Viruses are microorganisms that infect all kinds of living organisms including plants, and cause remarkable lose in crop production. Although pesticides showed that they can protect plants from pest infections, there are no effective substances that can be used as potent virucides. Therefore, there is a continuous demand to produce chemicals in order to stop and cure viral infections in plants. However, toxicity and carcinogenicity issues were always attributed to chemical pesticides. Screening of natural products shined in the dark to find new safe virucides. The philosophy of selecting those plants is oriented towards plants that can protect themselves from viral infections. Plants have been reported as virus inhibitors and are able to prevent infection of viruses by inducing systemic resistance in noninfested parts of the plants, such as Boerhaavia diffusa, Clerodendrum aculeatum. Other plants defend themselves against virus infections; these plants contain ribosome inactivating proteins [RIPs], such as Phytolacca Americana, Mirabilis jalapa, Dianthus caryophullus. The methods used for extraction, separation, identification of those antiviral compounds are documented and discussed in this review.

Cucumber mosaic cucumovirus (CMV) was isolated from lettuce plants (Lactuca sativa)showing virus like symptoms. Isolation was performed depending on specific polyclonal antibodies and Chenopodium quinoa as a local lesion host. Virus was purified from 200 gm of virus-infected Nicotiana tabacum cv. White Burley leaves giving A 260/280 ratio of 1.21 and a yield of 1.7 mg. Purified virus preparation was used for rabbit immunization to produce specific polyclonal antibodies. IgGs were purified and evaluated by indirect enzyme linked immunosorbant assay (I-ELISA) to determine the dilution end point which found to be 1:512. Electron micrographs showed spherical virus particles of about 30 nm in diameter. Virus coat protein (CP) molecular weight was determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), giving a single band of 25 kDa within resolving gel. Immunocapture-reverse transcriptase-polymerase chain reaction (IC-RT-PCR) was used for the amplification of CMV coat protein gene (cp), the appearance of 657 bp bands confirmed the expected size of such gene. Comparing virus cp gene sequence with the sequences of seven overseas isolates confirmed that the under study isolate was related to the CMV subgroup I. ª 2013 Production and hosting by Elsevier B.V. on behalf of Faculty of Agriculture, Ain Shams University.