Skullcap

Background & General Info

Belonging to Lamiaceae, or the mint family, skullcaps are slender flowering herbs that are extensively distributed over temperate regions and tropical mountains worldwide. [1] Its name comes from the similarity of its calyx at the flower’s base to the small helmets common during the Medieval Period. [1] Skullcaps are members of the genus Scutellaria, which comprises about 350 species that are widespread across Europe, the United States, and East Asia. [2] In the 19th century, skullcaps were known in America as “mad dog”; at present, the plant is also popularly called hoodwort, helmet flower, and hooded willow herb. [1] Skullcap can commonly pertain to either the American skullcap (Scutellaria lateriflora) or Chinese skullcap (Scutellaria baicalensis), both of which possess non-identical therapeutic utility. [3] Currently, skullcaps have become popular not only as drought-tolerant, showy blooms in southern gardens but also as a botanical medicine typically incorporated as a vital component in many over-the-counter herbal supplements. [4]

Skullcap - Botany

In general, member species of the genus Scutellaria are herbaceous, rarely shrubby perennials with opposite, ovate, and serrate leaves attached to hairy, branched stems, which are supported by fibrous, yellow creeper roots. [1] The floral leaves are typically bract-like apically. [5] Blossoming from May to August, tube-shaped, hooded, blue to lavender flowers emerge in racemes in axillary, opposite, or sometimes alternate arrangement from the leaf axils and possess two lips, the upper lip being the hood and the lower lip having two shallow lobes. [1][5] The short tubular calyx from which the plant is named after is dorsiventrally flattened, with two closed lips that ultimately divide to the base along the sutures in the fruit. The deciduous upper lip has a transverse, rounded, concave, scale-like scutellum or “shield”. [5]

Skullcap - History & Traditional Use

Traditional medicinal systems of China, India, Japan, Korea, and other European and North American countries used skullcap as readily available cures. [1] A few Scutellaria species are believed in traditional Chinese medicine to eliminate the “heat evil” and rebuke superficial evils. [2] The American skullcap is traditionally regarded as an herbal remedy for stress and anxiety and has been widely prescribed as a sedative and treatment for several nervous disorders. [6][7] In Western herbal medicine, it has a long history of use as a nervine that diminishes anxiety, sleeplessness, and spasms and calms the nerves [4] and it was sometimes seen in herbal smoking mixtures. Native Americans and Europeans in particular traditionally utilize the aerial parts of Scutellaria lateriflora as a nerve tonic, sedative, and anticonvulsant. [8]

Chinese herbalists have used the dried roots of Chinese skullcap as a medicine for thousands of years. The preparation produced from the plant’s roots, called huang-qin, is officially listed in the Chinese Pharmacopoeia and is prescribed as treatment for diarrhea, dysentery, hypertension, hemorrhage, insomnia, inflammation, and respiratory infections. [9]

Skullcap - Herbal Uses

Dried roots of the Chinese skullcap are commonly prepared as a decoction or as a tincture that is applied as remedy for hepatitis, tumors, diarrhea, and inflammatory diseases. [10] The Chinese skullcap has also been clinically utilized as a treatment of hyperlipidemia, atherosclerosis, hypertension, dysentery, and the common cold. [11] According to numerous studies, the flavones identified in Scutellaria baicalensis exhibit a broad range of pharmacological activities, including anticancer, hepatoprotective, antibacterial, antiviral, antioxidant, anticonvulsant, and neuroprotective properties. [9]


Skullcap - Constituents / Active Components

Results of the characterization carried out by Zhang et al. (2009) determined phenolic compounds, especially flavonoids, as the predominant compounds of American skullcap; these researchers were able to isolate 12 phenolic compounds, including 10 flavonoids and 2 phenylethanoid glycosides, from the plant. [8] On the other hand, the roots of Chinese skullcap contain flavones such as baicalin, wogonoside, and their aglycones baicalein and wogonin, respectively, as its major bioactive constituents. [9] Han et al. (2007) conducted liquid chromatography coupled with electrospray ionization mass spectrometry on Chinese skullcap roots and identified 26 flavonoids, including 5 C-glycosides, 12 O-glycosides, and 9 free aglycones. [10] A 2003 screening of the main flavonoids of Scutellaria baicalensis roots using a simple RP-HPLC method determined baicalin (8.12%) and wogonin glucuronide (2.52%) as the chief components. [12]

