Genome Assembly of the Medicinal Plant Voacanga thouarsii.

The Apocynaceae tree Voacanga thouarsii, native to southern Africa and Madagascar, produces monoterpene indole alkaloids (MIA), which are specialized metabolites with a wide range of bioactive properties. Voacanga species mainly accumulates tabersonine in seeds making these species valuable medicinal plants currently used for industrial MIA production. Despite their importance, the MIA biosynthesis in Voacanga species remains poorly studied. Here, we report the first genome assembly and annotation of a Voacanga species. The combined assembly of Oxford Nanopore Technologies long-reads and Illumina short-reads resulted in 3,406 scaffolds with a total length of 1,354.26 Mb and an N50 of 3.04 Mb. A total of 33,300 protein-coding genes were predicted and functionally annotated. These genes were then used to establish gene families and to investigate gene family expansion and contraction across the phylogenetic tree. A transposable element (TE) analysis showed the highest proportion of TE in Voacanga thouarsii compared with all other MIA-producing plants. In a nutshell, this first reference genome of V. thouarsii will thus contribute to strengthen future comparative and evolutionary studies in MIA-producing plants leading to a better understanding of MIA pathway evolution. This will also allow the potential identification of new MIA biosynthetic genes for metabolic engineering purposes.

Voacanga globosa Spirobisindole Alkaloids Exert Antiviral Activity in HIV Latently Infected Cell Lines by Targeting the NF-kB Cascade: In Vitro and In Silico Investigations.

Since the efficiency in the transcription of the HIV genome contributes to the success of viral replication and infectivity, we investigated the downregulating effects of the spirobisindole alkaloids globospiramine (1), deoxyvobtusine (2), and vobtusine lactone (3) from the endemic Philippine medicinal plant, Voacanga globosa, during HIV gene transcription. Alkaloids 1-3 were explored for their inhibitory activity on TNF-α-induced viral replication in two latently HIV-infected cell lines, OM10.1 and J-Lat. The induction of HIV replication from OM10.1 and J-Lat cells elicited by TNF-α was blocked by globospiramine (1) within noncytotoxic concentrations. Furthermore, globospiramine (1) was found to target the NF-ĸB activation cascade in a dose-dependent manner when the transcriptional step at which inhibitory activity is exerted was examined in TNF-α-induced 293 human cells using transient reporter (luciferase) gene expression systems (HIV LTR-luc, ĸB-luc, and mutant ĸB-luc). Interrogation through molecular docking against the NF-ĸB p50/p65 heterodimer and target sites of the subunits comprising the IKK complex revealed high binding affinities of globospiramine (1) against the S281 pocket of the p65 subunit (BE = -9.2 kcal/mol) and the IKKα activation loop (BE = -9.1 kcal/mol). These findings suggest globospiramine (1) as a molecular inspiration to discover new alkaloid-based anti-HIV derivatives.

Bisindole alkaloids from Voacanga grandifolia leaves.

Two new bisindole alkaloids, 12'-O-demethyl-vobtusine-5-lactam and isovobtusine-N-oxide (1 and 2), were isolated from the leaves of Voacanga grandifolia, together with two known bisindole alkaloids. Their structures were elucidated on the basis of 1D and 2D NMR data. 1 and 2 showed potent antimalarial activity against Plasmodium falciparum 3D7 and very low cytotoxic activity against a human cell line, HepG2 cells.

Pharmacokinetics of hERG Channel Blocking Voacangine in Wistar Rats Applying a Validated LC-ESI-MS/MS Method.

