conclusion, in silico and in vitro studies collectively suggest multi-pathway targeting SARS-CoV-2 antiviral properties of andrographolide and its analogs, but in vivo data are needed to support these predictions.

Bioassay-guided isolation of vilasinin-type limonoids and phenyl alkene from the leaves of Trichilia gilgiana and their antiplasmodial activities

Bioassay-guided fractionation of the CH₂Cl₂-MeOH (1:1) leaves extract of Trichilia gilgiana, yielded two new vilasinin-type limonoids named gilgianin A (1) and gilgianin B (2), one new phenyl alkene derivative designated as gilgialkene A (3), along with six known compounds: rubescin H (4), TS3 (5), trichirubine A (6), sitosteryl-6'-O-undecanoate-β-D-glucoside (7), scopoletin (8), and octadecane-2-one (9). Their structures were elucidated based on spectroscopic analysis and comparison with literature data. Compounds 5 and 6 exhibited the highest antiplasmodial activity with IC₅₀ values of 1.14 and 1.32 μM respectively. Moreover, compound 5 was very cytotoxic with CC₅₀ value of 0.88 µM, compared to compound 6, which was not cytotoxic (CC₅₀ > 10 µg/mL). Compounds 1 (IC₅₀ = 9.84 µM), 2 (IC₅₀ = 11.04 µM) and 4 (IC₅₀ = 10.71 µM) presented good antiplasmodial activity while also exhibiting significant cytotoxicity, with CC₅₀ values ranging from of 14.45 to 29.7 µM.

Antimalarial Activity of Nigella sativa L. Seed Extracts and Selection of Resistance in Plasmodium berghei ANKA in a Mouse Model

Background

Chemotherapy plays a crucial role in malaria control. However, the main obstacle to treatment has been the rise of parasite resistance to most antimalarial drugs. Artemisinin-based combination therapies (ACTs) remain the most effective antimalarial medicines available today. However, malaria parasite tolerance to ACTs is now increasingly prevalent especially in Southeast Asia presenting the danger of the spread of ACTs resistance to other parts of the world. Consequently, this creates the need for alternative effective antimalarials. Therefore, this study sought out to determine antimalarial potential, safety, and resistance development of the extracts in a mouse model.

Method

Methanolic and ethyl acetate extracts were obtained by solvent extraction. The extracts were assayed for acute toxicity in vivo. Additionally, the two extracts were evaluated for antimalarial activity in vivo against Plasmodium berghei ANKA strain by the 4-day suppressive test at 500, 250, and 125 mg/kg/day. Packed cell volume was evaluated to determine anemia manifestation. Finally, continuous drug pressure experiment at 500 mg/kg and DNA amplification via PCR were conducted. The amplicons underwent through Sanger sequencing.

Results

There was no toxicity realized in the animals at 2000 mg/kg. Importantly, high parasitemia suppression of 75.52% and 75.30% using a dose of 500 mg/kg of methanolic and ethyl acetate extracts, respectively, was noted. The extracts were able to reverse packed cell volume reduction. Nigella sativa-resistant phenotype was selected as delayed parasite clearance. However, there was no change in the nucleotide sequences of PbMDR1 and PbCRT genes.

Conclusion

The results provide room for future exploitation of the plant as an antimalarial.

Bioactive Potential of Extracts of Labrenzia aggregata Strain USBA 371, a Halophilic Bacterium Isolated from a Terrestrial Source