Skullcap - Medicinal / Scientific Research

Anti-anxiety: In vivo trials investigating the anti-anxiety effects of orally administered American skullcap extracts on the behavior of rats pointed out noteworthy increases in the number of entries into the center of an “open field arena,” number of unprotected head dips, and length of time spent on the open arms of the elevated plus-maze. [7] A 2014 randomized, double-blind, placebo-controlled crossover study demonstrated the ability of American skullcap to significantly improve global mood in human volunteers without decreasing energy or cognition. In this trial, 350 mg of American skullcap and placebo were randomly administered to 43 study participants three times daily for 2 weeks. Although no significant difference was observed between skullcap and placebo in terms of Beck Anxiety Inventory scores, a considerable group effect that implied skullcap’s “carryover effect” was noted. However, the American skullcap treatment led to a highly significant decrease in the pretest Total Mood Disturbance scores of the Profile of Mood States scale, which the placebo did not affect at all. [6]

The compounds that American skullcap contains appear to vastly contribute to its anti-anxiety property. The flavonoid baicalin and its aglycone baicalein, which had been identified in 50% ethanol extract and 95% ethanol extract of American skullcap, bind to the benzodiazepine site of the gamma-aminobutyric acid (GABA) receptor and are hence GABA receptor agonists. [7] In the study of Xu et al. (2006), treatment using baicalin at a dose of 7.5–30 mg/kg presented anti-anxiety effects in mice upon their assessment in elevated plus maze; specifically, this naturally occurring flavonoid extensively increased the entries into and the time spent in open arms and did not produce motor-depressive and myorelaxant side effects in the hole board and horizontal wire tests, respectively, which are frequently observed with anxiolytic drugs. When 3.75 mg/kg baicalin was coadministered with 0.25 mg/kg dl-tetrahydropalmatine, an anxiolytic–hypnotic alkaloid, and with 0.5 mg/kg diazepam, a popular drug used for short-term relief of anxiety disorder symptoms, it generated an additive anxiolytic effect. [13] GABA, a major inhibitory neurotransmitter, had also been quantified in the American skullcap water and ethanol extracts (approximately 1.6 mg/g), whereas glutamine had been found in the water extract (31 mg/g). [7]

Antioxidant: A 2003 evaluation of the antiradical property of Scutellaria baicalensis root flavonoids confirmed the significant scavenging ability of baicalin and baicalein in DPPH radical-generating system. In the presence of baicalin and wogonin glucuronide, the production of OH radicals also considerably diminished. The study concluded that baicalin is primarily responsible for the DPPH scavenging activity of Scutellaria baicalensis extract, with wogonin glucuronide and other flavonoids likely contributing to the extract’s ability to scavenge OH radical. [12]

The results of a 2011 Polish study indicated that dietary skullcap root supplementation may boost antioxidant systems and provide protection high-cholesterol diet in rabbits. After 6 weeks, rabbits fed with Scutellaria baicalensis roots manifested no adverse effects on their blood parameters such as red blood cell (RBC) and hemoglobin (Hb) levels. Rabbits fed with a cholesterol diet were characterized with a decrease in erythrocyte glutathione peroxidase (GSH-Px) activity and in erythrocyte superoxide dismutase (SOD) activity. In comparison, those on a diet with a 1% pure cholesterol supplement and a 9% skullcap root supplement demonstrated a significantly higher GSH-Px activity and enhanced erythrocyte SOD activity (a 23% increase with respect to those fed with cholesterol supplement only). [14]

