1. v 71 The American Acupuncturist 19
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.

2. 20 The American Acupuncturist 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 Cultivation
This 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 Preparation
For 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).
Dosage
Chen 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/interactions
Corydalis 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)

3. v 71 The American Acupuncturist 21
References
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