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Radix Bupleuri is one of the most widely used herbal medicines in China for the treatment of fever, pain, and/or chronic inflammation. Quercitrin, epicatechin, and rutin, the flavonoids present in Radix Bupleuri, have been reported to display anti-inflammatory, antitumor, and antioxidant biological activities among others. Sulfation has been reported to play an important role in the metabolism of flavonoids. In this study, we aimed to systematically identify the human cytosolic sulfotransferase enzymes that are capable of catalyzing the sulfation of quercitrin, epicatechin, and rutin. Of the thirteen known human cytosolic sulfotransferases, three (cytosolic sulfotransferase 1A1, cytosolic sulfotransferase 1C2, and cytosolic sulfotransferase 1C4) displayed sulfating activity toward quercitrin, three (cytosolic sulfotransferase 1A1, cytosolic sulfotransferase 1A3, and cytosolic sulfotransferase 1C4) displayed sulfating activity toward epicatechin, and six (cytosolic sulfotransferase 1A1, cytosolic sulfotransferase 1A2, cytosolic sulfotransferase 1A3, cytosolic sulfotransferase 1B1, cytosolic sulfotransferase 1C4, and cytosolic sulfotransferase 1E1) displayed sulfating activity toward rutin. The kinetic parameters of the cytosolic sulfotransferases that showed the strongest sulfating activities were determined. To investigate the effects of genetic polymorphisms on the sulfation of quercitrin, epicatechin, and rutin, individual panels of cytosolic sulfotransferase allozymes previously prepared were analyzed and shown to display differential sulfating activities toward each of the three flavonoids. Taken together, these results provided a biochemical basis underlying the metabolism of quercitrin, epicatechin, and rutin through sulfation in humans. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated the presence of the sulfated form of 6-gingerol, a major pharmacologically active component of ginger, in plasma samples of normal human subjects who were administered 6-gingerol. The current study was designed to systematically identify the major human cytosolic sulfotransferase enzyme(s) capable of mediating the sulfation of 6-gingerol. Of the 13 known human cytosolic sulfotransferases examined, six (SULT1A1, SULT1A2, SULT1A3, SULT1B1, SULT1C4, SULT1E1) displayed significant sulfating activity toward 6-gingerol. Kinetic parameters of SULT1A1, SULT1A3, SULT1C4, and SULT1E1 that showed stronger 6-gingerol-sulfating activity were determined. Of the four human organ samples tested, small intestine and liver cytosols displayed considerably higher 6-gingerol-sulfating activity than those of the lung and kidney. Moreover, sulfation of 6-gingerol was shown to occur in HepG2 human hepatoma cells and Caco-2 human colon adenocarcinoma cells under the metabolic setting. Collectively, these results provided useful information relevant to the metabolism of 6-gingerol through sulfation both in vitro and in vivo. [ABSTRACT FROM AUTHOR]