Phyllanthin, the bitter principle of the leaves ofPhyllanthus niruri has been isolated in a crystalline condition and in good yield. It melts at 97–98°, has the molecular formula C21H22O7 and contains methoxyl and methylene-dioxy groups. Its important properties are described. A related crystalline substance, hypophyllanthin, which is not bitter, has also been isolated in a small yield. The leaves contain about 5% of wax which consists mostly of esters.