Distribution of Scutellaria
The genus Scutellaria belongs to the family Labiatae and subfam. Scutellarideae. Scutellaria is widely distributed all over the world except for South Africa, and there are about 300 species. The calyx of this genus is remarkably specialized to become two-lip-shaped, and characterized by the upper lip having a flat or dish-shaped upper surface on which a small swelling forms; the dish-shaped part peels offat fruit maturation to allow a seed to fall.
The 15 species, such as S. maekawa Hara, S. brachyspica Nakai et Hara, S. laeteviolace Koizumi, S. iyoensis Nakai and others are distributed only in Japan. Further S. indica L., S. indica var. parvi flora Makino, S. sterigillosa Hensl, S. dependens Maxim, and others are distributed over wide areas in Japan, the Korean Peninsula, the northeastern section of China and the Indonesian Peninsula. Furthermore, S. baicalensis Georgi is native to the region from the northern section of China to Siberia. It was introduced into Japan from the Korean Peninsula in the middle period of the Edo era and has been cultured in various parts of Japan for the medicinal uses of the root. In Japanese Pharmacopoeia the root of S. baicalensis Georgi, excepting the exodermis, is used as medicinal Wogon (Scutellariae Radix).
In China, many plants belonging to the Scutellaria genus are distributed and the root of Scutellaria baicalensis Georgi is mainly used as medicinal Wogon but the following seven species are also used as a source for medicinal Wogon, S. viscidula Bye, S. amoena Wright, S. rehderiana Diels, S. likiangesis Diels, S. ikonnikovii Juz., S. hypericifola Levl., and S. rivularis Wall (Ban Zhi Lian). Further, in the Alpine districts of Europe, Scutellaria alpina L. and Scutellaria costericana H. Wendel are distributed and cultured as garden species for their attractive flowers.
Studies on the constituents of Scutellaria species have been made, i.e., S. amoena C.H. Wright), S. viscidula Bunge, S. rivularis Wall S. discolor Colebr, S. indica L., S. scandens Buch, Ham ex D. Don, and others.
Importance of Scutellaria baicalensis
Wogon is one of the crude drugs frequently used as an important medicine in Chinese clinical practice. The origin of this crude drug is the plant Scutellaria baicalensis Georgi, and its root, excepting the exodermis, is prescribed in the Japanese Pharmacopoeia JPXI and compounded in many Chinese medicines including Sannosan and others, for treatment of diarrhea, abdominalgia, anorexia, hot flash, stiffness of the shoulders, agrypnia, or the like. S. baicalensis is a perennial plant native to the region from the north section of China to Siberia, as mentioned above, and grows to a height of 30-60 cm, spreading in a semi-spherical shape, with a lanceolar leaf having many hairs. From June to July, the leading end of each branch produces purple ear-shaped flowers and the root is long and conical in shape, the interior showing a golden color.
The study of components of Wogon prepared from plants originated from Scutellaria baicalensis has concentrated on flavonoids, and about 40 kinds of flavonoids ranging from flavonoids relatively high in content such as baicalin, baicalein, wogonin or the like to minor flavonoids have been isolated and reported up to now. Other components are β-sitosterol, camphesterol, and stigmasterol, two kinds of sugars (glucose and sucrose), three kinds of amino acids structurally unknown, and tannin. Many pharmacological functions, e.g. to eliminate bile acid or to act as a diuretic laxative, anti-inflammatory, or anti-allergic factor, lipid metabolism and arachidonate metabolism, and similar have been confirmed. These pharmacological effects are considered to be mainly brought about by the flavonoids contained in Wogon. The anti-allergic effect of Wogon is said to be developed by the chromone, thus being the base nucleus of baicalein, and is the source for developing anti-allergic drugs.
A Fundamental Study of the Cultivation of Scutellaria baicalensis Georgi
Detailed study of seasonal variations of growth and flavonoid content has been reported by Tomimori et al.. The dry weight and flavonoids of the root gradually increased over 3 years, although it decreased during the resting periods. During budding, some flavone glucuronides were hydrolyzed to form aglycone and glucosidation was accelerated in the flowering and fruit-bearing periods. The baicalin content was highest in the latter half of fruit-bearing, and was almost the same as in the root of the 3-year-old plant; ca. 40% of the roots were delayed after fruit-bearing. It is therefore considered that from the viewpoint of both yield and quality, the root of S. baicalensis should be harvested in the second year in the latter half of the fruit-bearing period (in late autumn).
In the basic research on the formation of flavonoids in liquid culture of Scutellaria baicalensis (), two-stage liquid cultures and the culture of differentiated roots are still being studied for the purpose of mass proliferation of flavonoids (baicalein, baicalin) having anti-allergic action. The experiments on cultured tissue of S. baicalensis were performed from the following two viewpoints to obtain a definite result.
1. Various culture conditions are investigated using cultured cells of Scutellaria baicalensis and a useful substance is specifically formed, that is, flavonoids are isolated to be used as medicines.
2. The flavonoid pattern and content of S. baicalensis callus cultures are allowed to approach a crude drug Wogon, and Scutellaria baicalensis is made utilizable in a herb medicine recipe as a substitute medicine for the so-called Wogon.
Selections from the book: “Medicinal and Aromatic Plants III”, 1991.