Scientific Name(s): Polygala senega L.
Common Name(s): Milkwort, Mountain flax, Polygalae radix, Rattlesnake root, Seneca snakeroot
Senega root is an uncommon perennial herb found throughout eastern North America1; it has "endangered" status in Connecticut, Maine, and New Jersey and "threatened" status in Maryland.2 The plant grows to approximately 0.5 m in height and has unbranched stems arising from a branched root.1, 3 The leaves are small, alternate, and narrowly lanceolate. Numerous pinkish-white or greenish-white flowers are crowded on a terminal spike. The root is twisted and has an irregular, knotty crown with a distinctive ridge. Senega's faint, sweet scent is similar to that of methyl salicylate.3 The variety P. senega var. latifolia Torr. & Gray has been distinguished; it grows in the same habitat but differs from P. senega in the size of its leaves and flowers and in its slightly later flowering period. Related species include Polygala tenuifolia Willd., Polygala reinii Franch., Polygala glomerata Lour., and Polygala japonica Houtt., all of which are used in Asia in a similar manner to P. senega.
Senega root was used by eastern American Indian tribes, including the Seneca tribe (from whom its name is derived), to treat rattlesnake bites1; however, early European observers gave little credence to this use. Colonists and Europeans used senega root as an emetic, cathartic, diuretic, and diaphoretic, and in treatment of pulmonary diseases (such as pneumonia, asthma, and pertussis), gout, and rheumatism.4 Its main use in the 19th century was as an expectorant cough remedy. It was included in the US Pharmacopeia from 1820 to 1936 and in the National Formulary from 1936 to 1960.
Seneca snakeroot contains a series of saponins constructed from the 2,3,27-trihydroxy-oleanane 23,28-dioic acid triterpene skeleton (presenegenin), with a single sugar attached at position 3 and a 4- to 6-sugar chain appended at position 28. A variety of methoxy-cinnamate esters are attached at the internal sugar of the C-28 chain.5, 6, 7, 8, 9, 10, 11, 12 These saponins have been named senegins Ι through ΙV and senegasaponins A through C. The senegins can be analyzed by high-performance liquid chromatography.13 Several other species of Polygala (see Botany) contain distinct but very similar saponins based on the same sapogenin.14 An extensive series of ester oligosaccharides, senegoses A through O, have been isolated from P. senega var. latifolia.15, 16, 17 The root also contains a small amount of methyl salicylate, which is responsible for its characteristic wintergreen scent.
Uses and Pharmacology
The antitussive effect of senega root has generally been attributed to the saponin content of the plant, which is consistent with the general detergent property of saponins in breaking up phlegm.1 In addition, senega is thought to act by irritation of the gastric mucosa followed by a reflex action, which stimulates an increase in bronchial mucous gland secretion. However, most of the available information about senega's antitussive properties is anecdotal.
Animal and in vitro data
In a study of anesthetized dogs, senega syrup dosed orally at 3 mL/kg (about 90 mg/kg) increased the volume output of respiratory tract fluid within 5 minutes of administration; the increase continued at 30 minutes following administration.18
In one study, a fluid extract of senega root reduced mucus viscosity in patients with bronchiectasis.3
Animal and in vitro data
In studies evaluating the hypoglycemic effects of senega saponins in mice with and without diabetes, hypoglycemic activity was observed in normal and diabetic mice, but not in mice with streptozotocin-induced diabetes.10, 11, 12, 19, 20, 21 Thus, these compounds have activity relevant to non–insulin-dependent diabetes. This activity is most potent when the saponins are injected intraperitoneally but can also be detected with higher oral doses. The same saponins also substantially reduced alcohol absorption when given orally to rats 1 hour before alcohol consumption.10, 11, 12
In a study investigating an aqueous extract of the related species P. tenuifolia, a potent blocking effect on inflammatory processes in cultured mouse astrocytes was observed. Substance P– and lipopolysaccharide-induced production of tumor necrosis factor and interleukin-1 (IL-1) was blocked by a P. tenuifolia extract at low concentrations.22 It is possible that a systemic anti-inflammatory effect may be the result of a similar mechanism.
No biological activity has been reported for the oligosaccharides of senega root. Senegose A was inactive in the previously described hypoglycemia model.21
Research reveals no clinical data regarding the use of senega root for its hypoglycemic effects.
Animal and in vitro data
In a murine model, P. senega saponins increased antibody response to ovalbumin antigens in mice. These effects were similar to those of saponins from Q. saponaria but were less toxic, suggesting a potential role as an adjuvant in vaccines.23 Another study demonstrated similar effects in mice immunized with ovalbumin, with no P. senega saponin effect detected 10 days after immunization; in another arm of this study, P. senega saponins increased the immunoglobulin G response to rotavirus in immunized hens.24 In an in vitro study, senega saponins exerted antiangiogenic activity against human umbilical vein endothelial cells.25
A cell-screening assay of several P. senega extracts revealed dose-dependent anti-inflammatory effects, such as reductions in levels of IL-1beta, IL-6, and tumor necrosis factor alpha.26
Research reveals no clinical data regarding the use of senega root for its immunological effects.
Animal and in vitro data
In mice inoculated with sarcoma S180 cells, the senega saponin senegin III dosed at 2.5 mg/kg inhibited tumor growth in a manner similar to cisplatin. In addition, the combination of senegin III with cisplatin resulted in greater growth inhibition compared with the control group.25
In in vitro and an in vivo models in mice, P. senega was beneficial in the treatment of lung cancer. Administration of senega 50 and 100 mg/kg in mice with long-term exposure to a carcinogen modulated the expression of signal proteins.27 Similarly, an ethanolic root extract of P. senega reduced DNA damage as well as tumor nodules and tumor growth in mice with benzo[a]pyrene-induced lung cancer.28 Nanoencapsulation of an ethanolic root extract of P. senega was associated with greater inhibition of cancer cell growth, better bioavailability, and increased cellular entry compared with the non-nanoencapsulated ethanolic root extract of P. senega.29
Research reveals no clinical data regarding the use of senega root for its anticancer effects.
Pregnancy / Lactation
None well documented.
High doses of powdered senega root (more than 1 g) or tincture are emetic and irritating to the GI tract.31 The use of senega root is contraindicated during pregnancy, and in peptic ulcer disease or inflammatory bowel disease.34 Senega may exacerbate inflammatory conditions of the GI tract.
When investigated for their immunological potential as adjuvants in vaccinations, saponin fractions of P. senega were less toxic than those from Q. saponaria, which have traditionally been used as adjuvants for veterinary vaccines.24
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