In one aspect, nutraceutical compositions, methods of preparation and methods of use comprise a nutraceutical composition comprising an antimicrobial hevamine A-related protein from Momordica balsamina alone or in combination with one or more nutraceutical ingredients. In another aspect, a method of preventing or treating a microbial infection in a plant comprises applying an effective amount of a composition containing the hevamine A-related protein to a whole plant, plant part, or media in which the plant is growing. In a further aspect, the present application provides a transgenic plant stably transformed with a polynucleotide encoding the hevamine A-related protein.