Introduction

Schisandrin B (Sch B, Fig. 1a) is the most abundant dibenzocyclooctadiene derivative (lignan) isolated from Fructus Schisandrae (FS), the fruit of Schisandra chinensis (Turcz.) Baillon, or Wu-Wei-Zi, meaning the fruit of five tastes in Chinese. FS is a commonly used herb in traditional Chinese medicine (TCM). The plant grows as a woody aromatic vine, with fruits occurring as bunches of berries on a short, drooping spike. The plant is native to most Eastern parts of Russia (Primorsk and Chabarowsk regions), northeastern China (Jilin, Liaoning, Heliongjiang, and Hebei provinces), North Korea, and Japan (1). In terms of pharmacological properties, TCM characterizes Wu-Wei-Zi as "warm" in nature and mainly ''sour'' in taste, with the regulatory/therapeutic action targeted at the ''lung-kidney'' as well as ''liver-heart'' functions. Traditionally, the herb is used as astringent and sedative, as well as in tonic formulae for invigorating the qi (vital energy) of the five viscera, namely, liver, heart, spleen, lung, and kidney, in the body (2).

(a) Schisandrin B
(e) Gomisin A
(g) Schisandrol A
(b) Schisandrin A
(d) Dimethyldiphenyl bicarboxylate (DDB)

(f) Schisanhenol

Figure 1 Chemical structures of schisandrin B and other dibenzocycloocta-diene lignans.

Figure 1 Chemical structures of schisandrin B and other dibenzocycloocta-diene lignans.

Starting from the 1950s, pharmacological studies on FS were focused mainly on examining its effect on cardiopulmonary function and the central nervous system. Since then, FS has been regarded as an adaptogen that can increase the resistance of the body against nonspecific stimuli (3). At the beginning of the 1970s, a number of clinical investigations unequivocally demonstrated the effectiveness of FS for the treatment of chronic viral and chemical hepatitis, particularly in lowering the elevated serum glutamic-pyruvate transaminase (GPT) activity (4). In an experimental model of hepatitis used as activity monitor, the activity-directed fractionation of FS extract yielded a series of lignans including Sch B (5). During the past two decades, the hepatoprotective mechanisms of Sch B and other lignans derived from Fructus Schisandrae have been extensively investigated, particularly those involving hepatic microsomal cytochrome P-450-dependent drug-metabolizing enzymes (6-8). While the tissue-protective action of Sch B was found not only limited to the liver, protection against free-radical-mediated injury was demonstrated in both heart and brain tissues in experimental animals (9,10). The apparently broad-spectrum and tissue-nonspecific protection afforded by Sch B and other lignans has attracted much interest in the area of preventive medicine. Thorough understanding of biochemical mech-anism(s) of Sch B involved in tissue protection against noxious stimuli is instrumental in expediting its use in modern medicine. In the following sections, the pharmacological profile of Sch B and other structurally related lignans will be first described, followed by discussion of the biochemical mechanism(s) involved in various tissue protective actions.

Traditional Chinese Medicine

Traditional Chinese Medicine

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