Medicinal plants still comprise a nebulous cloud in biomedical science. We know they have been used since the dawn of man, but there are precious few good quality scientific studies that support their use. Unlike pharmaceutical drugs, plant medicines consist of many different molecules that interact together in the body to have a variety of, poorly understood, pharmacological effects. Despite variably successful attempts to identify single molecules in plants for drug development, we should acknowledge that the whole is greater than a single part. There is an increasing number of clinical studies which strongly imply that root, leaf, and flower extracts of medicinal plants can influence the brain and are effective at treating cognitive disorders. This article series will examine plants where we have double-blind, placebo-controlled studies to support their medicinal influence on the human brain.

St. John’s wort is a commonly known plant that is native to Europe and yields bright yellow flowers. Its name comes from flowering around St. John’s day on the 24th June. St. John’s wort has been used as long ago as the ancient Greeks, and the physician Dioscorides (40–90AD) used it in the treatment of sciatica. However, St. John’s wort has become known as less of a treatment for nerve pain and more so for depression, with multiple double-blind, placebo-controlled trials confirming its antidepressant properties. Authors typically compare St. John’s wort with mainstream anti-depressant drugs and find it has a preferable side effects profile. It is not without its downsides however, as excessive use has been linked to serotonin syndrome, sun sensitivity, and easy skin burning, and more generally with increased pharmaceutical drug metabolism by the liver. This means St. John’s wort may not be suitable for applications alongside other pharmaceutical drugs, and it is contraindicated with serotonin reuptake inhibitors.

American skullcap is a member of the mint family that is native to North America and grows wild in meadows and swamps. It was used by the Native Americans as a sedative and America’s 19^th century physicians, the Eclectics, widely used the herb for complaints involving an overactive nervous system such as insomnia, anxiety, and epilepsy. A human double-blind, placebo-controlled study supports skullcap’s application against anxiety, and a mood elevating effect has also been noted. Herbalist’s view both St. John’s wort and American skullcap as ‘nervine tonics’, meaning that they act upon the nervous system medicinally and are also considered to have a long-term renewing effect. While, this claim is yet to be verified by scientific studies, it certainly warrants further investigation.

Ashwagandha, the root of which is a popular home remedy in India, is a plant native to India that is mentioned in the traditional Ayurvedic medical text, the Charaka Samhita, approximately 2000 years ago. Here it is recommended as a tonic for emancipation, reproductive ability, and longevity. In Ayurveda, it is classified as a ‘rasayana herb’, a class of plant that are considered to restore and support long-term health and that overlaps to some degree with the Western definition of a ‘tonic herb’. Two double-blind, placebo-controlled human studies support ashwagandha’s role in the reduction of anxiety. It’s wide-ranging medicinal properties are supported by two additional well-controlled, human clinical studies on osteoarthritis and subclinical hypothyroidism. The emerging picture is that ashwagandha possesses a wide range of medicinal properties that will likely be better understood in the future. Ashwagandha has been well-tolerated across clinical trials, with a side effect profile similar to placebo.

References

Auddy B, Hazra J, Mitra A, Abedon B, and Ghosal S. A standardized Withania somnifera extract significantly reduces stress-related parameters in chronically stressed humans: A double-blind, randomized, placebo-controlled study. J Am Nutraceutical Assoc. 2008;11:50–6. Access here.

Brock C, Whitehouse J, Tewfik I, and Towell T. (2014). American Skullcap (Scutellaria lateriflora): A Randomised, Double-Blind Placebo-Controlled Crossover Study of its Effects on Mood in Healthy Volunteers. Phytotherapy Research, 28(5), 692-698. DOI: 10.1002/ptr.5044

Castleman, Michael. “The new healing herbs.” Bantam Book, New York (2001): 465-471. ISBN: 1605298891

Chandrasekhar K, Kapoor J, and Anishetty S. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian Journal of Psychological Medicine 34.3 (2012): 255. DOI: 10.4103/0253-7176.106022

Dannawi M. Possible serotonin syndrome after combination of buspirone and St John’s Wort. Journal of Psychopharmacology 16.4 (2002): 401-401. DOI: 10.1177/026988110201600420

Hoffman, David. Holistic herbal. Element Books, 1988. ISBN: 1852300248

Laakmann G, Schüle C, Baghai T, and Kieser M. St. John’s wort in mild to moderate depression: the relevance of hyperforin for the clinical efficacy. Pharmacopsychiatry 31.S 1 (1998): 54-59. DOI: 10.1055/s-2007-979346

Markowitz JS, Donovan JL, DeVane CL, Taylor RM, Ruan Y, Wang JS, and Chavin KD. Effect of St John’s wort on drug metabolism by induction of cytochrome P450 3A4 enzyme. Jama 290.11 (2003): 1500-1504. DOI: 10.1001/jama.290.11.1500

Ramakanth GS, Uday Kumar C, Kishan PV, and Usharani P. A randomized, double blind placebo controlled study of efficacy and tolerability of Withaina somnifera extracts in knee joint pain. Journal of Ayurveda and integrative medicine 7.3 (2016): 151-157. DOI: 10.1016/j.jaim.2016.05.003

Scudder, John. Specific Medication and Specific Medicines, 1870. ISBN:

Sharma AK, Basu I, and Singh S1. Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial. The Journal of Alternative and Complementary Medicine (2017). DOI: 10.1089/acm.2017.0183

Szegedi A, Kohnen R, Dienel A, and Kieser M. Acute treatment of moderate to severe depression with hypericum extract WS 5570 (St John’s wort): randomised controlled double blind non-inferiority trial versus paroxetine. Bmj 330.7490 (2005): 503. DOI: 10.1136/bmj.38356.655266.82

Woelk, Helmut. Comparison of St John’s wort and imipramine for treating depression: randomised controlled trial. Bmj 321.7260 (2000): 536-539. PMCID: PMC27467

Wolfson P and Hoffmann DL. An investigation into the efficacy of Scutellaria lateriflora in healthy volunteers. Alternative therapies in health and medicine 9.2 (2003): 74. PMID: 12652886

Image via kerdkanno/Pixabay.