Swertia japonica Makino and Swertia pseudochinensis Hara, biennial herbs of the family Gentianaceae, are found wild on sunny slopes of hills and mountains. Swertia japonica, 5-40 cm high, growing wild in Japan, Korea, and China, bears white five-petaled flowers with purple streaks in the autumn. Swertia pseudochinensis, growing wild in Japan, Korea, and the temperate regions of Southeast Asia, is much like Swertia japonica in external appearance, although it is a little larger and bears bright bluish purple flowers with purple streaks. All the parts of these herbs collected at flowering have been used as Japanese folk remedies as stomach bitters. Swertia japonica is especially important and officially listed in the Japanese pharmacopoeia, because it has the bitterest taste in the genus Swertia; it is now being tried as a hair tonic. On the other hand, Swertia pseudochinensis is inferior in the quality of its bitterness, which is explained by the chemical fact that this herb contains swertiamarin, which is less bitter than amarogentin and amaroswerin, which Swertia japonica contains, together with sweroside as major bitter constituents.Other species of this genus found wild in Japan are not used as medicinal plants. Chiretta, Swertia chirata Hamilton an annual herb of a height of about 1 m indigenous to mountainous districts of northern India, has been used as a tonic rather than a stomach bitter in India. The only countries which use the genus Swertia for medicinal purposes are Japan, China (Tibet), and India. Thus there are almost no Swertia species in use as bitters except Swertia japonica and Swertia pseudochinensis. In spite of the great demand for these herbs, their supplies still depend on wild sources which are becoming critical on account of the overharvesting of the plants and the progressive clearance of their habitats. It would therefore certainly be helpful to utilize in vitro culture techniques to ensure the supply of the crude drugs from these herbs and the production of secondary metabolites. Clonal propagation of plants for agricultural and horticultural uses has been carried out for a long time, and it is already being put to practical use in plants of various kinds; but also studied on the micropropagation of medicinal plants and the production of secondary metabolites are now increasing from year to year in spite of a belated start.
Swerti: Conclusion and Prospects
On White’s medium containing 10% CM and 1 mg/1 2,4-D, callus tissues were successfully derived from seedling root. The calli maintained on the medium for over 2 years were used to determine the cultural requirements of callus. By the addition of 2,4-D 1 mg/1, IAA 10 mg/1, or NAA 10 mg/1 to the medium containing kin 0.01 mg/1, successful growth of callus was obtained without the supplement of CM. Shoots were induced from callus on the medium containing BA 1 mg/1 and CH 2 g/1 under continuous light. They continued to grow on a hormone-free MS medium without rooting.
The parent plant of Swertia japonica contains bitter glucosides having a strong, bitter taste, whereas it was found that callus tissues had no bitter taste and no bitter glucosides. Therefore, the speedy establishment of an in vitro method for cultured tissues and /or regenerated plants with medicinal qualities is greatly needed for Swertia japonica. To accomplish this purpose, results successfully obtained from tissue culture studies of Swertia pseudochinensis may be a great help.
Root and leaf developments of seedlings were observed at NAA 0.01 mg/1 + BA 0-0.1 mg/1 and NAA 0-0.1 mg/1 + BA 1-10 mg/1, respectively. Callus was induced at NAA 0.1-1 mg/1 + BA 0-1 mg/1 from hypocotyls and roots and subcultured on the medium containing NAA 1 mg/1. After 3-4 weeks in culture on the same medium, numerous embryoids were formed in the embryogenic calli, which were developed to plants when cultured for 2 months. The plants obtained were transferred to pots containing a mixture of sand and peat moss and continued to grow.
Excised root cultures were obtained from root tips of the seedlings. Successive cultures were maintained by subculturing root tips at 6-8-week intervals for 2 years. Their best growth was obtained when cultured in half-strength B5 liquid medium containing NAA 1 jug/1 and sucrose 3% in dim light.
Swertiamarin was present in 5- and 8-month-old regenerated plants, but not in roots of 5-month-old ones. It is particularly interesting from the viewpoint of bitter glucoside biosynthesis that swertiamarin exists in regenerated plants but in neither roots or leaves cultured separately. The regenerated plants obtained may be useful not only for medicinal source plants, but also for a simple experimental system for studies on the bitter glucoside biosynthesis because they contain predominantly swertiamarin, the same as the original plants.
Selections from the book: “Medicinal and Aromatic Plants III”, 1991.