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By Michael Barr, MSc, LAc, Dipl OM and

Susanne Thomas, PhD

Michael Barr, MSc, LAc, Dipl OM, a recovering logician

and cheerful polemicist, attended Samra University and

Dongguk University in Los Angeles before completing

his Chinese medicine education at Pacific College of

Oriental Medicine in New York, where he is part of a multi-

disciplinary group practice.

Susanne Thomas, PhD, is the Associate Editor of The

American Acupuncturist. She is an ardent researcher and

an advocate of herbal medicine.

Biological Profile

A member of the poppy family (Papaveraceae), Corydalis yanhusuo1 has been used for centuries in traditional Chinese medicine (TCM) as an analgesic (1, 2). The root of C. yanhusuo (Corydalis tuber rhizome, or CTR) can be used medically by processing it to extract the alkaloidal components dehydrocorybulbine (DHCB) and l-tetrahydrocoptisine (l-THP) as well as a number of other useful alkaloids (2,3,4). While the DHCB pain-relieving mechanism of action is related to the alkaloid’s anti-inflammatory properties, I-THP has been demonstrated to bind to dopamine receptors (5) and may be more effective in treating neuropathic pain (6). Interestingly, when E Zhu (Rhizoma Curcumae) is used in combination with Yan Hu Suo (Rhizoma Corydalis) in a ratio of 3:2 (E Zhu to Yan Hu Suo, referred to as E3Y2), these herbal extracts have been demonstrated to exhibit a strong anti-tumor effect (7).

An early study by Yuan et al., published in 2004 in the Journal of Clinical Pharmacology, evaluated the pain-relieving effects of C. yanhusuo in tandem with Bai Zhi (Angelica Root /Radix Angelicae dahuricae) (8). Employing the commonly-used cold-pressor test, the scientists observed significantly reduced scores in both pain intensity and incommodity in human subjects (P <.01) as well as a dose-related analgesic effect and concluded that extracts of the two herbs may have “potential value for treating mild to moderate pain”

Pain-Relieving Effects of Corydalis (Yan Hu Suo/ Rhizoma Corydalis)

Corydalis (Greek korydalís “crested lark”)

1. The original name for the herb commonly known as Yan Hu Suo is Xuan Hu Suo, or “dark barbarian rope.” The name was changed during the reign of Xuan Ye, an emperor during the early Qing dynasty. During this time the characters of his name, xuan and ye, were taboo and could not be used for any other purpose. Xuan was changed to Yan in the herb name, and Yan Hu Suo has remained the most commonly used name for the herb, though occasionally the original name may be referred to.

20 T h e A m e r i c a n A c u p u n c t u r i s t Summer 2015

(8). However, it was not until a seminal study on CTR by Zhang et al., was published in January of 2014 in Current Biology (2), that the biomedical community and the larger popular medical press took note of the potent analgesic effect of this Chinese herb. In rapid succession, articles explaining the discovery of Zhang et al. were published in The Los Angeles Times, (9) Medical Daily (10), the online University Herald (11), and other publica-tions including university newspapers, health magazines, and various TCM websites.

The study by Zhang et al. was part of the ongoing, ambitious “herbalome” project targeting the discovery of “new endogenous transmitters and hormones” (2) and creating a compendium of “all the compounds in plant extracts that display pharmaco-logical properties” (12). The scientific team studied ten TCM plant extracts. Using a “reverse pharmacology approach” (2) developed by Olivier Civelli, PhD, chair of the Department of Pharmacology at the University of California School of Medicine at Irvine (12) on dopamine receptor knockout mice, Zhang et al. demonstrated that the “DHCB antinociceptive effect is primarily due to its interaction with D2 receptors, at least at low doses. [They] further show that DHCB is effective against inflamma-tory pain and injury-induced neuropathic pain, and furthermore causes no antinociceptive tolerance” (2). Given the benign profile of DHCB and its potential to supplement or even replace tolerance-inducing traditional pharmacological analgesics, the findings of Zhang et al. represent powerful evidence-based support for TCM applications of Corydalis.