Herbal preparations from Voacanga africana are used in West and Central African folk medicine and are also becoming increasingly popular as a legal high in Europe. Recently, the main alkaloid voacangine was found to be a potent human ether-à-go-go-related gene channel blocker in vitro. Blockage of this channel might imply possible cardiotoxicity. Therefore, the aim of this study was to characterise voacangine in vivo to assess its pharmacokinetics and to estimate if further studies to investigate its cardiotoxic risk are required. Male Wistar rats received different doses of voacangine as a pure compound and as a hydro-ethanolic extract of V. africana root bark with a quantified amount of 9.71 % voacangine. For the obtained data, a simultaneous population pharmacokinetics model was successfully developed, comprising a two-compartment model for i. v. dosing and a one-compartmental model with two first-order absorption rates for oral dosing. The absolute bioavailability of voacangine was determined to be 11-13 %. Model analysis showed significant differences in the first absorption rate constant for voacangine administered as a pure compound and voacangine from the extract of V. africana. Taking into account the obtained low bioavailability of voacangine, its cardiotoxic risk might be neglectable in healthy consumers, but may have a serious impact in light of drug/drug interactions and impaired health conditions.

Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity.

In this study, essential oils from Voacanga africana seeds at different extraction stages were investigated. In the chemical composition analysis, 27 compounds representing 86.69-95.03% of the total essential oils were identified and quantified. The main constituents in essential oils were terpenoids, alcohols and fatty acids accounting for 15.03-24.36%, 21.57-34.43% and 33.06-57.37%, respectively. Moreover, the analysis also revealed that essential oils from different extraction stages possessed different chemical compositions. In the antioxidant evaluation, all analysed oils showed similar antioxidant behaviours, and the concentrations of essential oils providing 50% inhibition of DPPH-scavenging activity (IC50) were about 25 mg/mL. In the antimicrobial experiments, essential oils from different extraction stages exhibited different antimicrobial activities. The antimicrobial activity of oils was affected by extraction stages. By controlling extraction stages, it is promising to obtain essential oils with desired antimicrobial activities.

Apoptosis-inducing activity of HPLC fraction from Voacanga globosa (Blanco) Merr. on the human colon carcinoma cell.

Voacanga globosa (Blanco), a plant endemic to the Philippines, is traditionally used especially by indigenous people of Bataan in the treatment of ulcers, wounds and tumorous growths. This study aimed to provide scientific evidence to therapeutic properties by determining cytotoxic and pro-apoptotic activity of HPLC fractions from leaves on HCT116 human colon carcinoma and A549 human lung carcinoma cell lines. Ethanolic extraction was performed on V globosa leaves followed by hexane and ethyl acetate partitioning. Silica gel column chromatography and high performance liquid chromatography (HPLC) produced MP1, MP2 and MP3 fractions. Cytotoxic activity of the fractions was determined through MTT assay against the cancer cell lines HCT116 and A549 and the non-cancer AA8 Chinese hamster ovarian cell line. Pro-apoptotic activities of the most active fractions were further assessed through DAPI staining, TUNEL assay and JC-1 mitochondrial membrane potential assay with HCT116 cells. While the MP1 fraction exerted no significant activity against all cell lines tested, MP2 and MP3 fractions demonstrated high toxicity against HCT116 and A549 cells. The MP3 fraction induced formation of apoptotic bodies, condensed DNA and other morphological changes consistent with apoptosis of HCT116 cells and TUNEL assay showed significant increase in DNA fragmentation over time. In these cells, the MP3 fraction also induced mitochondrial membrane destabilization, which is generally associated with the beginning of apoptosis. Phytochemical analysis demonstrated the presence only of saponins and terpenoids in the MP3 fraction. The results indicate that the MP3 fraction exerts cytotoxic activity on HCT116 cells via induction of apoptosis triggered by loss of mitochondrial membrane potential crucial for cell survival.

Chemistry and biology of the genus Voacanga.

