Bupleurum contains constituents known as saikosaponins that appear to account for much of the medicinal activity of the plant. Test tube studies have shown that the sho-saiko-to combination can increase production of various chemicals (known as cytokines) that immune cells use to signal one another.19 Test tube studies have also found that saikosaponins can inhibit growth of liver cancer cells,20 and are anti-inflammatory.21, 22
Human trials, only one double-blind, have shown that the bupleurum-containing formula sho-saiko-to may help reduce symptoms and blood liver enzyme levels in children and adults with chronic active viral hepatitis.23, 24, 25, 26 Most of these studies were in people with hepatitis B infection, though one preliminary human trial has also shown a benefit in people with hepatitis C.27 Sho-saiko-to was also found, in a large, preliminary (but not double-blind), study to decrease the risk of people with chronic viral hepatitis developing liver cancer.28
Sho-saiko-to has also been used to reduce symptoms of and possibly decrease the severity of liver cirrhosis, though clinical studies on this condition are generally lacking. One randomized trial (it was unclear if this trial was double-blind) found that sho-saiko-to could reduce the rate of liver cancer in people with liver cirrhosis.29
Several uncontrolled trials in Japan have shown that sho-saiko-to or very similar traditional Japanese and Chinese herbal formulas (all containing bupleurum) can reduce seizure frequency and/or severity in people with epilepsy that does not respond to anti-seizure medications.30, 31, 32, 33 However, double-blind trials are still needed to determine the importance of these findings.
Sho-saiko-to has been found to inhibit human immunodeficiency virus (HIV) in the test tube.34 Yet, it is unclear to what degree bupleurum or saikosaponins contributed to this effect. Sho-saiko-to also increased the efficacy of the standard anti-HIV drug lamivudine in the test tube.35 Human data are lacking on the benefit of sho-saiko-to or bupleurum in people with HIV infection or acquired immunodeficiency syndrome (AIDS).