Effects of Gamma Irradiation on Seeds Germination, Plantlets Growth and In vitro Antimalarial Activities of Phyllanthus odontadenius Müll Arg

Aims: To increase the production of secondary metabolites of P. odontadenius using gamma radiation in order to amplify those with In vitro antimalarial activity.
Study Design: Laboratory experiment tests; Identification of plant material, Irradiation of seeds, In vitroculture of seeds, In situ culturing plantlets, Extraction of Phyllanthus odontadenius aerial parts, Phytochemical screening, In vitro antiplasmodial tests to determine the inhibition of concentration killing 50% of parasite population (IC50).
Place and Duration of Study: Department of Biotechnology and Molecular Biology, Department of Biochemistry: General Atomic Energy Commission, Regional Center of Nuclear Studies, P.O. Box. 868 Kin XI (DRC), National Institute of Biomedical Research (INRB) à Kinshasa/Gombe (RDC), UMR-MD3 Laboratory (Institute of the Biomedical Research of Army, Marseille/France. The experiments were conducted during January 2010 to June 2011.
Methodology: Seeds of P. odontadenius were obtained after oven drying at 45°C and they were irradiated by gamma-irradiation (137Cs) at dose ranging between 0 to 300 Grays (Gy). Seeds were germinated on Murashig and Skoog medium and plantlets were transferred in the tubes or in situ. In addition some parameters such as height, collar diameter, number of branches and biomass from first and second generations were analyzed. Phytochemical screening was released. The In vitro antiplasmodial activities assays on clinical isolates of P. falciparum or on resistant P. falciparum K1 to chloroquine was determined.
Results: Results showed that gamma irradiation had negative effects on growth parameters of P. odontadenius in the M1 and M2 generations with greater effects observed with treatment exceeding 100 Gy. For the In vitro antimalarial activities from to extracts obtained with aerial materials part from directly irradiated seeds (M1), the effects observed with extracts from M1 were higher than those from M2. For M1 extracts plants, IC50 values were ranged between 1.0±0.22µg/ml to 6.95±0.64µg/ml and between 1±0.05µg/ml to 10.45±1.18 µg/ml for M2 extracts plants on P. falciparum from to clinical isolates. With P. falciparum K1 strain, the IC50 values were ranged between 0.92±0.91–4.08±1.49 µg/ml for M1 and between 3.91±0.2.69–14.11±1.31µg/ml for M2 extracts. The best activities were observed with gamma-radiation doses exceeding 150 Grays (Gy).
Conclusion: Gamma-irradiation of P. odontadenius seeds induced reduction of parameters which decrease linearly with increasing irradiation doses. Synthesis of secondary metabolites increase in the second generation compared to the first one with a more important synthesis in phenolic compounds. The In vitroantiplasmodial activity on the clinical isolates P. falciparum or P. falciparum K1 showed low antimalarial activities from M1 and M2 controls (0Gy) than that of extracts from treated plants. The high inhibitory effects of crude extracts plants from treated seeds have justified the usefulness of gamma-irradiation in the increasing production of secondary metabolite against malaria in the Word particularly in DRC.