Sophora species: Mescal

Family

Fabaceae

Common Names

Mescal bean, Texas mountain laurel, Coral bean (Sophora secundiflora)

Japanese pagoda tree (S. japonica)

Kowhai (S. tetraptera)

Silky sophora, white sophora (S. nuttalliana)

Plant Description

The genus Sophora comprises some 70 species found mainly in the northern hemisphere. Occurring as forbs, shrubs, or trees, these perennials can be deciduous or evergreen. Leaves are typically compound, with 5 - 60 leaflets, a terminal leaflet being present. Inflorescences are terminal racemes or panicles. Sepals are fused with short lobes and the five petals are pea-like, with the banner ovate or obovate, erect or reflexed, the wing petals oblique-oblong, keels rounded or accuminate, enclosing the 10 stamens. Flower colors include white, yellow, and blue-purple (Fig. 371 and Fig. 372). The seeds are produced in legume ponds that are distinctively constricted between the seeds, leathery or woody, and either indehiscent or dehiscent (Fig. 373). The few or many seeds are often yellow or red in color, waxy, hard-coated, and oblong or kidney shaped (Fig. 374).

Figure 371. Sophora secundiflora.

Figure 372. Sophora secundiflora flowers.

Figure 373. Sophora secundiflora pods.

Figure 374. Sophora secundiflora beans.

Toxic Principle and Mechanism of Action

Sophora species contain a wide variety of biologically active quinolizidine alkaloids that are generally grouped according to their similarity to the alkaloids cytisine, sparteine, and matrine [1]. Cytisine, being one of the most toxic alkaloids, has nicotinic effects on the ganglia, initially stimulating and then blocking conduction [2,3]. The alkaloids cause ataxia, excessive salivation, increased heart rate, and seizures. Cardiac arrhythmias may develop when large quantities of the alkaloids are consumed. Some of the alkaloids present in Sophora species have hallucinogenic properties similar to that of mescaline [4]. The bark of some species (S. japonica) contain toxic lectins similar to those found in the bark of the black locust (Robinia pseudoacacia).

Risk Assessment

Some species of Sophora are commonly grown as garden plants, and are rarely a problem to household pets. Cattle, sheep, and goats that browse on the plants are more commonly intoxicated. However, some species of Sophora produce large quantities of seed (S. secundiflora) and the attractive red waxy beans may be an attraction to pets and children who may ingest them (Fig. 374).

Clinical Signs

The nature and severity of clinical signs expected in Sophora poisoning depends on the species and the amount of plant ingested. Cattle poisoned by Sophora secundiflora develop neurologic signs including stiffness of the hindlegs, muscle tremors, and an inability to rise [5]. Similar neurologic signs of muscle rigidity, exercise intolerance, and collapse on being forced to exercise can be anticipated in dogs and other animals consuming the seeds [6].