Myrica esculenta (PROSEA)
Introduction |
Myrica esculenta Buch.-Ham.
- Protologue: D. Don, Prod. Fl. Nep.: 56 (1825).
- Family: Myricaceae
- Chromosome number: 2n= unknown
Synonyms
- Myrica farquhariana Wallich (1826),
- Myrica sapida Wallich (1826),
- Myrica nagi auct. non Thunb.
Vernacular names
- Box myrtle (En)
- Indonesia: ki keper (Sundanese), samben, woru gesik (Javanese)
- Malaysia: telur chicak, gelincek, kesami (Peninsular)
- Thailand: metchun tua phuu (Phangnga), ruesee sek (Chai Nat), maak-mon-on (Shan-Chiang Mai).
Origin and geographic distribution
Box myrtle is native to a large part of South Asia. It is found in the Himalayas of Nepal, in southern China east to Guangdong province, in northern India, Burma, Indo-China and Thailand. In Malesia it occurs in Peninsular Malaysia, the Philippines, and Indonesia (Sumatra, Kalimantan, Java, the Lesser Sunda Islands). Box myrtle is very rarely cultivated.
Uses
In China the bark is a major source of tannin extract which is used to tan hides into leather. In India the bark is only occasionally used for this purpose. It contains a yellow colouring matter, which can be used to dye mordanted cotton yellowish to brownish shades.
The fruits are edible, tasting sourish sweet, and are used in desserts and in the preparation of a refreshing drink. In the sub-Himalayan region of India they are reported to be one of the tastiest wild fruits and are eagerly collected. The wax-like substance which covers the fruits is sometimes separated by boiling in water, and is used for making candles and soap. A decoction of the bark is used as a traditional medicine against diarrhoea, affections of bronchial tubes and lungs, dysentery and fevers.
Production and international trade
In 1987 the production of tannin extract in China was 20 000 t, for which about 60 000 t of bark of box myrtle is needed. The tannin extract is primarily used in the domestic leather industry, but a few thousand tonnes per year are exported to South-East Asian countries. As a result of excessive bark-peeling, the number of trees has decreased considerably in China in recent years, but no statistics are available. Outside China, the bark has been used only occasionally as a tanning material. The bark price in 1990 in China is US$ 120 per t.
Properties
The bark contains 18.6-33.7% of tannin on dry weight basis. The tannin is a mixture of partially galloylated polymeric prodelphinidins. An aqueous extract from the bark contains sludges which can be made soluble by treating with bisulphite. The spray-dried tannin extract is a light brownish-yellow powder, containing less than 12% water, 66-70% tannin and 2-6% precipitate, depending on quality. The tannin extract is characterized by a relatively high penetration rate and a light colour of the leather. It is used alone or blended with other tannin extracts. Hides tanned with box myrtle bark in India are reported to crack easily and the leather to be somewhat darker than leather tanned with wattle bark.
The yellow colouring matter from the bark is myricetin, C15H10O8, present in the bark as the glycoside myricitrin, C21H20O12. The edible portion of the fruit is its juicy pulp, which constitutes 75% of the whole fruit. The juice contains about 4 mg of vitamin C per 100 ml. The timber is rather closely grained and reddish-brown in colour.
Botany
- A small, evergreen dioecious tree, up to 15 m tall, trunk up to 40 cm in diameter, crooked and irregularly branched; bark greyish-brown, 5-15 mm thick; buds and twigs usually clothed with long hairs, mixed with scattered sessile glands.
- Leaves spirally arranged, coriaceous, lanceolate-obovate or oblong-obovate, (2.5-)5-18 cm × 1-4.5 cm, usually cuneate at base, acute or obtuse at apex, entire or sometimes coarsely serrate, more or less glabrous and minutely glandular beneath, exstipulate; petiole 2-10 mm long.
- Flowers in catkins, which are arranged on up to 8 cm long stalks in leaf-axils; each flower subtended by a bract; male flowers with (2-)4 stamens, anthers red; female flowers with an initially hairy ovary and two filiform-subulate stigmas.
- Fruit an ellipsoid drupe, 1-2 cm long, beset with rounded tubercles, red when ripe, 1-seeded.
Fruits mature in about 6 months after flowering. In South-East Asia box myrtle can be found flowering and fruiting throughout the year.
Myrica esculenta has often been confused with the closely allied Myrica rubra (Lour.) Sieb. & Zucc., which is cultivated in China, Korea and Japan for the fruits. It cannot be excluded that the latter species is conspecific.
Ecology
In South-East Asia, box myrtle occurs in light forests, where it is locally numerous. It prefers dry, well-drained soils, and can be found on sandy dunes and stony laterites, from the lowland up to 1700 m altitude. In India and China, box myrtle grows in a subtropical climate on hills and mountains at 900-2100 m altitude.
Handling after harvest
After the trees have been felled, the bark is peeled from the trunk, cut into short segments and air-dried. The pieces of commercial bark in China are less than 5 cm long and packed in sacks of 40-50 kg. An aqueous extract of the bark can be spray-dried to a powder with high tannin content. The fruits remain fresh for 2-3 days only. A major problem in India is that the harvesting period is too long and fruits from a single tree have to be harvested in many pickings. Trees yield 15-25 kg of fruits per year.
Prospects
Box myrtle is not extensively used in South-East Asia. Occasionally it is used as fuelwood and the fruits are eaten. As the bark has shown good tanning properties in China, box myrtle is a promising source of tanning material for the local leather industry of South-East Asian countries. The species should be cultivated to counteract the rapid decline in the number of wild trees in China in recent years.
Research should concentrate on the tanning properties, methods of propagation and cultivation, and improvement of fruit quality.
Literature
- Backer, C.A., 1951. Myricaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana, Series 1. Vol. 4(3). pp. 277-279.
- Parmar, C. & Kaushal, M.K., 1982. Wild fruits of the sub-Himalayan region. Kalyani Publishers, New Delhi-Ludhiana, India. pp. 49-53.
- Sastri, B.N. (Editor), 1962. The wealth of India. Raw materials. Vol. 6. Council of Scientific and Industrial Research, New Delhi, India. p. 472.
- Sun, D., Zhao, Z., Wong, H. & Foo, L.Y., 1988. Tannins and other phenolics from Myrica esculenta bark. Phytochemistry 27(2): 579-583.
Authors
Chu Chengde & Sun Dawang