Scientific Name(s): Scutellaria lateriflora L.
Common Name(s): Helmetflower, Hoodwort, Mad-dog weed, Scullcap, Skullcap
Scullcap (S. lateriflora), a member of the mint family, is native to the United States where it grows in moist woods. Although it is widely distributed throughout large regions of North America, there are related species found as far away as China. There are over 300 species of Scutellaria worldwide. Common scullcap (Scutellaria lateriflora) is the best known of these species.
Scullcap is an erect perennial that grows to 1 m in height. Its bluish flowers bloom from July to September. Official compendia recognize only the dried overground portion of the plant as useful; however, some herbal texts list all parts as medicinal.1 The aerial parts of the plant are collected during the flowering period, typically August and September. It is important to note the difference between American skullcap (S. lateriflora) and S. baicalensis (otherwise known as Chinese skullcap), which is a related plant.2 The members of this diverse genus are not generally interchangeable.2 A number of species have been used medicinally, and the most common European variety is S. baicalensis, a native of East Asia (see Baical Skullcap monograph).
Scullcap appears to have been introduced into traditional American medicine toward the end of the 1700s, when it was called mad-dog skullcap because of its use as a treatment for rabies. It was later used as a tonic, particularly in proprietary remedies for "female weakness."3 The plant was reputed to be an herbal tranquilizer, particularly in combination with valerian, but has fallen into disuse.
Scullcap has traditionally been used to treat nervousness, irritability, and neuralgia, as well as for its sedative properties.
The various species of Scutellaria contain several flavonoid glycoside pigments. These include scutellarein, wogonin, isoscutellarein, and baicalin. A diterpenoid (scuterivulactone) has also been identified.4
The aboveground parts of S. lateriflora have been found to contain neoclerodane diterpenes5 flavones, and flavone glucuronides.6 The flavonoids include baicalin, lateriflorin, dihydrobaicalin, and baicalein, which were quantitatively determined by liquid chromagraphy with ultraviolet detection/MS, and thin-layer chromatography. Adulteration of S. lateriflora with species of germander was detected by microscopy and by the presence of phenylpropanoids such as teucreoside, which were not found in scullcap.7
Uses and Pharmacology
Sialic acids are widely distributed in tissues as constituents of glycolipids and glycoproteins. They are present in mucus secretions and cell membranes where they are thought to be the sites at which viruses attach and penetrate the cell wall. Serum sialic acid is known to increase in certain disease states (eg, cancers, rheumatic diseases, infections, inflammations), and it has been postulated that an inhibitor of sialidase, such as scullcap extract, may have a therapeutic application.
Most research to date focused on the baical skullcap (S. baicalensis), which is used to treat inflammation and atherosclerosis, has antibacterial, antiviral, antioxidant, and antithrombic properties. Few studies have been carried out on S. lateriflora and further work is needed on this species.
One study assessed the anxiolytic efficacy of S. lateriflora in 2 animal test models to verify the traditional claims of anxiolytic activity. The results of the behavioral test indicated effects on anxiety levels in rats. The results of the study indicate that S. lateriflora has multiple active compounds and warrants further study to determine its potential to become a popular anxiolytic phytomedicine.8
A double-blind, placebo-controlled study in 19 healthy volunteers aimed to clarify the effectiveness of S. lateriflora in reducing anxiety. Subjective end points were used and assessed the effects of the preparations on patients' energy, cognition, and anxiety. A greater degree of sedation was seen at higher doses. The data produced indicate an anxiolytic property of S. lateriflora in comparison to placebo.2
Teas prepared from Scutellaria species have demonstrable in vitro antibacterial and antifungal activity.9
Comparison studies with other herbal anxiolytics and prescription medicines are needed to define more specifically the clinical potential of S. lateriflora as an anxiety treatment. Further studies are needed to validate the results of limited studies and subjective end points used. Clinically validated endpoints are needed in clinically impaired populations to further determine the clinical effect of S. lateriflora.
The effect of scullcap on mood was assessed in 31 healthy volunteers (6 men) 19 to 66 years of age who were randomized to 350 mg of S. lateriflora (whole aerial parts, not a standardized extract) 3 times daily or placebo for 2 weeks in a double-blind fashion and then crossed over to other treatment. Recruitment was generally based on persistent stress, anxiety, mood swings, irritability, poor sleep, or difficulty coping, as well as the inclusion of nonanxious participants. Exclusion criteria included a history of behaviors, conditions, or medications affecting the CNS. Overall, 81% of the group had a Beck Anxiety Inventory (BAI) score of 15 or less, which is considered mildly anxious at most. Although no significant difference was found between treatments measured on BAI scores, changes in total mood disturbance were significantly better with skullcap (P < 0.001). Specifically, a significant group × treatment interaction was observed for the Depression-Dejection state and an enhanced effect of skullcap for the Vigor-Activity state with a 20% increase in energy levels. A potential carryover effect for scullcap was further analyzed and a highly significant improvement in total mood disturbance (P < 0.001) was observed, an effect not seen with placebo.12
Not enough is known about American skullcap to recommend its use to children younger than 18 years of age.
No recent well-controlled studies of American skullcap have been carried out in humans. Doses of American skullcap should be limited to no more than the package recommendation.
Typical doses (see individual product information):
Dried herb: 1 to 2 grams 3 times/day.
Tea: 240 mL 3 times/day (pour 250 mL of boiling water over 5 to 10 mL of the dried herb and steep for 10 to 15 minutes).
Tincture: 2 to 4 mL 3 times/day.
Pregnancy / Lactation
Documented adverse effects. Avoid use. May inhibit pituitary and chorionic gonadotropins, as well as prolactin.10
None well documented. However, because American skullcap may promote sleepiness, it may intensify the effects of drugs that also cause drowsiness. The effects of the drug may be exaggerated, resulting in sedation or mental impairment.
The FDA presently designates scullcap as a herb of undefined safety.8 Minor and infrequent side effects were reported with the treatment for mood, and included vivid dreams (n = 1), feeling spaced out (n = 1), mild digestive disturbances (n = 4), and a constant taste of salt (n = 1). Of the 26 participants who completed a symptom diary, the conditions that reportedly resolved or improved corresponded with some of those noted for S. lateriflora related to allergies, inflammation, anxiety-related digestive problems, muscle tension and pain, headaches, and menstrual-related problems.12
According to the FDA, an overdose of the tincture causes giddiness, stupor, confusion, twitching of the limbs, intermission of the pulse, and other symptoms indicative of epilepsy.11 Exceptionally large doses have resulted in seizure-like movements.
No data exist demonstrating liver toxicity on an experimental basis, or with any of the scullcap species as a solitary medicament.2 Other species of the genus have been implicated in reported cases of hepatotoxicity.
This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.
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