The present disclosure provides methods for killing the SARS CoV-2 virus in mammals and treating the Coronavirus Disease-19 (Covid-19) in mammals including humans using compositions including protocatechuic acid. The present disclosure provides methods and pharmaceutical and nutraceutical compositions that reduce or substantially eliminate the SARS CoV-2 virus in mammals. In one embodiment, a method of treating a mammal with Covid-19 is provided comprising administering protocatechuic acid to a mammal in need of such treatment a therapeutically effective amount of a protocatechuic acid composition.