Bioassay-guided isolation and structure elucidation of cytotoxic stilbenes and flavonols from the leaves of Macaranga barteri.

Bioassay-guided fractionation of the leaves of Macaranga barteri collected from Nigeria led to the isolation of three previously undescribed cytotoxic stilbenes, macabartebenes A-C (1-3), together with six known compounds including prenylated stilbenes: vedelianin (4), schweinfurthin G (5), and mappain (7), prenylated flavonols: 8-prenylkaempferol (6), and broussoflavonol F (8), and the geranylated flavonol, isomacarangin (9). The cytotoxicity of the compounds was evaluated against four human cancer cell lines, with vinblastine as the positive control and DMSO vehicle as the negative control. Vedelianin (IC50 = 0.32-0.54 µM) displayed the greatest antiproliferative activity across the panel of cancer cell lines amongst the compounds, while macabartebene A (IC50 = 0.60-0.79 µM) was the most potent of the previously unreported compounds. The compounds displayed varying selectivity towards the cancer cell lines compared to the normal human prostate cell line. The findings of this study revealed that M. barteri leaves contain several cytotoxic compounds.

Resveratrol derivatives from Commiphora africana (A. Rich.) Endl. display cytotoxicity and selectivity against several human cancer cell lines.

Commiphora africana (A. Rich.) Endl. (Burseraceae) is a medicinal plant widely used in Nigerian ethnomedicine. The in vitro cytotoxicity of the stem bark extract of C. africana and isolated cytotoxic compounds was investigated. Three resveratrol derivatives: (E)-resveratrol 3-O-rutinoside (1), 5-methoxy-(E)-resveratrol 3-O-rutinoside (2), and pinostilbene (3), together with 3-hydroxy-5-methoxybenzoic acid (4) were isolated from the methanol fraction of C. africana. Their structures were determined by extensive analysis of their HREIMS and NMR spectra. The cytotoxicity of the isolated compounds against four human carcinoma cells was determined using the MTT assay. Compound 1 displayed the highest antiproliferative effect on the cell lines, with IC50 values of 16.80, 21.74, 17.89, and 17.44 µM, against MCF7, A549, PC3, and HepG2 human cancer cell lines, respectively. In addition, compounds 1-3 showed low toxicity against normal human prostate cell line, with selectivity indices greater than five across the carcinoma cells, indicating that the compounds possess potential in the development of low-toxicity chemotherapeutic agents. These results support the traditional use of this plant in the treatment of cancer.

Acridone alkaloids from the stem bark of Citrus aurantium display selective cytotoxicity against breast, liver, lung and prostate human carcinoma cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Citrus aurantium L. (Rutaceae) is used, either singly or as a part of a polyherbal preparation, in Nigerian traditional medicine for the management of cancer and inflammatory diseases. Currently, there is a dearth of knowledge demonstrating its anticancer potential. AIM OF THE STUDY: This study was carried out to determine the in vitro cytotoxicity of the crude extract of the stem bark of C. aurantium, identify and isolate the bioactive constituents and to establish the cytotoxicity of such constituents. MATERIALS AND METHODS: The powdered bark of C. aurantium was extracted by MeOH at room temperature (25-34 °C) and the crude extract was partitioned successively, with n-hexane, dichloromethane and methanol. Amongst the fractions, the DCM fraction was the most active and compounds were isolated from this fraction using a combination of chromatographic techniques. The structures of the isolated compounds were elucidated by spectroscopic means (MS, 1D and 2D NMR). The cytotoxicity of the extract, and the isolated compounds were evaluated by the MTT assay against four human cancer cell lines: A549 (lung), HepG2 (liver), MCF7 (breast) and PC3 (prostate). The selectivity of the isolated compounds was assessed using the normal human prostate epithelium cells (PNT2). RESULTS AND DISCUSSION: Of the three plant fractions, the DCM fraction showed significant cytotoxicity, with its highest activity against A549 cells (IC50 = 3.88 µg/mL) and the least activity on HepG2 cells (IC50 = 5.73 µg/mL). Six acridone alkaloids, citrusinine-I (1), citracridone-I (2), 5-hydroxynoracronycine (3), natsucitrine-I (4), glycofolinine (5) and citracridone-III (6), were isolated from the DCM fraction of C. aurantium. The isolated compounds demonstrated potent to moderate cytotoxicity (IC50 = 12.65-50.74 µM) against the cancer cells under investigation. It is noteworthy that the compounds exerted cytotoxicity at least four times more selective towards the carcinoma cells than the PNT2 cells. CONCLUSION: The results obtained from this study have provided some evidence for the ethnomedicinal use of C. aurantium against cancer and the acridone alkaloids present in its stem bark, have appeared to be responsible for the anticancer effects.