CONTEXT: Herbal remedies have been employed for the treatment and management of various ailments since the beginning of human civilization. Voacanga is an extensive genus of the family Apocynaceae and consists of small trees inhabiting the tropical and subtropical regions of Africa. Voacanga plants have been used in the treatment of leprosy, diarrhea, and generalized edema, convulsions in children as well as to treat cases of orchitis, ectopic testes and gonorrhea. OBJECTIVES: The aim of this review is to present as much information as was established from the available scientific literature. The present review comprises the ethnopharmacological, phytochemical and therapeutic potential of the plant genus Voacanga. METHODS: The present review reports on 111 natural products as found in 44 references compiled from the major databases, viz., Chemical Abstracts, Science Direct, SciFinder, PubMed, Dr. Dukes Phytochemical and Ethnobotany, CIMER, and InteliHealth. RESULTS: An exhaustive survey of the literature revealed that indole alkaoids and steroids constitute the major classes of phytoconstituents of this genus. Pharmacological reports revealed that products derived from this genus have been used for the treatment of cancer, and for CNS, cardiotonic, antituberculosis, acetylcholinesterase (AChE), butyrylcholinesterase, antagonistic, anti-diarrheal activities.

Antimicrobial activity, cytotoxicity, and phytochemical screening of Voacanga globosa (Blanco) Merr. leaf extract (Apocynaceae).

OBJECTIVE: To determine the antibacterial, antifungal, antiprotozoal, cytotoxic, and phytochemical properties of ethanol extracts of leaves of Voacanga globosa (Blanco) Merr. (V. globosa). METHODS: The extracts were tested against bacteria and fungus through disc diffusion assay; against protozoa through growth curve determination, antiprotozoal and cytotoxicity assays. RESULTS: The extract revealed antibacterial activities, inhibiting the growth of Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Micrococcus luteus, and Salmonella typhimurium. Antifungal assay showed that it inhibited Candida albicans. The antiprotozoal assay against Trichomonas vaginalis and Entamoeba histolytica showed that V. globosa can inhibit the parasites, wherein the action can be comparable to metronidazole. With the in situ cell death detection kit, Trichomonas vaginalis and Entamoeba histolytica exposed to V. globosa leaf extract was observed to fluoresce simultaneously in red and yellow signals signifying apoptotic-like changes. Preliminary phytochemical screening revealed the chemical composition of plant extract containing alkaloids, saponins, 2-deoxysugars, and hydrolysable tannins. CONCLUSIONS: Thus, this study provides scientific evidence on the traditional use of V. globosa leaf extract in treating microbial diseases. Further, the leaf extract can possibly be used to produce alternative forms of antimicrobials.

Mycobacterium tuberculosis and cholinesterase inhibitors from Voacanga globosa.

Globospiramine (1), a new spirobisindole alkaloid possessing an Aspidosperma-Aspidosperma skeleton, together with deoxyvobtusine (2), deoxyvobtusine lactone (3), vobtusine lactone (4) and lupeol (5), were isolated and identified from Voacanga globosa through a bioassay-guided purification. The gross structure and absolute stereochemistry of 1 were established by circular dichroism spectroscopy, HR-MS and unambiguous NMR spectroscopic experiments. In addition, a new biogenetic pathway for the formation of the spiro-Aspidosperma-Aspidosperma skeleton is proposed. Alkaloid 1 showed potent antituberculosis activity against Mycobacterium tuberculosis H(37)Rv as evidenced in microplate Alamar blue assay (MIC = 4 µg/mL) and low-oxygen recovery assay (LORA (MIC = 5.2 µg/mL). The bisindole alkaloids also exhibited promising activity against acetylcholinesterase and, especially butyrylcholinesterase, with deoxyvobtusine (2) (IC(50) = 6.2 µM) as the most strongly inhibiting compound. This study extends the variety of alkaloid structural platforms which exhibit antimycobacterial and anticholinesterase activity.

Discovery of indole alkaloids with cannabinoid CB1 receptor antagonistic activity.

Three indole alkaloids, voacamine (1), 3,6-oxidovoacangine (2), and a new alkaloid, 5-hydroxy-3,6-oxidovoacangine (3), isolated from Voacanga africana were found to exhibit potent cannabinoid CB1 receptor antagonistic activity. This is the first example of CB1 antagonists derived from natural alkaloids.

