Distribution and Importance of Perilla Plants
Perilla frutescens (L.) Britton var. crispa (Thunb.) Decaisne, belonging to the family Labiatae, is distributed widely in Japan, China, and southeast Asia. It is an annual herb about 1 m in height, and includes several forms such as f. purpurea Makino (Chirimen-aka-shiso or Aka-shiso) and f. viridis Makino (Chirimen-ao-shiso or Ao-shiso) having deep red-purple and green leaves, respectively. Perilla plants contain essential oil at about 0.5% of fresh leaf weight and give out a fragrance, principles of which are Perilla-aldehyde (55%), d-limonene (20-30%), and α-pinene (); linoleic, stearic, and palmitic acids are also contained as the major aliphatic acids. According to the extensive study on pigments of Chirimen-aka-shiso, 16 kinds of flavonoids including five anthocyanins, two flavones, and nine flavone glycosides are present in the mature dark-red leaves and seeds. Among these flavonoids, the 3-p-coumaroylglucoside-5-glucoside of cyanidin (shisonin) and the 7-caffeoylglucosides of apigenin and luteolin are the major component in the leaves. In seeds, apigenin and luteolin are present in a ratio of about 1:1. With other phenolics, a large amount of caffeic acid derivatives are present in the leaves.
Perilla plants are used for various purposes as both food stuff itself and garnish in Japanese cooking. Red-purple or green Perilla leaves, spikes, and seeds are also used as spices for buckwheat noodle, baked fish, fried food (tempura), etc.. The red-purple leaves of Aka-shiso have also been used for coloring umeboshi which is a pickled ume (Japanese apricot, Prunus mume Sieb. et Zucc), but recently there has been increased demand for the red-purple leaves of Chirimen-aka-shiso because of the presence of a large amount of the anthocyanin, shisonin.
Conventional Practices for Propagation, Production of Medicinal Components, and Demand on the Market
Perilla seedling grows moderately at about 25 °C and is a short-day plant. Seed is about 1.5 mm in diameter and the weight of 100 seeds is about 0.2 g. Seeds produced in autumn are dormant until spring and their life span is usually 2 years when stored in a refrigerator. Germination rate of the first-year seeds is about 60-80%.
Perilla plants are known as a herbal medicine, being effective as diaphoretic, anodyne, sedative, diuretic, and cough remedy, and they have powerful antiphlogistic activity due to the presence of rosmarinic acid. Essential oil of Perilla plant functions as a strong antiseptic. Fresh, and some salted leaves (sisoyoo), seeds (sisosi), and the whole mature plants are marketed throughout the seasons. Although their prices on the market depend on the season, it is usually about 200 yen per kilogram of fresh plants. Essential oil of the Perilla plant (siso-oil) is sold by the druggist.
Perilla: Conclusions and Prospects
Caffeic and rosmarinic acids are useful secondary metabolites as an antiphlogistic agent and for other remedies. The cell suspension culture of Perilla frutescens var. crispa produces caffeic and rosmarinic acids and caffeoylglucose as the major phenolic extractives. Perilla callus was induced from 6-7-day-old seedlings with Murashige and Skoog’s basal medium supplemented with 2,4-D (1 mg/1) and kinetin (0.1 mg), which was the most effective for inducing the callus. The cell suspension culture was maintained in the modified Schenk and Hildebrandt medium supplemented with 2,4-D and kinetin. The doubling time of the cells in the logarithmic growth phase was about 60 h. Total caffeic acid content of the cells in the stationary growth phase corresponds to 0.5% and 9.5% of fresh and dry weights, respectively. The lowering of 2,4-D concentration and the high kinetin concentration in the medium increased caffeic acid formation. The best medium for the formation of caffeic acid was Murashige and Skoog’s basal medium supplemented with 2,4-D (1 mg/1), kinetin (5 mg/1), sucrose (30 g/1) and agar (0.9% w/v). It is easier to isolate caffeic and rosmarinic acids from the cell suspension cultures than from the intact plants. It is also possible that the Perilla cell suspensions having a high caffeate content are constantly supplied to the market as a medicinal source throughout the seasons.
Selections from the book: “Medicinal and Aromatic Plants III”, 1991.