Anticancer: Ye et al. (2002) reported the anticancer activity of Scutellaria baicalensis in vitro against human cancer cells. Treatment using Scutellaria baicalensis at different concentrations (0.1–100 mg/mL) for 72 hours strongly hampered the growth of cell lines from the most common human cancers, namely, squamous cell carcinoma (SCC-25, KB), breast cancer (MCF-7), hepatocellular carcinoma (HepG2), prostate carcinoma (PC-3 and LNCaP), and colon cancer (KM-12 and HCT-15). Additionally, Scutellaria baicalensis extract was determined to dose-dependently reduce the levels of prostaglandin E2 and to prevent its production. Such observation suggested that the ability of the plant to suppress the growth of cancer cells is likely related to its inhibition of the activity of cyclooxygenase-2 (COX-2). [15] Ye et al. (2009) had also shown that the Chinese skullcap intensely blocks the in vitro cell growth of hepatocellular carcinoma cells by arresting their G(2)/M phase and largely affects the cell signaling networks, which results in an inhibition of cell proliferation. [16]

Antiallergic: In a 2012 study, the Chinese skullcap had been confirmed to display antiallergic effect in vivo and in vitro, preventing passive cutaneous anaphylaxis reaction, diminishing the release of histamine by peritoneal mast cells of rats, and downregulating the expression of numerous inflammatory mediators. Its pretreatment in human mast cells also restored the expression of interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) but suppressed the expression of mitogen-activated protein (MAP) kinase. [17]

Anti-obesity: The potent anti-obesity and antidyslipidemic properties of Scutellaria baicalensis extract had been demonstrated by a 2013 Korean study in type 2 diabetic mice. Daily oral administration of the extract for 4 weeks had been shown to improve their weight gain and ameliorate hypertriglyceridemia and hyperinsulinemia in diabetic mice and to decrease the levels of plasma alanine aminotransferase (ALT) in obese mice. The livers of mice also manifested restored metabolic process and insulin signaling pathways. [11]

Anticonvulsant: The results from the study of Zhang et al. (2009) pointed out the anticonvulsant activity of American skullcap in rodent models of acute seizures induced by pilocarpine and pentylenetetrazole. [8] Park et al. (2007) found that wogonin, an anxiolytic and neuroprotective flavone isolated from Scutellaria baicalensis, possesses anticonvulsant property mediated by GABAergic neurons. Intraperitoneal injection of wogonin into rodents half hour before testing significantly prevented the convulsion stimulated by pentylenetetrazole and electroshock, decreased the electrogenic response score, and dose-dependently increased the influx of Cl- ions into the intracellular area. Since locomotor activities of wogonin-treated rodents did not change, as well as their endurance times on the rota rod, it seems that wogonin did not produce a sedative and myorelaxation effect. [18]

Anti-Alzheimer's: The findings of Song et al. (2009) confirmed the preventive benefits that Scutellaria baicalensis provides against memory impairment and neuronal injury in aged rats, suggesting its utility in managing senile dementia and delaying the aging process. Aged rats pretreated with Scutellaria baicalensis at doses of 35–140 mg/kg for 16–21 days manifested a noticeable improvement in cognitive function (as determined using the Morris water maze), neuropathological changes (as observed under light/electron microscope), and biochemical abnormalities. [19]

The flavonoids found in the stems and leaves of the Chinese skullcap appear to improve the capacity for learning and memory of experimental animals and to attenuate the pathologic changes in neurons that were induced by some reagents. They had been proven by Shang et al. (2006) to ameliorate memory deficits and reduce neuronal damage triggered by permanent cerebral ischemia in rats, signifying their promising usefulness in the treatment of cerebrovascular dementia. Orally provided at doses of 17.5–70 mg/kg for 20 days, the total flavonoids of Chinese skullcap significantly reduced the long latency time spent by ischemic rats to seek the hidden platform during the tests for learning and memory performance and increased the swimming time spent in the target quadrant in the Morris water maze. In this study, neuronal morphologic observations were carried out to determine the degree of damage in the neurons of the hippocampus and cerebral cortex. The results indicated an inhibition of ischemia-induced neuronal damage by the administered flavonoids. [20]

