Rhamnus
cathartica L.
Standardized Common
Name: Buckthorn
Family: Rhamnaceae
Taxonomy: Rhamnus
includes over 100 species of trees and shrubs, of which about a dozen are
native to Europe. This group has been divided into two genera, Rhamnus
and Frangula (e.g., Frangula purshiana Cooper, Cascara
Sagrada), in most recent floristic treatments. Species boundaries are
occasionally difficult, and modern taxonomic work is somewhat limited. Rhamnus
cathartica ranges from Europe to western China and has been naturalized in
the eastern United States. It is known to hybridize with other species.
Description: Shrub to 6 m high or
small tree. Twigs greyish, often tipped with a small needlelike thorn. Leaves
mostly opposite or subopposite,
stipulate with stipules falling early, petiolate, elliptical to ovate or
oblong-elliptic, 2–8(–10) cm long, glabrous to pubescent; base cuneate to
rounded or subcordate; apex obtuse to somewhat acuminate; margins crenate;
venation pinnate, with 2–5 pairs of arcuate secondary veins, conspicuous
beneath. Inflorescences lateral, cymose. Flowers small, mostly unisexual,
occasionally bisexual; sepals 4, basally fused; nectar disk present inside
calyx; petals 4; stamens 4, opposite petals rather than alternating with them;
ovary 4-loculed, with 1 ovule per locule. Fruit a drupe, berry-like, 6–8 mm in
diameter, black at maturity, with 3–4 pyrenes.
Parts
in Commerce:
Fruit
Identification:
- Nearly
spherical, (4–)6–8(–9) mm long
- Juicy when fresh
- Pedicel 5–10 mm
long, longitudinally wrinkled
- Circular
attachment of pedicel with a raised ring-shaped, sometimes pale edge
- Fruit surface
blackish to blackish-red, glabrous, wrinkled when dry
- Flesh
greenish-yellow; most of fruit volume occupied by mature pyrenes (“seeds”)
- Pyrenes (3–)4
per fruit, not 2
- Pyrenes dark
brown to greenish, plump, roughly triangular in cross-section with two
flattened sides and one rounded side, or irregularly rounded with a single
narrow longitudinal ridge along one side
- Taste initially
sweet, then bitter and nauseating; colors saliva reddish
Adulterants: Frangula alnus
Mill. (Frangula, also known as Rhamnus frangula L.) is a reported
adulterant. The fruit becomes blackish at maturity, but may be distinctly red
rather than blackish red. The seeds are laterally compressed or flattened, with
the maximum breadth almost equalling the length; the shape is somewhat
triangular-ovate, with a blunt apex. The narrow end of the seed bears two
yellowish to orangish, slightly asymmetrical projections, separated by a
shallow cleft.
References:
Browicz K, Zieliński J. Rhamnaceae. Rechinger KH,
ed. Flora Iranica, vol. 125. Graz, Austria: Akademische Druck- u.
Verlagsanstalt; 1977.
Davis PH, Yaltirik F. Rhamnus. In: Davis PH,
ed. Flora of Turkey and the East Aegean Islands, vol. 2.
Edinburgh: Edinburgh University Press; 1967:526–541.
Fernald ML. Gray’s Manual of Botany, 8th ed. New York: American Book
Company; 1950:992–993.
Gil-ad NL, Reznicek AA. Evidence of hybridization of
two Old World Rhamnus species—R. cathartica and R. utilis
(Rhamnaceae)—in the New World. Rhodora. 1997;99:1–22.
Tutin TG. Rhamnus. In: Tutin TG, Heywood VH, Burges NA, et al.,
eds. Flora Europaea. Vol. 2. Cambridge: Cambridge University
Press; 1968:244–245.
Youngken HW. Text-Book of Pharmacognosy, 5th ed. Philadelphia, PA: The
Blakiston Company; 1943:560–561.
Figure 59: a–b, Rhamnus cathartica infructescence and
pyrene.