The disclosure relates to a method of inhibiting synthesis of viral DNA in a mammal infected with a hepatitis B virus. This method includes administering at least one Phyllanthus component or substance to a mammal infected with the hepatitis B virus. It also includes inhibiting hepatitis B viral DNA synthesis in the mammal using the Phyllanthus component or substance. The disclosure also relates to a method of inhibiting viral gene expression in a mammal infected with a hepatitis B virus. This method includes administering at least one Phyllanthus component or substance to a mammal infected with the hepatitis B virus. It also includes inhibiting expression of at least one hepatitis B viral gene in the mammal using the Phyllanthus component or substance. These methods may form part of a method of preventing or treating hepatitis B infection.