Herbal liver protectants Milk thistle

At least one herbal remedy has shown considerable promise as a liver pro- tectant in conditions of this sort. Milk thistle has been widely used and

Chapter three: Digestive system problems

49 extensively investigated as a cure or preventive for a wide range of liver

problems. This herb consists of the ripe fruits, freed from their pappus (tuft of silky hairs), of Silybum marianum (L.) Gaertn. (family Asteraceae).

A crude mixture of antihepatotoxic principles was first isolated from the plant and designated silymarin. It is contained in the fruit in concentra- tions ranging from 1 to 4 percent. Subsequently, silymarin was shown to consist of a large number of flavonolignans, including principally silybin accompanied by isosilybin, dehydrosilybin, silydianin, silychristin, and possibly several others, depending on the variety examined. 102

Studies in small animals have shown conclusively that silymarin exerts a liver-protective effect against a variety of toxins, including those of the deadly amanita. Silybin has been investigated in several studies involving humans poisoned with the death cap mushroom, Amanita phal- loides. It was shown to be an effective prophylactic measure against liver damage if it is administered intravenously within twenty-four hours after mushroom ingestion; however, the rule here is “the sooner the better,” because there is a brief window of time after the ingestion of the poison- ous cyclic peptides found in the mushroom before they are taken up by the liver. If the silybin can bind to receptor sites on the outer liver cell membranes targeted by these toxins before the toxins bind, it can prevent the entry of the toxins into the cell and reduce the severe liver damage that can result in death. 103

Central to the use of milk thistle in the treatment of degenerative liver conditions is the ability of silymarin to increase protein synthesis in hepa- tocytes. These liver parenchymal cells make up the bulk of the organ and carry out the exquisitely complex metabolic processes responsible for the liver’s essential role in metabolism. The biochemical mechanism by which this increased protein synthesis is achieved is illustrated in Figure 3.1 .

Silymarin stimulates RNA polymerase I activity, possibly by activat- ing a promoter or enhancer site on the DNA that the polymerase uses as a template for the synthesis of ribosomal RNA. Ribosomal RNA is required for the formation of ribosomes in the cytoplasm, where protein synthesis takes place. Therefore, an increase in the amount of ribosomal RNA results in an increased number of ribosomes, with a resulting increase in protein synthesis (enzyme and structural protein). The increase in enzymes and structural protein stimulates the repair of injured cells and also increases the synthesis of DNA, resulting in an increase in mitosis and cell proliferation. 104,105 In addition, silymarin functions as a free-radical scavenger and antioxidant. 106

The German Commission E endorses use of the herb as a support- ive treatment for chronic inflammatory liver conditions and cirrhosis. Average daily dose is 12–15 g of powdered seed. 107 This is equivalent to about 200–400 mg of silymarin. Unfortunately, silymarin is very poorly soluble in water, so the herb is not effective in the form of a tea. Studies

50 Tyler's herbs of choice: The therapeutic use of phytomedicinals

Increased RNA polymerase I

activity Increased ribosomal RNA synthesis

Increased DNA synthesis Increased

Nucleus

mitosis and cell proliferation

Increased ribosome formation

Increased protein

Repair of

synthesis

damaged cell

Figure 3.1 Mechanism of action of silymarin on the repair of the hepatocyte. show that such a beverage contains less than 10 percent of the initial activ-

ity in the plant material. 108 Coupled with the fact that silymarin is rela- tively poorly absorbed (20–50 percent) from the GI tract, it is obvious that the administration of concentrated products is advantageous. Milk thistle is marketed in the United States in the form of capsules, usually contain- ing 200 mg each of a concentrated extract representing 140 mg of silymarin. Toxic effects resulting from the consumption of milk thistle have apparently not been reported.

The only other liver-protective herb that need be mentioned at all, and then only briefly, follows.

Schizandra Also spelled schisandra, this herb consists of the dried, ripe fruits of Schisandra chinensis (Turcz.) Baill. (family Schisandraceae). The fruits and seeds of this plant, native to China, have been extensively investigated

Chapter three: Digestive system problems

51 chemically and found to contain more than thirty different lignans,

including schizandrin, isoshizandrin, and gomisins A, B, C, D, F, and G. Some of these compounds have been studied in small animals for physi- ological activity. Several of them appear to protect the liver from toxic sub- stances. Even though a number of schizandra products or combinations are currently marketed, their safety and efficacy for any purpose, par- ticularly antihepatotoxic effects, remain unproven. 109 The consumption of

schizandra cannot be recommended at this time.

Herbal liver protectants Milk thistle