Geography and CultivationThis flowering perennial is cultivated widely in central Eastern China, Japan, and Siberia (13), has been used as an analgesic for centuries, and continues to be used today by TCM practitioners. The genus Corydalis comprises over 300 species of plants indigenous to many different parts of the world, most of which are known for their pain-relieving effects and many of which are cultivated in gardens for their pretty flowers and foliage. There are several species which are acceptable for use in Chinese medicine, including C. turtschaninovii, C. repens, and C. ambigua var. amurensis (14).

Harvesting and PreparationFor medicinal use, good-quality Yan Hu Suo are dried tubers that are light yellow, hard, and large. They are cut into slices, showing a glossy, wax-like cross section. Small rhizomes with a grayish yellow cross section are considered poor quality (14). The plant tuber is harvested from April through June after the flowers have died or dropped off. The tuber is then dried and stored for later use. The plant prospers in soil that is well-drained but moist, and adapts

to both sandy and loamy environments with acidic, neutral, and alkaline pH. C. yanhusuo can grow in either semi-shade or no shade (15).

Chronic-Pain Applications In TCM, Corydalis is reported to invigorate the blood, promote the movement of qi, and alleviate various types of pain, such as abdominal, menstrual, musculoskeletal, and arthritic pain (15,16).

DosageChen and Chen advise using “3 to 10 grams in decoction with maximum dose of 20 grams. Use 1 to 1.5 grams of powdered yan hu suo served in warm water [as a tea]... Frying it with vinegar enhances the analgesic function” (16). When prepared as a tea, honey may be used to render the plant’s bitter taste more tolerable to the palate, although purists might insist the bitterness is essential to its effect. Prepared liquid extracts are also available and should be taken according to label directions. Corydalis is also taken in combination with white peony (Bai Shao/Radix Peoniae lactiflorae), cramp bark (Cortex Viburnum opulus), and valerian root (Radix Valeriana oficinalis) for pain relief for menstrual cramping and numerous other conditions (6,11,16). TCM formulas include two of the “Zhu Yu” formulas, Ge Xia and Shao Fu, as well as several lesser-known formulas, such as the eponymous Yan Hu Suo Tang itself and a four-ingredient Zhu Danxi formula called Shou Nian San or “Pinch Powder.”

Contraindications/interactionsCorydalis is not recommended for pregnant or nursing women and is to be taken with caution or dose-adjusted for individuals with impaired hepatic function or kidney disease (15). For optimal outcomes, Corydalis is used most effectively by certified practitio-ners who are familiar with all cautions and contraindications (16).

“ The genus Corydalis comprises over 300 species of plants indigenous to many different parts of the world, most of which are known for their pain-relieving effects and many of which are cultivated in gardens for their pretty flowers and foliage.”

Pain-Relieving Effects of Corydalis (Yan Hu Suo/Rhizoma Corydalis)

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References1. Ding GS. Important Chinese herbal remedies. Clin Ther. 1987 [cited 2015 Jul

20];9(4):345-57. In: PubMed [Internet]. Bethesda (MD): National Library of Medicine (US). [1950] - . [about 1 screen]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/?term=important+chinese+herbal+remedies+clin+ther PMID:3607815.

2. Zhang Y, Wang C, Wang L, Parks GS, Zhang X, Guo Z, Ke Y, Li KW, Kim MK, Vo B, Borrelli E, Ge G, Yang L, Wang Z, Garcia-Fuster MJ, Luo ZD, Liang X, Civelli O. A novel analgesic isolated from a traditional Chinese medicine. Curr Biol [Internet]. 2014 Jan 20 [cited 2015 Jul 20];24(2):117-23. Available from: http://www.cell.com/current-biology/abstract/S0960-9822(13)01494-2

3. Dharmananda S. Simple traditional formulas for pain: shixiao san, jin lingzi san, liang fu wan, and baishao gancao tang [Internet]. Portland (OR): Institute for Traditional Medicine; 2002 Aug [cited 2015 Jul 28]. Available from: http://www.itmonline.org/arts/pain.htm