Previous studies revealed the potential of Labrenzia aggregata USBA 371 to produce cytotoxic metabolites. This study explores its metabolic diversity and compounds involved in its cytotoxic activity. Extracts from the extracellular fraction of strain USBA 371 showed high levels of cytotoxic activity associated with the production of diketopiperazines (DKPs). We purified two compounds and a mixture of two other compounds from this fraction. Their structures were characterized by 1D and 2D nuclear magnetic resonance (NMR). The purified compounds were evaluated for additional cytotoxic activities. Compound 1 (cyclo (l-Pro-l-Tyr)) showed cytotoxicity to the following cancer cell lines: breast cancer 4T1 (IC₅₀ 57.09 ± 2.11 µM), 4T1H17 (IC₅₀ 40.38 ± 1.94), MCF-7 (IC₅₀ 87.74 ± 2.32 µM), murine melanoma B16 (IC₅₀ 80.87 ± 3.67), human uterus sarcoma MES-SA/Dx5 P-pg (−) (IC₅₀ 291.32 ± 5.64) and MES-SA/Dx5 P-pg (+) (IC₅₀ 225.28 ± 1.23), and murine colon MCA 38 (IC₅₀ 29.85 ± 1.55). In order to elucidate the biosynthetic route of the production of DKPs and other secondary metabolites, we sequenced the genome of L. aggregata USBA 371. We found no evidence for biosynthetic pathways associated with cyclodipeptide synthases (CDPSs) or non-ribosomal peptides (NRPS), but based on proteogenomic analysis we suggest that they are produced by proteolytic enzymes. This is the first report in which the cytotoxic effect of cyclo (l-Pro-l-Tyr) produced by an organism of the genus Labrenzia has been evaluated against several cancer cell lines.

Ethnopharmacology-aided antiplasmodial evaluation of six selected plants used for malaria treatment in Nigeria

ETHNOPHARMACOLOGICAL RELEVANCE

Sub - Saharan Africa has a high malaria burden and Nigeria accounts for majority of malaria cases worldwide. The aim of this study was to evaluate selected plants extracts used against malaria in Nigeria for antiplasmodial activity.

MATERIALS AND METHODS

An ethnomedicinal based - approach by literature survey was used to identify plants used in the study. The parts of the plant used were collected and extracted with 70% v/v ethanol; a portion of each extract was used to prepare successive solvent and residual fractions. Chloroquine-sensitive (3D7) P. falciparum strain and human embryonic kidney cells (HEK293) were used for antiplasmodial and cytotoxicity screening respectively. Hemolysis assay was also carried out on red blood cells (RBCs). Test for in vivo efficacy of an active extract was conducted in a mouse model of established P. berghei ANKA-infection.

RESULTS

A total of six plants; Andropogon schirensis, Celtis durandii, Chasmanthera dependens, Daniellia ogea, Icacina trichantha and Triumfetta cordifolia were selected and screened. Triumfetta cordifolia leaf extract was observed to display moderate in vitro antiplasmodial activity (IC₅₀ = 48.09 μg/ml) and was non-toxic to HEK293 cells and erythrocytes. At a dose of 400 mg/kg, T. cordifolia significantly (p<0.001) suppressed parasitemia, significantly (p<0.001) inhibited RBC depletion and prolonged survival in infected mice.

CONCLUSIONS

T. cordifolia ethanol extract possesses antiplasmodial efficacy and this is the first report of its kind on the plant. It is a potential candidate for further studies to identify its mechanism of action.

Isolation of the Tephrosia vogelii extract and rotenoids and their toxicity in the RTgill-W1 trout cell line and in zebrafish embryos

This study focused on identifying the rotenoids from the Tephrosia vogelli plant (fish-poison-bean), investigating the toxic potency of a crude T. vogelii extract and individual rotenoids (tephrosin, deguelin and rotenone) in vitro and in vivo and assessing the mode of action. A trout (Onychorynhis mykiss) gill epithelial cell line (RTgill-W1) was used to determine the cytotoxicity of rotenoids and effects on cell metabolism. Zebrafish (Danio rerio) aged from 3 h post fertilization (hpf) to 72 hpf were used for testing the developmental toxicity. The crude T. vogelii plant extract significantly decreased the cellular metabolic activity and was cytotoxic at lower concentrations (5 and 10 nM, respectively), while tephrosin, deguelin and rotenone showed these effects at concentrations ≥ 50 nM. The crude T. Vogelli extract had the highest toxic potency and induced adverse health effects in zebrafish including deformities and mortality at the lowest concentration (5 nM) compared to rotenone (10 nM) and deguelin and tephrosin (50 nM). These results indicate that the crude T. Vogelii extracts are highly potent and the bioactivity of these extracts warrant further investigation for their potential use to treat parasites in human and veterinary medicine and as a natural alternative to pesticides.

