Trypanocidal and cytotoxic evaluation of synthesized thiosemicarbazones as potential drug leads against sleeping sickness.

Thiosemicarbazones have become one of the promising compounds as new clinical candidates due to their wide spectrum of pharmaceutical activities. The wide range of their biological activities depends generally on their related aldehyde or ketone groups. Here, we report the pharmacological activities of some thiosemicarbazones synthesized in this work. Benzophenone and derivatives were used with N(4)-phenyl-3-thiosemicarbazide to synthesize corresponding five thiosemicarbazones (1-5). Their structures were characterized by spectrometrical methods analysis IR, NMR (1)H & (13)C and MS. The compounds were then screened in vitro for their antiparasitic activity and toxicity on Trypanosoma brucei brucei and Artemia salina Leach respectively. The selectivity index of each compound was also determined. Four thiosemicarbazones such as 4, 2, 3 and 1 reveal interesting trypanocidal activities with their half inhibitory concentration (IC50) equal to 2.76, 2.83, 3.86 and 8.48 µM respectively, while compound 5 (IC50 = 12.16 µM) showed a moderate anti-trypanosomal activity on parasite. In toxicity test, except compound 1, which showed a half lethal concentration LC50 >281 µM, the others exerted toxic effect on larvae with LC50 of 5.56, 13.62, 14.55 and 42.50 µM respectively for thiosemicarbazones 4, 5, 3 and 2. In agreement to their selectivity index, which is greater than 1 (SI >1), these compounds clearly displayed significant selective pharmaceutical activities on the parasite tested. The thiosemicarbazones 2-5 that displayed significant anti-trypanosomal and cytoxicity activities are suggested to have anti-neoplastic and anti-cancer activities.

Chemical variation of essential oil constituents of Ocimum gratissimum L. from Benin, and impact on antimicrobial properties and toxicity against Artemia salina leach.

To determine the period of harvest that optimizes the antimicrobial activities of the essential oil of Ocimum gratissimum L. from Benin, aerial plant parts were collected at two vegetative stages (pre- and full-flowering) and three sampling times (7 am, 1 pm, and 7 pm). Extraction by hydrodistillation yielded between 0.65 and 0.78% of essential oils. Characterization of the oils by GC-FID and GC/MS analysis revealed the presence of monoterpenes (87.26-93.81%), sesquiterpenes (5.57-11.34%), and aliphatic compounds (0.15-0.18%), with p-cymene (1; 28.08-53.82%), thymol (2; 3.32-29.13%), γ-terpinene (3; 1.11-10.91%), α-thujene (4; 3.37-10.77%), and ß-myrcene (5; 4.24-8.28%) as major components. Two chemotypes were observed, i.e., a p-cymene/thymol and a p-cymene chemotype, for plants harvested at 7 am for the former and at 1 pm or 7 pm for the latter, respectively. The oils were fungicidal against Candida albicans, with the sample from full-flowering plants collected at 7 am being the most active (MIC = 0.06±0.00 mg/ml). The chemical variation of the oils also influenced the antimicrobial effect against Staphylococcus aureus; the most active oil was obtained from plants at the pre-flowering stage collected at 7 am (MIC=0.24±0.01 mg/ml). Escherichia coli was insensitive to the chemical variation of the oils (MICs of ca. 0.48±0.02 mg/ml for all oils). Moreover, the essential oils showed low toxicity against Artemia salina Leach larvae, with LC(50) values in the range of 43-146 µg/ml. This is the first study of the interaction between the daytime of collection and vegetative stage of the plants and the antimicrobial properties and toxicity of the essential oil of O. gratissimum from Benin.

Structural and antitrypanosomal data of different carbasones of piperitone.

