Rhein, an anthraquinone derivative, has been employed widely, especially for the treatment
of intractable diseases like diabetic nephropathy, arthritis, and cancer in a unique action mechanism.
In the last decades, considerable efforts have been made in structural modification of rhein. This paper
reviewed patents on pharmacological activity and therapeutic application of rhein and its derivatives
from 1978 to 2018. Particularly, an analysis of patents was made, with the top 10 most valuable patents
presented, and the interpretation of the legal status of patents was given. Given the properties of
superior pharmacological activity, rich resources, cheap price, low toxicity, and mature extraction
process, it is believed that an in-depth investigation on rhein and its derivatives is worth trying.