Antiviral: Baicalin isolated from the Chinese skullcap roots had also been revealed to prevent respiratory syncytial virus (RSV) infection and to diminish inflammatory cell infiltration and lung injury in mice owing to its antiviral and anti-inflammatory properties. Substantial damage to the lungs and a proinflammatory response, including CD4 and CD8 T lymphocyte infiltration, resulted from the RSV infection in mice. Baicalin treatment was observed to elicit an attenuation of T lymphocyte infiltration and gene expression of proinflammatory factors and to moderately reduce RSV titers in lung tissues. [21]

Skullcap - Contraindications, Interactions, And Safety

The American and Chinese skullcaps are regarded as generally safe to use, especially when taken at appropriate doses. To date, there have been limited data on their contraindications and interactions with drugs or other herbs. Because of the lack of reliable documented information on the safe use of these plants by pregnant and lactating women, their intake for medicinal purposes by this special population should be done with caution or is best avoided. In many herbal products, the American skullcap can sometimes be adulterated with germander (Teucrium canadense), which is potentially hepatotoxic because of its diterpene content. [4] Hence, one should obtain a skullcap product from a trustworthy source.

References:

[1] N. Joshee, T. S. Patrick, R. S. Mentreddy and A. K. Yadav, "Skullcap: Potential Medicinal Crop," in Trends in New Crops and New Uses, Alexandria, Virginia: ASHS Press, 2002, p. 580–586.

[2] X. Shang, X. He, M. Li, R. Zhang, et al., "The genus Scutellaria an ethnopharmacological and phytochemical review," Journal of Ethnopharmacology, vol. 128, no. 2, p. 279–313, 2010. https://www.ncbi.nlm.nih.gov/pubmed/20064593

[3] S. D. Ehrlich, "Skullcap," University of Maryland Medical Center (UMMC), 6 July 2014. https://www.umm.edu/health/medical/altmed/herb/skullcap

[4] L.-Z. Lin, J. M. Harnly and R. Upton, "Comparison of the phenolic component profiles of skullcap (Scutellaria lateriflora) and germander (Teucrium canadense and T. chamaedrys), a potentially hepatotoxic adulterant," Phytochemical Analysis, vol. 20, no. 4, p. 298–306, 2009. https://www.ncbi.nlm.nih.gov/pubmed/19402188

[5] "Scutellaria Linnaeus," Flora of China. https://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=129910

[6] C. Brock, J. Whitehouse, I. Tewfik and T. Towell, "American skullcap (Scutellaria lateriflora): a randomised, double-blind placebo-controlled crossover study of its effects on mood in healthy volunteers," Phytotherapy Research, vol. 28, no. 5, p. 692–698, 2014. https://www.ncbi.nlm.nih.gov/pubmed/23878109

[7] R. Awad, J. Arnason, V. Trudeau, et al., "Phytochemical and biological analysis of skullcap (Scutellaria lateriflora L.): a medicinal plant with anxiolytic properties," Phytomedicine, vol. 10, no. 8, p. 640–649, 2003. https://www.sciencedirect.com/science/article/pii/S0944711304702767

[8] Z. Zhang, X. Lian, S. Li and J. Stringer, "Characterization of chemical ingredients and anticonvulsant activity of American skullcap (Scutellaria lateriflora)," Phytomedicine, vol. 16, no. 5, p. 485–493, 2009. https://www.ncbi.nlm.nih.gov/pubmed/18786819

[9] Q. Zhao, X. Chen and C. Martin, "Scutellaria baicalensis, the golden herb from the garden of Chinese medicinal plants," Science Bulletin, vol. 61, no. 18, p. 1391–1398, 2016. https://www.ncbi.nlm.nih.gov/pubmed/27730005

[10] J. Han, M. Ye, M. Xu, et al., "Characterization of flavonoids in the traditional Chinese herbal medicine-Huangqin by liquid chromatography coupled with electrospray ionization mass spectrometry," Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences, vol. 848, no. 2, p. 355–362, 2007. https://www.ncbi.nlm.nih.gov/pubmed/17118721

