Rhamnus species: Buck thorn

Family

Rhamnaceae

Common Name

Buckthorn

Common species include R. californica (California buckthorn, coffee berry, pigeon berry), R. caroliniana (Carolina buckthorn, Indian cherry), R. cathartica (common buckthorn), R. frangula (alder buckthorn).

Plant Description

A genus of about 125 species of deciduous or evergreen usually thorny shrubs to small trees, Rhamnus are native to many temperate regions of the world. Erect, branching, 1 - 10m tall shrubs or trees, with alternate, petiolate, ovate to oblong leaves, some variegated.

Inflorescences are umbels or solitary flowers produced in leaf axils. Flowers are small, greenish to yellow-white, sepals 4 - 5, triangular, petals 4 - 5 or absent. Fruits are berry-like drupes that can be brown, orange, or black in color (Fig. 336).

A shrub or small tree native to southwestern North America commonly referred to as buckthorn, coyotillo and wild cherry to mention but a few of many common names is Karwinskia humboldtiana. The ripe fruits are edible but the seeds and foliage are poisonous to people and animals. Toxic anthracenones in the seeds cause degeneration of the peripheral nerves [1]. Karwinskia is rarely grown as an ornamental and is more of a problem to livestock browsing on the plants in arid areas and to children who may eat the unripe fruits and seeds [2].

Figure 336. Rhamnus cathartica.

Toxic Principle and Mechanism of Action

The purgative action is due to anthrones and anthraquinones in the fruits and to a much lesser extent in the leaves [3]. Rhamnus purschiana is the origin of cascara sagrada, a well known cathartic.

Risk Assessment

Buckthorns are commonly grown for their attractive leaves, blossoms that attract bees, and for their fruits. Consequently children and pets have the potential for poisoning from the berries. The leaves are minimally toxic if eaten in very large quantities.

Clinical Signs

Vomiting, abdominal pain, and diarrhea that can become hemorrhagic can be expected [2]. In severe cases dehydration may result and will require fluid therapy. Activated charcoal and other adsorbents should be given orally.