RNA interference is a post transcriptional gene silencing mechanism that is triggered by double-stranded RNA (dsRNA). Various attributes of the 3' end structure, including overhang length and sequence composition, plays a primary role in determining the position of the Dicer cleavage in both dsRNA and unimolecular, short hairpin RNA (shRNA). The specificity and robustness of RNAi have triggered an immense interest in using RNAi as a tool in various settings. RNAi is a mechanism for controlling normal gene expression which has recently began to be employed as a potential therapeutic agent for a wide range of disorders, including cancer, infectious diseases and metabolic disorders. Clinical trials with RNAi have now begin, but major obstacles, such as off-target effects, toxicity and unsafe delivery methods, have to be overcome before RNAi can be considered as a conventional drug. It is also used as a tool to improve crops by providing resistance against parasites and modified versions of siRNA that are directed against disease causing genes are being developed, some of which are already tested in clinical trials. In this paper, we first reviewed the RNAi mechanism and then focussed on some of its applications in biomedical research such as treatment for HIV, viral hepatitis and several other diseases.

Background: Currently, cardiovascular disorders are the primary cause of mortality in the world and constitute a serious medical problem. Blood coagulation is an essential process to prevent excessive blood loss through injured blood vessels; however, abnormal blood clotting in the blood vessels can result in fatal cardiovascular disorders. This study investigated the in vitro anticoagulant activity of Meriandra dianthera crude extract and its fractions and their erythrocyte membrane stabilizing activity. Methods: The plant leaves were extracted by a decoction method and were further fractionated by a liquid-liquid partition with a solvent of crescent polarity. The in vitro anticoagulant activity of the plant extract and its fractions was assessed by PT and APTT assays, while the membrane stabilizing activity was determined through hypotonic induced hemolysis. Results:The crude aqueous leaf extract of Meriandra dianthera significantly (P < 0.001) prolonged the intrinsic clotting pathway measured by APTT by specifically acting on the intrinsic coagulation pathway. By using liquid-liquid fractionation, the residual aqueous fraction was identified as the fraction responsible for the anticoagulant activity of the crude extract as it significantly (P<0.001) prolonged APTT while the other fractions failed. Both the crude extract and its aqueous residue fraction did not affect the extrinsic coagulation pathway measured by PT. In the membrane stabilizing assay, crude extract and aqueous residue fraction showed the highest membrane stabilizing activity. Conclusion:The crude extract and its aqueous residue fraction showed a potent in vitro anticoagulant and membrane stabilizing activity, which shows the potential of the plant's leaves as a new source of bioactive molecules for coagulation-related disorders.

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