[11] K. Song, S. Lee, B. Kim, A. Park and J. Kim, "Extracts of Scutellaria baicalensis reduced body weight and blood triglyceride in db/db mice," Phytotherapy Research, vol. 27, no. 2, p. 244–250, 2013. https://onlinelibrary.wiley.com/doi/10.1002/ptr.4691/full

[12] H. Bochoráková, H. Paulová, J. Slanina, P. Musil and E. Táborská, "Main flavonoids in the root of Scutellaria baicalensis cultivated in Europe and their comparative antiradical properties," Phytotherapy Research, vol. 17, no. 6, p. 640–644, 2003. https://www.ncbi.nlm.nih.gov/pubmed/12820232

[13] Z. Xu, F. Wang, S. Tsang, K. Ho, et al., "Anxiolytic-like effect of baicalin and its additivity with other anxiolytics," Planta Medica, vol. 72, no. 2, p. 189–192, 2006. https://www.ncbi.nlm.nih.gov/pubmed/16491459

[14] B. Króliczewska, D. Miśta, W. Zawadzki, A. Wypchło and J. Króliczewski, "Effects of a skullcap root supplement on haematology, serum parameters and antioxidant enzymes in rabbits on a high-cholesterol diet," Journal of Animal Physiology and Animal Nutrition, vol. 95, no. 1, p. 114–124, 2011. https://www.ncbi.nlm.nih.gov/pubmed/20666864

[15] F. Ye, L. Xui, J. Yi, W. Zhang and D. Zhang, "Anticancer activity of Scutellaria baicalensis and its potential mechanism," Journal of Alternative and Complementary Medicine, vol. 8, no. 5, p. 567–572, 2002. https://www.ncbi.nlm.nih.gov/pubmed/12470437

[16] F. Ye, Y. Che, E. McMillen, J. Gorski, D. Brodman, et al., "The effect of Scutellaria baicalensis on the signaling network in hepatocellular carcinoma cells," Nutrition and Cancer, vol. 61, no. 4, p. 530–537, 2009. https://www.ncbi.nlm.nih.gov/pubmed/19838925

[17] H. Jung, M. Kim, N. Gwak, et al., "Antiallergic effects of Scutellaria baicalensis on inflammation in vivo and in vitro," Journal of Ethnopharmacology, vol. 141, no. 1, p. 345–349, 2012. https://www.ncbi.nlm.nih.gov/pubmed/22414480

[18] H. Park, S. Yoon, J. Choi, et al., "Anticonvulsant effect of wogonin isolated from Scutellaria baicalensis," European Journal of Pharmacology, vol. 574, no. 2–3, p. 112–119, 2007. https://www.ncbi.nlm.nih.gov/pubmed/17692312

[19] H. Song, J. Cheng, H. Miao and Y. Shang, "Scutellaria flavonoid supplementation reverses ageing-related cognitive impairment and neuronal changes in aged rats," Brain Injury, vol. 23, no. 2, p. 146–153, 2009. https://www.ncbi.nlm.nih.gov/pubmed/19191093

[20] Y. Shang, H. Miao, J. Cheng and J. Qi, "Effects of amelioration of total flavonoids from stems and leaves of Scutellaria baicalensis Georgi on cognitive deficits, neuronal damage and free radicals disorder induced by cerebral ischemia in rats," Biological and Pharmaceutical Bulletin, vol. 29, no. 4, p. 805–810, 2006. https://www.ncbi.nlm.nih.gov/pubmed/16595923

[21] H. Shi, K. Ren, W. Zhang, Y. Zhao, et al., "Baicalin from Scutellaria baicalensis blocks respiratory syncytial virus (RSV) infection and reduces inflammatory cell infiltration and lung injury in mice," Scientific Reports, p. 35851, 2016. https://www.ncbi.nlm.nih.gov/pubmed/27767097

Article researched and created by Dan Ablir for herbshealthhappiness.com.
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