Epimedium
brevicornu Maxim., E.
grandiflorum Morr., E. koreanum Nakai, E. pubescens Maxim., E.
sagittatum (Sieb. & Zucc.) Maxim., E. wushanense T. S. Ying
Standardized Common
Name: Epimedium
Other Common Names: Horny Goat Weed,
Yinyanghuo
Family: Berberidaceae
Taxonomy: Epimedium includes about 54 species in the most recent complete
treatment, although new Chinese species continue to be described with some
frequency. These are divided into two subgenera: Subg. Rhizophyllum has only two species, while Subg. Epimedium comprises five sections. The genus is endemic to Eurasia,
except for Subg. Rhizophyllum, which
extends into North Africa; the major center of diversity is in China.
Epimedium
sagittatum and E. grandiflorum
(which is found primarily in Japan and Northern Korea, as well as Manchuria)
are the species most commonly found on the North American market, where they
are frequently sold under the name Horny Goat Weed. In Chinese practice, all of
the above-listed species except E.
grandiflorum are sold interchangeably as Yinyanghuo; according to Herbs of Commerce, all six may be sold
as Epimedium. These species do not form a natural group: E. grandiflorum and E.
koreanum are placed within Sect. Macroceras,
while the other four species belong to Sect. Diphyllum. Epimedium koreanum
is very doubtfully distinguished from E.
sempervirens Nakai ex F. Maek., and both are treated by some authorities as
subspecies of E. grandiflorum. Epimedium brevicornu is incorrectly
rendered as “brevicornum” by many
sources.
Description: Rhizomatous
perennial herbs to 0.6(–1) m tall. Leaves mostly basal, with 1 or 2 or rarely 3
leaves on flowering stem (if >1, leaves opposite or whorled); leaves
1–2(–4)-ternately compound, stipulate with stipules forming a ligulate sheath
on basal leaves, reduced in size on stem leaves; leaflets at least a few cm
long, with spiny margins; bases of lateral leaflets usually more or less
oblique or asymmetrical. Inflorescence usually a loose, erect, many-flowered
panicle. Flower size varies greatly among species; sepals 8 in two whorls, the
inner whorl petaloid; petals 4, often spurred or reduced in size; stamens 4;
ovary 1. Fruit a 2-valved capsule; seeds few, arillate.
Parts
in Commerce:
Leaves (harvested at leaf maturity, after flowering)
Identification: All species have
ternately compound leaves; E. sagittatum,
E. wushanense and E. pubescens have usually trifoliolate
leaves (rarely reduced to one leaflet in basal leaves), while the other species
used have mostly biternate or occasionally more finely divided leaves. Since
leaflets will probably be separated from petioles and broken or cut in drying,
this character will be of limited use as a diagnostic feature for commercial
material. Leaflets are always well separated from each other on fairly long
petiolules. A few characters are common among these species:
- Leaf apex
usually more or less acuminate, sometimes acute
- Bases of central
leaflets more or less cordate; bases of lateral leaflets slightly to
greatly asymmetrical; lobes never overlap
- Margins always
bearing small spines, usually minutely toothed with the spines tipping the
teeth
- Venation
palmate, with the midrib strongest; main veins from base usually 7 in
central leaflets, (5–)6–8(–10) in lateral leaflets; higher order venation
reticulating, even very small veins observable on both surfaces
- Lower surface
usually lighter in color, often appearing somewhat waxy
- Taste slightly
bitter
However,
the official species vary in other characteristics:
E. brevicornu
- Leaflets ovate
to suborbicular, (2–)3–8 cm long
- Apex acute to
short-acuminate
- Base of central
leaflets cordate; lateral leaflets slightly asymmetrical, the larger lobe
rounded or sometimes pointed
- Texture fairly
thick at maturity
- Lower surface
grayish green, sparsely pubescent at base of main veins
E. grandiflorum
- Leaves narrowly
to broadly ovate, 3–13 cm long
- Base of central
leaflets deeply cordate; lateral leaflets somewhat asymmetrical, both
lobes rounded or rarely outer lobe pointed
- Texture thin
- Lower surface
glabrous or sparsely pubescent especially around petiole attachment and
midrib; hairs thin, sometimes brownish or with brown bands of pigment
E. koreanum
- Leaves narrowly
to broadly ovate, 4–10 cm long
- Base of central
leaflets usually deeply cordate with a narrow cleft between lobes; lateral
leaflets very asymmetrical, the larger lobe pointed or sometimes rounded
- Texture thin or
leathery
- Lower surface
glabrous and waxy or bearing small appressed hairs
E. pubescens
- Leaflets ovate
to lanceolate, 3–15 cm long
- Base of central
leaflets cordate; lateral leaflets very asymmetrical, the larger lobe
usually rounded, rarely acute-pointed
- Texture leathery
- Lower surface
usually pubescent with soft gray hair, especially around base of main
veins and petiole attachment
E. sagittatum
- Leaflets
lanceolate to narrowly ovate, 4–12(–19) cm long
- Base of central
leaflets cordate to sagittate (similar to cordate but with pointed lobes);
lateral leaflets very asymmetrical with large pointed or sometimes rounded
outer lobe, small rounded inner lobe
- Texture leathery
- Lower surface
glabrous or bearing minute single-celled appressed hairs
E. wushanense
- Leaflets
lanceolate to narrowly lanceolate, 7–13(–23) cm long
- Base of central
leaflets shallowly cordate; lateral leaflets very asymmetrical with outer
lobe usually long and pointed
- Texture leathery
- Lower surface
glabrous or densely pubescent with erect hairs
Adulterants: A number of other
species are native to the same geographical region, so accidental substitution
is a possibility, although it is not reported to be a problem. The popular
species are frequently cultivated, and some of the other species are very rare
or of limited distribution; these facts reduce the likelihood of confusion.
Many species can be distinguished from the official six by differing leaf
morphology. However, given the considerable variation within as well as among
species, it is impossible to reliably identify material to the species level
without flowers. The possible inclusion of similar species therefore cannot be
completely ruled out by morphological examination. In-depth chemical surveys of
Epimedium would be desirable; if
fixed chemical differences justifying the preference for the official six
species were discovered, a chemical method of identifying those species would
simultaneously be made available.
References:
Ohwi J. Flora
of Japan (in English). Washington, DC: Smithsonian Institution; 1965.
Pharmacopoeia Commission
of PRC, eds. Pharmacopoeia of the People’s Republic of China, English ed., vol. 1. Beijing: Chemical
Industry Press; 1997:93–94.
Stearn WT. Epimedium
dolichostemon (Berberidaceae) and other Chinese species of Epimedium. Kew Bull. 1990;45:685–692.
Stearn WT. The
Genus Epimedium and Other Herbaceous
Berberidaceae. Portland, OR: Timber Press; 2002.
Figure 24: a–b, Epimedium sagittatum, lateral leaflet
and close-up of lower surface; c, E.
grandiflorum, central leaflet.