I like Grapeseed Extract as a general antioxidant and vascular protectant, it also has some study as a kidney and liver aid.
"Grape Seed Extract. Known for its powerful antioxidant qualities, grape seed extract also acts as a smooth muscle relaxant in blood vessels to combat hypertension. Ray et al. (2000) studied the protective effects of grape seed extract against biological, pharmacological, and toxicological effects of certain drugs to the kidneys, lungs, and heart in mice (acetaminophen, amiodarone, and doxorubicin). Ray et al. (2000) found that "grape seed extract preexposure prior to acetaminophen, amiodarone, and doxorubicin provided near complete protection in terms of serum chemistry changes and significantly reduced DNA fragmentation." Moderate to massive tissue damage occurred by all three drugs in the absence of grape seed extract. Bagchi et al. (2000) also found that grape seed extract "demonstrated excellent protection against acetaminophen overdose-induced liver and kidney damage."