Searching Synergistic Dose Combinations for Anticancer Drugs

Recent development has enabled synergistic drugs in treating a wide range of cancers. Being highly context-dependent, however, identification of successful ones often requires screening of combinational dose on different testing platforms in order to gain the best anticancer effects. To facilitate the development of effective computational models, we reviewed the latest strategy in searching optimal dose combination from three perspectives: (1) mainly experimental-based approach; (2) Computational-guided experimental approach; and (3) mainly computational-based approach. In addition to the introduction of each strategy, critical discussion of their advantages and disadvantages were also included, with a strong focus on the current applications and future improvements.

In vivo anti-malarial activity and toxicity studies of triterpenic esters isolated form Keetia leucantha and crude extracts

BACKGROUND

Considering the need for new anti-malarial drugs, further investigations on Keetia leucantha (Rubiaceae), an in vitro antiplasmodial plant traditionally used to treat malaria, were carried out. This paper aimed to assess the in vivo anti-malarial efficacy of K. leucantha triterpenic esters previously identified as the most in vitro active components against Plasmodium falciparum and their potential toxicity as well as those of anti-malarial extracts.

RESULTS

These eight triterpenic esters and the major antiplasmodial triterpenic acids, ursolic and oleanolic acids, were quantified in the twigs dichloromethane extract by validated HPLC-UV methods. They account for about 19% of this extract (16.9% for acids and 1.8% for esters). These compounds were also identified in trace in the twigs decoction by HPLC-HRMS. Results also showed that extracts and esters did not produce any haemolysis, and were devoid of any acute toxicity at a total cumulative dose of 800 and 150 mg/kg respectively. Moreover, esters given intraperitoneally at 50 mg/kg/day to Plasmodium berghei-infected mice showed a very significant (p < 0.01) parasitaemia inhibition (27.8 ± 5.4%) on day 4 post-infection compared to vehicle-treated mice.

CONCLUSIONS

These results bring out new information on the safety of K. leucantha use and on the identification of anti-malarial compounds from its dichloromethane extract. Its activity can be explained by the presence of triterpenic acids and esters which in vivo activity and safety were demonstrated for the first time.

Ethnopharmacological appraisal of culturally important medicinal plants and polyherbal formulas used against communicable diseases in Rodrigues Island

ETHNOPHARMACOLOGICAL RELEVANCE

The tropical island of Rodrigues is one of three islands that constitute the Mascarene archipelago in the Indian Ocean. Currently considered as a biodiversity hotspot, the island has also a resilient history in the use of traditional medicine. However, there has been no ethnopharmacological study to document quantitatively such traditional practice against communicable diseases (CD), which currently accounts for 6.61% annual death and 30.7% attendances in public hospitals. The aim of the present study was to collect, analyse, and document traditionally used medicinal plants (MP) and polyherbal formulas from key informants and traditional medicine practitioners (TMP) in Rodrigues to treat and/or manage common CD.

MATERIALS AND METHODS

Data was collected via face-to-face interviews with MP users (n=113) and TMP (n=9) from 17 key sites. Seven quantitative ethnopharmacological indices, namely family use value (FUV), use value (UV), informant agreement ratio (IAR), relative frequency of citation (RFC), fidelity level (FL), relative importance (RI), and ethnobotanicity index (EI) were calculated.

RESULTS

Ninety-seven plants belonging to 49 families were recorded to be in common use as monotherapy (80 plants) and/or as part of polyherbal preparation (23 plants) for the treatment and/or management of 16 different CD. Thirteen MPs were found to have a maximum FL of 100% for CD. The highest IAR (0.98) was observed for diseases of the eye and adnexa and skin and subcutaneous tissue. The highest FUV was for Arecaceae. Ayapana triplinervis (Vahl) R.M. king et H.Rob. scored the highest UV (UV=2.72). Seven endemic medicinal plants have been recorded to be employed in cultural rituals for the management of common CDs, whereas 14 polyherbal preparations were used to treat and/or manage 6 different types of CDs. Side effects were also reported following use of some these medicinal plants.

