Monoclonal antibodies (MAbs) against natural products with low?molecular weights have become an important tool when combined with other analytical systems. East blotting involves a typical staining system wherein, for example, glycosides can be blotted to a membrane and cross?linked and stained using MAbs. An immunoaffinity column combined with a monoclonal antibody allows a one?step purification of hapten compounds or preparation of a knockout extract that removes only the target hapten molecules from a crude extract. Here, we discuss the application of these extracts. Single?chain variable fragment (scFv) proteins have led to novel assay systems such as fluobodies or antibodies coupled with green fluorescent protein for natural products. A typical novel application of a scFv gene would be in the context of plant breeding; this is designated missile?type molecular breeding, intended to increase hapten molecule concentrations in transgenic plants.