This article reports data on four carbazones of piperitone: semicarbazone 1, thiosemicarbazone 2, 4-phenyl semicarbazone 3 and 4-phenyl thiosemicarbazone 4 prepared directly in situ from essential oil of Cymbopogon schoenantus, whose GC-FID and GC-MS analysis revealed piperitone as major component (68.20%). The structures of hemi-synthesized compounds were confirmed by high throughput IR, MS, 1H and 13C NMR based spectrometric analysis. Their antiparasitic activities were evaluated in vitro on Trypanosoma brucei brucei (Tbb). The compound 3 (IC50=8.63±0.81 µM) and 4 (IC50=10.90±2.52 µM) exhibited antitrypanosomal activity, 2 had a moderate activity (IC50=74.58±4.44 µM) but 1 was void of significant activity (IC50=478.47 µM). The in vitro tests showed that all compounds were less cytotoxic against the human non cancer fibroblast cell line (WI38) (IC50>80 µM) while only 2 (IC50=21.16±1.37 µM) and 4 (IC50=32.22±1.66 µM) were cytotoxic against the Chinese Hamster Ovary (CHO) cells and toxic on Artemia salina (Leach) larvae. Piperitone 4-phenyl semicarbazone 3, the best antitrypanosomal compound, showed also a selectivity index (SI) higher than 7 on the larvae and the tested cells and therefore might be further studied as antitrypanosomal agent. Also, all compounds except 3 showed selectivity between the two tested cell lines (SI>2). This data reveals for the first time the antitrypinosomal properties of thiosemicarbazones, their cytotoxicity on mammalian cells as well as their activities against Tbb and A. salina Leach.

In vitro antitrypanosomal and antiplasmodial activities of crude extracts and essential oils of Ocimum gratissimum Linn from Benin and influence of vegetative stage.

ETHNOPHARMACOLOGICAL RELEVANCE: Different parts of Ocimum gratissimum Linn are largely used in folk medicine for the treatment of many diseases, some of which related to parasitical infections as fevers and headaches. In order to validate their use and to clarify the plant part which possesses the best antiparasitic properties, we decided to evaluate the in vitro antiplasmodial and antitrypanosomal activities of essential oils and crude extracts from leaves, stems and seeds of Ocimum gratissimum as well as their cytotoxicity. MATERIALS AND METHODS: The essential oils and ethanol crude extracts of leaves and stems of Ocimum gratissimum from Benin, were obtained in pre and full flowering stages. Seeds obtained only in full flowering stage, were also extracted. The oils were isolated by hydrodistillation and analyzed by GC/MS and GC/FID. Extracts and essential oils were tested in vitro against Trypanosoma brucei brucei and Plasmodium falciparum. Cytotoxicity was evaluated in vitro against Chinese Hamster Ovary (CHO) cells and the human non cancer fibroblast cell line (WI38) through MTT assay to evaluate the selectivity and toxicity was assessed against Artemia salina Leach. RESULTS: The essential oils and non-volatile crude extracts of Ocimum gratissimum were more active on Trypanosoma brucei brucei than on Plasmodium falciparum (3D7). This activity varies according to the vegetative stage (pre and full flowering) and the plant part (seeds, stems and leaves) extracted. The best growth inhibition of Trypanosoma brucei brucei was observed with ethanol crude extracts of leaves (IC50=1.66 ± 0.48 µg/mL) and seeds (IC50=1.29 ± 0.42 µg/mL) in full flowering stage with good selectivity (SI>10). The chemical composition of the essential oil from aerial parts (47 compounds), characterized by the presence as main constituents of p-cymene, thymol, γ-terpinene, ß-myrcene and α-thujene, depends on the vegetative stage. The oil contained some minor compounds such as myrcene (IC50=2.24 ± 0.27µg/mL), citronellal (IC50=2.76 ± 1.55µg/mL), limonene (IC50=4.24 ± 2.27µg/mL), with good antitrypanosomal activities. These oils and crude extracts were not toxic against Artemia salina Leach and had a low cytotoxicity except leaves and seeds ethanol extracts obtained in full flowering which showed toxicity against CHO and WI38 cells. CONCLUSIONS: Our study shows that ethanol crude extracts of leaves and seeds of Ocimum gratissimum in full flowering stage can be a good source of antitrypanosomal agents. This is the first report about the relation between the plant part extracted, the vegetative stage of the plant, the antitrypanosomal and antiplasmodial activities and the cytotoxicity of essential oils and non-volatile extracts of Ocimum gratissimum from Benin.