CONCLUSION

Given the dearth of updated information on traditional medicine from Rodrigues, this work has provided an opportunity to establish valuable primary information on the different MP used by the local people. Further research is needed to probe into the possible active constituents that could open new perspectives for further pharmacological research and hence be the basis of an evidence-based investigation to discover new drugs.

In vitro and ex vivo activity of an Azadirachta indica A.Juss. seed kernel extract on early sporogonic development of Plasmodium in comparison with azadirachtin A, its most abundant constituent

BACKGROUND

NeemAzal^® (NA) is a quantified extract from seed kernels of neem, Azadirachta indica A.Juss. (Meliaceae), with a wide spectrum of biological properties, classically ascribed to its limonoid content. NA contains several azadirachtins (A to L), azadirachtin A (AzaA) being its main constituent. AzaA has been shown to inhibit microgamete formation of the rodent malaria parasite Plasmodium berghei, and NA was found to completely inhibit the transmission of Plasmodium berghei to Anopheles stephensi mosquitoes when administered to gametocytemic mice at a corresponding AzaA dose of 50mg/kg before exposure to mosquitoes.

PURPOSE

The present study was aimed at i) assessing the pharmacodynamics and duration of action of NA and AzaA against P. berghei exflagellation in systemic circulation in mice and ii) elucidating the transmission blocking activity (TBA) of the main NA constituents.

STUDY DESIGN

The NA and AzaA pharmacodynamics on exflagellation were assessed through ex vivo exflagellation assays, while TBA of NA constituents was evaluated through in vitro ookinete development assay.

METHODS

Pharmacodynamics experiments: Peripheral blood from P. berghei infected BALB/c mice with circulating mature gametocytes, were treated i.p. with 50mg/kg and 100mg/kg pure AzaA and with NeemAzal^® (Trifolio-M GmbH) at the corresponding AzaA concentrations. The effect magnitude and duration of action of compounds was estimated by counting exflagellation centers, formed by microgametocytes in process of releasing flagellated gametes, at various time points after treatment in ex vivo exflagellation tests. Ookinete Development Assay: The direct effects of NeemAzal^® and AzaA on ookinete development were measured by fluorescence microscopy after incubation of gametocytemic blood with various concentrations of test substances in microplates for 24h.

RESULTS

The exflagellation tests revealed an half-life of NA anti-plasmodial compounds of up to 7h at a NA dose corresponding to 100mg/kg equivalent dose of AzaA. The ookinete development assay showed an increased activity of NA against early sporogonic stages compared to that of AzaA. The IC₅₀ value determined for NA was 6.8µg/ml (CI₉₅: 5.95-7.86), about half of the AzaA IC₅₀ (12.4µg/ml; CI₉₅: 11.0-14.04).

CONCLUSION

The stronger activity of NA, when compared to AzaA, could not be explained by an additive or synergistic effect by other azadirachtins (B, D and I) present in NA. In fact, the addition of these compounds at 50µM concentration to AzaA did not evidence any decrease of the IC₅₀ against early sporogonic stages to that obtained with AzaA alone. It is likely that other non-limonoid compounds present in NA may contribute to AzaA activity and enhanced pharmacodynamics against exflagellation both in vitro and in vivo.

Anti-Inflammatory Activity of Natural Products

This article presents highlights of the published literature regarding the anti-inflammatory activities of natural products. Many review articles were published in this regard, however, most of them have presented this important issue from a regional, limited perspective. This paper summarizes the vast range of review and research articles that have reported on the anti-inflammatory effects of extracts and/or pure compounds derived from natural products. Moreover, this review pinpoints some interesting traditionally used medicinal plants that were not investigated yet.

Wayanin and guaijaverin, two active metabolites found in a Psidium acutangulum Mart. ex DC (syn. P. persoonii McVaugh) (Myrtaceae) antimalarial decoction from the Wayana Amerindians

ETHNOPHARMACOLOGICAL RELEVANCE

Psidium acutangulum Mart. ex DC is a small tree used by the Wayana Amerindians from the Upper-Maroni in French Guiana for the treatment of malaria.

