Medicinal Araliaceae

The traditional systems of medicine of Asia and the Pacific use about 50 species of plant species classified within the family Araliaceae that are of medicinal value and notably used as tonic. Examples od such plants are of Panax ginseng C. A. Meyer (ginseng), Panax notoginseng Burk. (san chi ginseng), Panax japonicus C. A. Meyer (Japanese ginseng), and Acanthopanax senticosus (Siberian ginseng). The evidence for the existence of immunostimulating and anabolic saponins in Panax and Acanthopanax species is strong and well documented, but much less work has been done with the dopami-nergic potentials of these saponins.

Acanthopanax gracilistylus W. W. Sm. (Acanthopanax spinosus Miq, Eleutherococcus gracilistylus), or wu chia (Chinese), gokahi (Japanese), or ogap'i (Korean), is a deciduous shrub growing to 3 m wild in East Asia and China. The leaves are palmatilobed and show five folioles that are elliptic lanceolate, fleshy, and serrate. The influorescence consists of small umbels up to 6 cm long. The drug consists of the root bark found in Chinese pharmacies in the form of yellowish-brown pieces; it is used for rheumatism, general debility, impotency, and muscular pains. In Malaysia, the plant is used as carminative.

Fujikawa et al. made the interesting observation that an extract from the stem bark given orally at a dose of 250 mg/kg once a day for 2 weeks protects rats against MPTP-induced Parkinsonian bradykinesia and catalepsy and inhibited neuronal loss of dopamine (70). The active constituents involved here are unknown. Note that the plant abounds with pentacyclic oleanene saponins (71-73). Note that Acanthopanax species are known to elaborate a series of diterpenes, a group that has the potency to bind to dopamine receptors, as reported in Vitex agnus-castus. Are diterpenes involved in the dopaminergic properties of Acanthopanax gracilistylus W. W. Sm.?

There is an expanding body of evidence to suggest that ginsenosides have a protective effect on the dopaminergic system. Radad et al. made a careful study on the effects of ginsenosides Rb1 and Rg1 on dopaminergic neurones from embryonic mouse mesen-cephalon and showed that these saponins protect neurons against the degenerative effects of 1-methyl-4-phenylpyridinium-iodide (74). In addition, pretreatment with ginseng total saponin prevents the methamphetamine-induced striatal dopaminergic depletions (75).

Acanthopanax trifoliatus (L.) Merr. (Acanthopanax aculeatus Seem, Eleutherococcus trifoliatus) is a deciduous shrub that grows up to 6 m in a geographical area ranging from the eastern Himalayas to Japan and south into Cambodia, Laos, Vietnam, and the Philippines. The stems are light brown and smooth. The leaves are spiral and trifolio-late; the folioles are broadly elliptic, grayish-green, and glossy. The folioles are 5 X 3 cm and show four pairs of secondary nerves. The apex is acuminate, the base is rounded, and the margin is crenate at the apex. The inflorescences are globose umbels, which are 3 cm in diameter and bear about eight flowers (Fig. 66).

The plant is used to treat leprosy; the roots are used to heal ulcers and to cure ringworm infection. A decoction of the leaves is drunk to treat tuberculosis and to improve general weakness. In Cambodia, Laos, and Vietnam, an infusion of the bark is used to correct nervous affections. The plant is known to elaborate lupane triter-pene saponins and kaurane diterpenes including 16-aH, 17-isovalerate-ent-kauran-19-oic acid, which strongly inhibited the enzymatic activity of cyclooxygenase in vitro (76,77).

Acanthopanax ricinifolius Seem. (Kalopanax ricinifolius [Sieb. & Zucc.] Miq, Kalopanax pictus [Thunb.] Nakai, Acer pictum [Thunb], Acanthopanax ricinifolium [Sieb. & Zucc.] Seem, Kalopanax septemlobus Koidz. var septemlobus, Panax ricinifolium Siebold & Zucc, Kalopanax ricinifolium Miq, Kalopanax pictum Nakai), or prickly ginseng, castor Aralia, prickly castor oil tree, or tzu chhiu-shu (Chinese), is a deciduous tree that grows to 25 m in Siberia, Korea, Japan, and China. The bark is gray mottled with yellowish-white; the stems are thorny and the leaves simple and palmate (Fig. 67).

Fig. 67. Acanthopanax ricinifolius Seem.

The wood is valuable as timber. In China, the bark and leaves are used for insecticide, for the treatment of skin diseases, and to heal sores and ulcers. In Korea, the bark is used for the treatment of rheumatisms, cold, and cough. In Cambodia, Laos, and Vietnam, an infusion of leaves is drunk to promote digestion. The anti-inflammatory property of the plan is confirmed in vitro and thought to be imparted by saponins, including kalopanaxsaponin A and pictoside A, which elicited significant anti-inflammatory and anti-oxidant activity in rodents (78-82). What is the dopaminergic activity of kalopanaxsaponin A and pictoside A?

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