Skullcap (Scutellaria lateriflora)

Indications

Insomnia, anxiety, and nervous tension.

Mechanism of Action

The above-ground parts, principally the leaves and flowers, are used medicinally. Two important flavonoids found in Scutellaria are baicalin and wogonin. They are thought to be GABAergic, binding to the benzodiazepine site of the γ-aminobutyric (GABA) receptor, and thereby have a sedating and anxiolytic effect.¹ Scutellaria contains other notable flavonoids, including scutellarin, methoxyflavone, and catalpol. Other constituents include lignins, resins, tannins, and volatile oils.

Several other flavonoid constituents of Scutellaria, including baicalein; scutellarin; a flavone-glycoside 7-glucuronyloxy-5,6,2′-tri-hydroxyflavone (ikonnikoside I); and a flavanone-glycoside (dihydrobaicalin), were also found to bind to the serotonin receptor 5-HT7. The implications of that binding are currently unknown, as it is not known whether these constituents have an antagonistic or agonistic effect on the receptor. It has been speculated that Scutellaria’s effects on serotonin receptor 5-HT7 may at least be partially responsible for its reported sedative and relaxing effects.²

Evidenced-Based Research

Two common behavioral tests used to test anxiety levels in lab rodents are the open field test and the elevated plus maze (EPM) test. Rats and mice have a natural aversion to open spaces and are known to avoid them more frequently with increased anxiety levels. In one study, rats were fed an aqueous extract of Scutellaria and subjected to three behavioral tests to assess anxiety levels: open field, EPM, and the social interaction paradigm. A Scutellaria-free control group underwent the same tests. The Scutellaria rats were more likely to visit and stay in the center of a box (compared with the controls) in the open field test. The Scutellaria rats also spent more time in the open arms of the EPM compared to their peers in the control group. Both tests suggest an anxiolytic effect from the herb. The social interaction paradigm did not reveal a demonstrable effect from the Scutellaria extract, as the both the controls and the rats fed Scutellaria had similar social interaction rates. The authors of the study have speculated that perhaps Scutellaria may only be effective in certain forms of anxiety or that the extraction procedure, dose used, or duration of this test may have been less than ideal.³

A small, placebo-controlled, double-blind, crossover study of 43 human participants demonstrated that Scutellaria reduced symptoms of anxiety and depression in some individuals, without causing an observable reduction in energy or cognition. An overall enhancement of mood was also noted. In addition, no toxicity or adverse reactions were found. Participants were randomized to one of two groups. Group 1 was given Scutellaria followed by placebo. Group 2 was given placebo followed by Scutellaria. The dose of Scutellaria was 350 mg TID. By chance, all of the participants with moderate-to-severe baseline anxiety were in group 1. In this group, there was a significant reduction in Beck Anxiety Inventory (BAI) scores compared with placebo. In group 2, which included those with minimal anxiety, there was little room for the scores to go any lower. No significant improvement in BAI scores were observed for this group. The study authors speculated that there may have been some limitations of the study design. The low baseline anxiety scores of group 2 made it hard for improvement. Using notably anxious participants in the future may yield better results.⁴

Safety in Pregnancy and Breastfeeding

No specific contraindications are mentioned in traditional literature, and no information on the safety of Scutellaria in pregnancy or lactation could be found in scientific literature. No concerns have been identified.⁵

General Safety

Scutellaria seems to be very safe, with no common adverse reactions associated with its use. Products labeled as Scutellaria have been known to be adulterated with the herb germander (Teucrium spp.), which has a somewhat similar appearance to Scutellaria. Cases of toxicity reported in association with use of products labeled as Scutellaria are likely the result of adulteration with that herb.

Recently, an analysis of the literature on the hepatic effects caused by constituents found in Scutellaria and germander revealed that diterpenes found in germander caused severe and widespread damage, whereas related diterpenes in Scutellaria caused adverse effects that were limited to a few liver cells in a small percentage of tested animals.⁶

Dosage

Scutellaria is generally considered safe, even at doses of 1–2 g/day. Doses typically range from 100 to 500 mg of the above-ground parts taken two or more times a day.

Traditional Uses

Scutellaria is native to the midwestern and eastern United States, excluding the southeast, and southeastern Canada. Several Native American tribes used Scutellaria, but for the most part they used it differently than folk and eclectic American herbalists, who have used Scutellaria for centuries to calm the nerves. The Cherokee used the boiled root to treat diarrhea, kidney problems, and breast pains. The Iroquois made an infusion of the powdered roots of Scutellaria to treat smallpox.⁷

The eclectic physicians, in general, held Scutellaria in high esteem. In the 19th and early 20th centuries, they predominately used it as a nervine for conditions such as nervousness caused by physical ailments and mental exhaustion as well as heart disorders caused or exacerbated by anxiety. They also used Scutellaria as an antispasmodic for muscular spasms, hysteria accompanied by uncontrollable muscular action, tremors, convulsions, and chorea (involuntary, rapid, jerky, forceful movements caused by Huntington’s disease or other causes).⁸

References