AIM OF THE STUDY

In a previous study, we highlighted the in vitro antiplasmodial, antioxidant and anti-inflammatory potential of the traditional decoction of P. acutangulum aerial parts. Our goal was then to investigate on the origin of the biological activity of the traditional remedy, and eventually characterize active constituents.

MATERIALS AND METHODS

Liquid-liquid extractions were performed on the decoction, and the antiplasmodial activity evaluated against chloroquine-resistant FcB1 ([(3)H]-hypoxanthine bioassay) and 7G8 (pLDH bioassay) P. falciparum strains, and on a chloroquine sensitive NF54 ([(3)H]-hypoxanthine bioassay) P. falciparum strain. The ethyl acetate fraction (D) was active and underwent bioguided fractionation. All the isolated compounds were tested on P. falciparum FcB1 strain. In vitro anti-inflammatory activity (IL-1β, IL-6, IL-8, TNFα) of the ethyl acetate fraction and of an anti-Plasmodium active compound, was concurrently assessed on LPS-stimulated human PBMC and NO secretion inhibition was measured on LPS stimulated RAW murine macrophages. Cytotoxicity of the fractions and pure compounds was measured on VERO cells, L6 mammalian cells, PBMCs, and RAW cells.

RESULTS

Fractionation of the ethyl acetate soluble fraction (IC50 ranging from 3.4 to <1µg/mL depending on the parasite strain) led to the isolation of six pure compounds: catechin and five glycosylated quercetin derivatives. These compounds have never been isolated from this plant species. Two of these compounds (wayanin and guaijaverin) were found to be moderately active against P. falciparum FcB1 in vitro (IC50 5.5 and 6.9µM respectively). We proposed the name wayanin during public meetings organized in June 2015 in the Upper-Maroni villages, in homage to the medicinal knowledge of the Wayana population. At 50µg/mL, the ethyl acetate fraction (D) significantly inhibited IL-1β secretion (-46%) and NO production (-21%), as previously observed for the decoction. The effects of D and guiajaverin (4) on the secretion of other cytokines or NO production were not significant.

CONCLUSIONS

The confirmed antiplasmodial activity of the ethyl acetate soluble fraction of the decoction and of the isolated compounds support the previous results obtained on the P. acutangulum decoction. The antiplasmodial activity might be due to a mixture of moderately active non-toxic flavonoids. The anti-inflammatory activities were less marked for ethyl acetate fraction (D) than for the decoction.

Activity of Medicinal Plant Extracts on Multiplication of Mycobacterium tuberculosis under Reduced Oxygen Conditions Using Intracellular and Axenic Assays

Aim. Test the activity of selected medicinal plant extracts on multiplication of Mycobacterium tuberculosis under reduced oxygen concentration which represents nonreplicating conditions. Material and Methods. Acetone, ethanol and aqueous extracts of the plants Acorus calamus L. (rhizome), Ocimum sanctum L. (leaf), Piper nigrum L. (seed), and Pueraria tuberosa DC. (tuber) were tested on Mycobacterium tuberculosis H37Rv intracellularly using an epithelial cell (A549) infection model. The extracts found to be active intracellularly were further studied axenically under reducing oxygen concentrations. Results and Conclusions. Intracellular multiplication was inhibited ≥60% by five of the twelve extracts. Amongst these 5 extracts, in axenic culture, P. nigrum (acetone) was active under aerobic, microaerophilic, and anaerobic conditions indicating presence of multiple components acting at different levels and P. tuberosa (aqueous) showed bactericidal activity under microaerophilic and anaerobic conditions implying the influence of anaerobiosis on its efficacy. P. nigrum (aqueous) and A. calamus (aqueous and ethanol) extracts were not active under axenic conditions but only inhibited intracellular growth of Mycobacterium tuberculosis, suggesting activation of host defense mechanisms to mediate bacterial killing rather than direct bactericidal activity.

