Rubia. Rubia cordifolia . Rubia tinctorum . Rubia cordifolias . Rubia tinctorums . Rubias . cordifolia, Rubia . tinctorums, Rubia . A plant genus of the family RUBIACEAE. The root is a source of red dyes (madder color and 1,2,4-trihydroxy-9,10-anthracenedione) and ANTHRAQUINONES. . 0.54