4. Choi JG, Kang SY, Kim JM, Roh DH, Yoon SY, Park JB, Lee JH, Kim HW. Antinociceptive effect of Cyperi rhizoma and Corydalis tuber extracts on neuro-pathic pain in rats. Korean J Physiol Pharmacol [Internet]. 2012 Dec 10 [cited 2015 Jul 28];16(6):387-92. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3526742/

5. Ingram SL. Pain: novel analgesics from traditional Chinese medicines. Curr Biol [Internet]. 2014 Feb 3 [cited 2015 Jul 20];24(3):R114–R116. Available from: http://www.sciencedirect.com/science/article/pii/S0960982213015893

6. Health System: University of Michigan [Internet]. Ann Arbor (MI): Regents of the University of Michigan; c1995-2015. Corydalis; c2014 [reviewed 2014 Apr 15; cited 2015 Jul 20]; [about 7 screens]. Available from: http://www.uofmhealth.org/health-library/hn-2074006

7. Gao JL, He TC, Li YB, Wang YT. A traditional Chinese medicine formulation con-sisting of Rhizoma Corydalis and Rhizoma Curcumae exerts synergistic anti-tumor activity. Oncol Rep [Internet]. 2009 Nov 1 [cited 2015 Jul 20];22(5):1077-83. Available from: http://www.spandidos-publications.com/or/22/5/1077

8. Yuan CS, Mehendale SR, Wang CZ, Aung HH, Jiang T, Guan X, Shoyama Y. Effects of Corydalis yanhusuo and Angelicae dahuricae on cold pressor-induced pain in humans: a controlled trial. J Clin Pharmacol [Internet]. 2004 Nov [cited 2015 Jul 20];44(11):1323-7. Available from: http://onlinelibrary.wiley.com/doi/10.1177/0091270004267809/full

9. Netburn D. Study finds a potent painkiller in traditional Chinese medicine [Internet]. Los Angeles Times. 2014 Jan 2 [cited 2015 Jul 20]; Medicine: [about 2 screens]. Available from: http://articles.latimes.com/2014/jan/02/science/la-sci-sn-chinese-medicine-chronic-pain-20140102

10. Ericson J. Chinese poppy plant, corydalis, works for chronic pain [Internet]. Medical Daily. 2014 Jan 2 [cited 2015 Jul 20]; Drugs: [about 4 screens]. Available from: http://www.medicaldaily.com/chinese-poppy-plant-corydalis-works-chronic-pain-266215

11. Chinese herbal compound effective in reducing chronic pain, study [Internet]. University Herald. 2014 Jan 4 [cited 2015 Jul 14]: [about 3 screens]. Available from: http://www.universityherald.com/articles/6601/20140104/chinese-herbal-compound-chronic-pain-dehydrocorybulbine-dhcb-corydalis-yanhusuo.htm

12. Chia J. The plant that could erase chronic pain: an ancient Chinese remedy shows promise [Internet]. Prevention. 2014 Jan 2 [cited 2015 Jul 20]; Health: [about 3 screens]. Available from: http://www.prevention.com/health/health-concerns/chinese-remedy-corydalis-pain

13. Holloway A. Ancient Chinese herbal remedy may be solution for chronic pain [Internet]. Ancient Origins. 2014 Jan 4 [cited 2015 Jul 20]; News: [about 3 screens]. Available from: http://www.ancient-origins.net/news-history-archaeology/ancient-chinese-herbal-remedy-may-be-solution-chronic-pain-001197

14. Bensky D, Gamble A, Clavey S, Stoger E. Chinese herbal medicine materia medica. 3rd ed. Seattle: Eastland Press;2004.

15. Wang WT. Corydalis yanhusuo. [cited 2015 Jul 21]. In: Plants for a Future [Internet]. Dawlish (England): Plants for a Future. c1996-2012. [about 5 screens]. Available from: http://www.pfaf.org/user/Plant.aspx?LatinName=Corydalis+yanhusuo

16. Chen J, Chen T. Chinese medical herbology and pharmacology of Chinese herbs. Industry (CA): Art of Medicine Press; 2004.

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