Search for Antiprotozoal Activity in Herbal Medicinal Preparations; New Natural Leads against Neglected Tropical Diseases

Sleeping sickness, Chagas disease, Leishmaniasis, and Malaria are infectious diseases caused by unicellular eukaryotic parasites (“protozoans”). The three first mentioned are classified as Neglected Tropical Diseases (NTDs) by the World Health Organization and together threaten more than one billion lives worldwide. Due to the lack of research interest and the high increase of resistance against the existing treatments, the search for effective and safe new therapies is urgently required. In view of the large tradition of natural products as sources against infectious diseases [1,2], the aim of the present study is to investigate the potential of legally approved and marketed herbal medicinal products (HMPs) as antiprotozoal agents. Fifty-eight extracts from 53 HMPs on the German market were tested by a Multiple-Target-Screening (MTS) against parasites of the genera Leishmania, Trypanosoma, and Plasmodium. Sixteen HMPs showed in vitro activity against at least one of the pathogens (IC₅₀ < 10 µg/mL). Six extracts from preparations of Salvia, Valeriana, Hypericum, Silybum, Arnica, and Curcuma exhibited high activity (IC₅₀ < 2.5 µg/mL). They were analytically characterized by UHPLC/ESI-QqTOF-MSMS and the activity-guided fractionation of the extracts with the aim to isolate and identify the active compounds is in progress.

Anti-inflammatory, antioxidant and anti-acetylcholinesterase activities of Bouvardia ternifolia: potential implications in Alzheimer's disease

Bouvardia ternifolia has been used medicinally to treat inflammation. In the present study, we investigate the anti-Alzheimer's potential effect of the hydroalcoholic extract of B. ternifolia through evaluation of anti-inflammatory and antioxidant activities, quantification of the percentage inhibition of acetylcholinesterase activity, protection effect against β-amyloid fibrillar-induce neurotoxicity, and the identification of the main constituents. Our results show that B. ternifolia extract and ethyl acetate fraction induced anti-inflammatory effects by reducing inflammation by >70 %, while antioxidant test revealed significant IC50 values for flavonoid content fraction (30.67 ± 2.09 μg/ml) and ethyl acetate fraction (42.66 ± 0.93 μg/ml). The maximum inhibition of acetylcholinesterase was exhibited by scopoletin content fraction (38.43 ± 3.94 %), while ethyl acetate fraction exerted neuroprotective effect against β-amyloid peptide (83.97 ± 5.03 %). Phytochemical analysis, showed the presence of 3-O-quercetin glucopyranoside (415 mg/g), rutin (229.9 mg/g), ursolic and oleanolic acid (54 and 20.8 mg/g respectively), 3-O-quercetin rhamnopyranoside (12.8 mg/g), chlorogenic acid (9.5 mg/g), and scopoletin (1.38 mg/g). Our findings support the use of B. ternifolia since the extract induced significant neuroprotection against β-amyloid peptide, anti-inflammatory, antioxidant and anti-acetylcholinesterase effects that could be attributed to its contents of polyphenols, coumarins, and triterpenes, and encourage further studies for development of this extract as therapeutic agent in treatment of Alzheimer's disease.

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.

Anti-inflammatory activity of Mitraphylline isolated from Uncaria tomentosa bark

ETHNOPHARMACOLOGICAL RELEVANCE

Uncaria tomentosa (Willd. ex Roem. & Schult.) DC. (Rubiaceae) is widely used by populations living in South America to treat many ailments associated with inflammatory disorders. Mitraphylline was shown to be the major pentacyclic oxindolic alkaloid present in the bark chloroformic extract of this plant. Its activity against cytokines involved in inflammation process was tested in a murine model in vivo.

MATERIALS AND METHODS

Mice received mitraphylline once a day for 3 days at 30 mg/kg/day by oral route. Then, they were subjected to bacterial lipopolysaccharide (LPS) endotoxin (15 mg/kg) and the LPS-induced production of 16 different cytokines was determined by Elisa multiplex. Control group received dexamethasone orally at 2mg/kg/day. Toxicity on K565 cells and murine peritoneal macrophages, in vitro, at doses up to 100 μM was monitored by XTT-colorimetric assay.