Antimalarial and cytotoxic properties of Chukrasia tabularis A. Juss and Turraea vogelii Hook F. Ex. Benth.

Malaria, caused by plasmodium parasite, is at the moment the highest cause of morbidity and mortality in the tropics. Recently, there is increasing efforts to develop more potent antimalarials from plant sources that will have little or no adverse effects. This study is aimed at investigating the in vivo mice antimalarial and in vitro antiplasmodial effects of two Meliaceae plants commonly used in Nigerian ethnomedicine as part of recipe for treating malaria infection: Chukrasia tabularis and Turraea vogelii. Hot water decoction and methanol extract of both plants were evaluated for their antimalarial activity in vivo using the mice model assay and in vitro using the parasite lactate dehydrogenase (pLDH) assay. The extracts were also assessed for toxicity with brine shrimp lethality assay and in mammalian cell lines using the neural red assay. The in vivo mice model antimalarial study showed that the methanol extract of the stem bark of C. tabularis exhibited the highest % chemosuppression (83.65 ± 0.66) at the highest dosage administered (800 mg/kg) when compared with chloroquine diphosphate, the standard reference drug which had a % suppression of 90.36 ± 0.04 (p < 0.05). The in vitro antiplasmodial study indicated that the aqueous extract of the stem bark of C. tabularis displayed good activity against Plasmodium falciparum chloroquine-sensitive (D6) strain (IC50 of 10.739 µg/mL) and chloroquine-resistant (W2) strain. Chloroquine and artemisinin had <0.163 and <0.0264, respectively.

Larvicidal properties of simalikalactone D from Quassia africana (Simaroubaceae) Baill and Baill, on the malaria vector Anopheles gambiae.

BACKGROUND: Botanical and microbial insecticides have been increasingly used for the control of mosquito given their efficacy and documented nontoxic effects on non-target organisms. The discovery of new insecticides is imperative because of the development of resistance by the mosquitoes to the readily available insecticides. The aim of this study was therefore to isolate and characterize compounds from a local medicinal plant, Quassia africana Baill and Baill (Simaroubaceae) that were toxic to Anopheles gambiae. MATERIAL AND METHODS: The methanol extracts of the leaves, stem and roots of Quassia africana were tested against fourth instar larvae of An. gambiae. The root extract was partitioned into hexane, chloroform and ethyl acetate and the resulting extracts screened for larvicidal properties. The extracts and the fraction with the highest bioactivity were subjected to repeated column chromatography and isolated compounds evaluated for potential toxicity to An. gambiae larvae. The structure of the active compound was elucidated using spectroscopic techniques. The root extract showed the strongest activity profile (LC50 = 17.58 µg/mL). The chloroform soluble fraction obtained after partitioning the crude extract into solvents based on polarities was the most toxic. Further bio-activity-guided chromatographic separation of the chloroform fraction of the root extract led to the identification and isolation of a simalikalactone D as the larvicidal compound in Q. africana (LC50 = 1.25 µg/mL). RESULTS: Results suggest that Q. africana may serve as a source for vector control agent for malaria. CONCLUSION: Simalikalactone D was identified as the larvicidal compound in Q. africana (LC50 = 1.25 µg/mL).

In vivo antimalarial activity of Trichilia megalantha harms extracts and fractions in animal models.

The crude methanol extracts of leaf, stem bark, root bark and stem bark fractions of Trichilia megalantha (Meliaceae) were screened for in vivo antimalarial activities in mice against a chloroquine resistant Plasmodium berghei berghei ANKA clone using the 4-day suppressive test procedure. Chloroquine diphosphate was used as the positive control. The extracts demonstrated intrinsic antimalarial property. Of all the seven extracts studied, the stem bark gave the highest activity. At 200 mg/kg of mouse, the stem bark extract had complete suppression of parasite growth (100%). Least activity was observed for the leaf extract, while the root bark had a parasite suppression of 98.4% at 800 mg/kg comparable to that of Chloroquine. Percentage suppression of parasite growth on day 4 post-infection ranged from 3.1 to 96.1% in mice infected with P. berghei and treated with extracts and fractions of T. megalantha when compared with chloroquine diphosphate, the standard reference drug which had a chemosuppression of 96.2%. At 400 mg/kg, the stem bark chloroform fraction was the most active fraction with 89.1% parasite growth suppression followed by the ethyl acetate fraction (76.4%), hexane soluble fraction (54.8%) and methanol fraction (20.5%). The mean survival time of mice that received extract ranged from 8.75 ± 0.65 to 26.0 ± 1.2 days (increased as the dose increases to 800 mg/kg), which was statistically significant, except the lowest dose (100 mg/kg) compared to the negative control group mice (9.45 ± 0.6 days). The animals that were treated with Chloroquine had mean survival time of 23.5 ± 1.2 days.