Antimicrobial activity, cytotoxicity, and phytochemical screening of Voacanga globosa (Blanco) Merr. leaf extract (Apocynaceae)

OBJECTIVE@#To determine the antibacterial, antifungal, antiprotozoal, cytotoxic, and phytochemical properties of ethanol extracts of leaves of Voacanga globosa (Blanco) Merr. (V. globosa).@*METHODS@#The extracts were tested against bacteria and fungus through disc diffusion assay; against protozoa through growth curve determination, antiprotozoal and cytotoxicity assays.@*RESULTS@#The extract revealed antibacterial activities, inhibiting the growth of Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Micrococcus luteus, and Salmonella typhimurium. Antifungal assay showed that it inhibited Candida albicans. The antiprotozoal assay against Trichomonas vaginalis and Entamoeba histolytica showed that V. globosa can inhibit the parasites, wherein the action can be comparable to metronidazole. With the in situ cell death detection kit, Trichomonas vaginalis and Entamoeba histolytica exposed to V. globosa leaf extract was observed to fluoresce simultaneously in red and yellow signals signifying apoptotic-like changes. Preliminary phytochemical screening revealed the chemical composition of plant extract containing alkaloids, saponins, 2-deoxysugars, and hydrolysable tannins.@*CONCLUSIONS@#Thus, this study provides scientific evidence on the traditional use of V. globosa leaf extract in treating microbial diseases. Further, the leaf extract can possibly be used to produce alternative forms of antimicrobials.

Antiparasitic activity of alkaloids from plant species of Papua New Guinea and Australia.

New drugs are needed to help overcome the increasing problem of drug resistance in parasites that cause diseases such as malaria and trypanosomiasis. In this study, alkaloid compounds isolated from extracts of the plants Flindersia amboinensis, Stephania zippeliana and Voacanga papuana from Papua New Guinea and Flindersia acuminata from Australia were examined for their antiparasitic activity against Plasmodium falciparum strains and Trypanosoma brucei brucei as well as their cytotoxicity against the mammalian cell lines HEK 293 and HeLa. The most active compound, dimethylisoborreverine (DMIB), showed submicromolar activity, with 50% inhibitory concentration (IC(50)) values between 20 nM and 810 nM both against drug-sensitive and drug-resistant P. falciparum strains, along with moderate selectivity against T. b. brucei and mammalian cells. Stage specificity studies revealed that P. falciparum trophozoite-stage parasites were more susceptible to DMIB than ring- or schizont-stage parasites. DMIB-treated trophozoites showed changes in food vacuole morphology, with an apparent reduction in haemozoin formation that does not appear to be inhibited via the direct binding of haem. These findings suggest a potential for indole alkaloids from Flindersia spp. as new antiparasitic agents.

[Chemical and DNA analyses for the products of a psychoactive plant, Voacanga africana].

Voacanga africana (Apocynaceae) is a small tropical African tree. The root bark and seeds of this tree contain a number of alkaloids, including ibogaine (a hallucinogenic/aphrodisiac compound in bark), tabersonine (a major constituteent of seeds) and other voacanga alkaloids, traditionally used in Africa for religious purposes. Recently, some kinds of products containing this plant (root bark and seeds) have been distributed in the drug market in expectation of its hallucinogenic/aphrodisiac effects. There has been no report that has discussed quantitative analyses of these alkaloids in the products and their botanical origins. In this study, to investigate the trend of such a non-controlled psychotropic plant of abuse, a simultaneous analytical method was developed using LC/MS for the voacanga alkaloids including ibogaine and tabersonine in the commercial products of V. africana. Moreover, the botanical origins of these products were investigated by DNA analyses. As a result of the LC/MS analyses, the products were classified into two chemical types; an ibogaine-type and a tabersonine-type. The samples of the ibogaine-type contain ibogaine (0.05-0.6%) and other voacanga alkaloids; voacamine, voacamidine and voacangine, while those of the tabersonine-type mainly contain tabersonine (0.6-1.6%). The sequence analyses of chloroplast DNA, trnL-F region suggested that most of the products were derived from V. africana or closely related plants. They were classified into four genotypes based on nucleotide sequence of the trnL-F IGS region. The proposed methods of chemical and DNA analyses would be useful for investigating the trend in the distribution of the products of V. africana.