RESULTS AND CONCLUSIONS

For the first time mitraphylline was tested in vivo against a large range of cytokines that play a crucial role in inflammation. Mitraphylline inhibited around 50% of the release of interleukins 1α, 1β, 17, and TNF-α. This activity was similar to dexamethasone. It also reduced almost 40% of the production of interleukin 4 (IL-4) while the corticoid did not. Lastly it did not show any toxicity on K565 cells nor murine macrophages at doses up to 100 μM.

Anti-plasmodial activity of Dicoma tomentosa (Asteraceae) and identification of urospermal A-15-O-acetate as the main active compound

Background

Natural products could play an important role in the challenge to discover new anti-malarial drugs. In a previous study, Dicoma tomentosa (Asteraceae) was selected for its promising anti-plasmodial activity after a preliminary screening of several plants traditionally used in Burkina Faso to treat malaria. The aim of the present study was to further investigate the anti-plasmodial properties of this plant and to isolate the active anti-plasmodial compounds.

Methods

Eight crude extracts obtained from D. tomentosa whole plant were tested in vitro against two Plasmodium falciparum strains (3D7 and W2) using the p-LDH assay (colorimetric method). The Peters’ four-days suppressive test model (Plasmodium berghei-infected mice) was used to evaluate the in vivo anti-plasmodial activity. An in vitro bioguided fractionation was undertaken on a dichloromethane extract, using preparative HPLC and TLC techniques. The identity of the pure compound was assessed using UV, MS and NMR spectroscopic analysis. In vitro cytotoxicity against WI38 human fibroblasts (WST-1 assay) and haemolytic activity were also evaluated for extracts and pure compounds in order to check selectivity.

Results

The best in vitro anti-plasmodial results were obtained with the dichloromethane, diethylether, ethylacetate and methanol extracts, which exhibited a high activity (IC₅₀ ≤ 5 μg/ml). Hot water and hydroethanolic extracts also showed a good activity (IC₅₀ ≤ 15 μg/ml), which confirmed the traditional use and the promising anti-malarial potential of the plant. The activity was also confirmed in vivo for all tested extracts. However, most of the active extracts also exhibited cytotoxic activity, but no extract was found to display any haemolytic activity. The bioguided fractionation process allowed to isolate and identify a sesquiterpene lactone (urospermal A-15-O-acetate) as the major anti-plasmodial compound of the plant (IC₅₀ < 1 μg/ml against both 3D7 and W2 strains). This was also found to be the main cytotoxic compound (SI = 3.3). While this melampolide has already been described in the plant, this paper is the first report on the biological properties of this compound.

Conclusions

The present study highlighted the very promising anti-plasmodial activity of D. tomentosa and enabled to identify its main active compound, urospermal A-15-O-acetate. The high anti-plasmodial activity of this compound merits further study about its anti-plasmodial mechanism of action. The active extracts of D. tomentosa, as well as urospermal A 15-O-acetate, displayed only a moderate selectivity, and further studies are needed to assess the safety of the use of the plant by the local population.

New findings on Simalikalactone D, an antimalarial compound from Quassia amara L. (Simaroubaceae)

Quassia amara L. (Simaroubaceae) is a species widely used as tonic and is claimed to be an efficient antimalarial all over the Northern part of the Amazon basin. Quassinoid compound Simalikalactone D (SkD) has been shown to be one of the molecules responsible for the antiplasmodial activity of a watery preparation made out of juvenile fresh leaves of this plant. Because of its strong antimalarial activity, we decided to have a further insight of SkD pharmacological properties, alone or in association with classical antimalarials. At concentrations of up to 200μM, we showed herein that SkD did not exert any apoptotic or necrotic activities in vitro on lymphoblastic cells. However, an antiproliferative effect was evident at concentrations higher than 45nM. SkD was inefficient at inhibiting heme biomineralization and the new permeability pathways induced by the parasite in the host erythrocyte membrane. With respect to Plasmodium falciparum erythrocytic stages, SkD was almost inactive on earlier and later parasite stages, but potently active at the 30th h of parasite cycle when DNA replicates in mature trophozoites. In vitro combination studies with conventional antimalarial drugs showed that SkD synergizes with atovaquone (ATO). The activity of ATO on the Plasmodium mitochondrial membrane potential was enhanced by SkD, which on its own had a poor effect on this cellular parameter.