A new insight into cardiovascular protective potentials of hydroxylated xanthones

Natural products play important roles as origins of new cardiovascular drugs. Xanthones are polyphenolic compounds that carry a dibenzo-γ-pyrone skeleton and exhibit a broad range of pharmacological activities. The application of xanthones and their derivatives as drug leads has been an area of intense study due to a "privileged structure" of the xanthone skeleton. However, cardiovascular protective activity of simple hydroxylated xanthones, a subclass of xanthones characterized by the presence of one to four hydroxyl substituents, has never been discussed to date. This review aims to provide new insights into the cardiovascular protective effect of natural and synthetic hydroxylated xanthones with a focus on their structure-activity relationship. The activity of hydroxylated xanthones on cardiovascular disease risk factors such as atherosclerosis, hypertension, diabetes and others was also discussed. The results showed that the cardiovascular protective activity of hydroxylated xanthones is dependent on the number and position of hydroxyl substituents attached to the benzene ring skeleton. Hydroxyxanthones with a higher number of hydroxyl substituents or with a presence of -OH at the C-3 position of the skeleton were found to exhibit higher activity. Recent findings revealed that the configuration of hydroxyl side groups may also be important. Furthermore, 1,3,5,6-tetrahydroxyxanthone (7) could be a promising lead for novel anti-hypertensive drugs. In conclusion, the evidence which support the use of hydroxylated xanthones as leads for novel cardioprotective, anti-atherosclerotic and anti-diabetic drugs is generally lacking in the literature. More works are warranted in these areas to clarify whether hydroxyxanthones are promising leads for novel cardiovascular drugs.