Antitrypanosomal activity of some medicinal plants from Nigerian ethnomedicine.

Human African trypanosomiasis is a neglected tropical disease with complex clinical presentation, diagnosis, and difficult treatment. The available drugs for the treatment of trypanosomiasis are old, expensive, and less effective, associated with severe adverse reactions and face the problem of drug resistance. This situation underlines the urgent need for the development of new, effective, cheap, and safe drugs for the treatment of trypanosomiasis. The search for new antitrypanosomal agents in this study is based on ethnomedicine. In vitro antitrypanosomal activity of 36 plant extracts from 10 plant species from Nigerian ethnomedicine was evaluated against bloodstream forms of Trypanosoma brucei rhodesiense STIB 900. Cytotoxic activity was determined against mammalian L6 cells. Alamar blue assay was used to measure the endpoint of both antitrypanosomal and toxicity assays. The ethyl acetate extract of leaves of Ocimum gratissimum Linn. (Labiatae) showed the highest antitrypanosomal activity (IC(50) of 2.08 ± 0.01 µg/ml) and a high selective index of 29. Furthermore, the hexane, ethyl acetate, or methanol extracts of Trema orientalis (L.) Blume (Ulmaceae), Pericopsis laxiflora (Benth. ex Baker) Meeuwen, Jatropha curcas Linn. (Euphorbiaceae), Terminalia catappa Linn. (Combretaceae), and Vitex doniana Sweet (Verbenaceae) displayed remarkable antitrypanosomal activity (IC(50) 2.1-17.2 µg/ml) with high selectivity indices (20-80) for trypanosomes. The antitrypanosomal activity of T. catappa and T. orientalis against T. brucei rhodesiense (STIB 900) is being reported for the first time in Nigerian ethnomedicine, and these plants could be a potential source of antitrypanosomal agents.

Comparison of SYBR Green I-, PicoGreen-, and [3H]-hypoxanthine-based assays for in vitro antimalarial screening of plants from Nigerian ethnomedicine.

The standard method for in vitro antimalarial drug screening is based on the isotopic assay which is expensive and utilizes radioactive materials with limited availability, safety, and disposal problems in developing countries. The use of non-radioactive DNA stains SYBR Green I (SG) and PICO green (PG) for antimalarial screening had been reported. However, the use of the two DNA stains for antimalarial screening of medicinal plants has not been compared. Thus, this study compared SG, PG with the [(3)H]-hypoxanthine (HP) incorporation assays for in vitro antimalarial screening of medicinal plants. The 50% inhibitory concentration (IC(50)) values obtained using the three methods for antimalarial activity of medicinal plants and standard antimalarial drugs were similar. Data generated from this study suggests that the non-radioactive micro-flourimetric assay is sufficiently sensitive to reproducibly identify plant extracts with antimalarial activity from those lacking activity. The HP-based assay exhibited the most robust signal-to-noise ratio of 100, compared with signal-to-noise ratios of 7 for SG and 8 for PG. The SG-based assay is less expensive than the PG- and HP-based assays. SG appears to be a cost-effective alternative for antimalarial drug screening and a viable technique that may facilitate antimalarial drug discovery process especially in developing countries.

Traditional management of tuberculosis in Ogun State of Nigeria: the practice and ethnobotanical survey.

An ethnobotanical survey was conducted on plants used traditionally for the management of tuberculosis in five local government areas of Ogun State, Nigeria, in a bid to document herbs used in the management of tuberculosis with the aim of identifying possible drug lead from the phytomedicine of these communities. A semi-structured questionnaire was used to obtain the required information on the use of herbal remedies for the management. A total of 50 respondents made up of herbalists (40.0%), herb sellers (52.0%) and traditional medicine practitioners (8.0%) were interviewed in the study. The dominant age of respondents was in the range of 21-40 years (72.0%). Duration of treatment of tuberculosis with herbs was between 2-12 weeks. A total of 36 plants belonging to 20 families were proffered for the management of tuberculosis. Eighty four percent (42%) of the 50 respondents interviewed said that their clients observed no side effects and that the herbs were either available in the forest or purchased from the markets. Cola acumminata (fruit), Garcinia kola (leaf), Vitallaria parodoxa (oil), Costus afer (stem), Pycnanthus angolensis (stem bark) and Aframomum melegueta (fruit) were the most frequently mentioned herbs. The ethnomedicines of the studied areas of Ogun State, Nigeria seem to have a high potential as a source of drug discovery of anti-tuberculosis. This is of utmost importance because people living with human immunodeficiency virus (HIV) are susceptible to tuberculosis.