The genus Zingiber, the type genus of the family Zingiberaceae, forms an important group of the order Zingiberales. The word ginger refers to the edible ginger of commerce, Zingiber officinale. Ginger is also the common term for the members of the ginger family, Zingiberaceae, which includes the many other species of Zingiber besides Z. officinale, worth growing as ornamentals, while some are valuable medicines. Many species are grown in the garden as ornamentals. They bear showy, long-lasting inflorescences and often brightly colored bracts and floral parts; they are widely used as cut flowers in floral arrangements. The gradual changing of the inflorescence bracts from green to yellow to various shades of red and finally to deep red adds to the beauty of the inflorescence. Many wild species have great ornamental potential. Some of them are good foliage plants due to their arching form and shining leaves. Leaves exhibit shades of light green to dark green, variegated with yellow and white, or with deep purple undersurfaces. Many of the inflorescence bracts, when squeezed, release a thick juice with the form of mucilage, or a shampoo-like substance. Hence, those gingers having this mucilage in their bracts are called shampoo gingers. The following is a brief description of the Zingiber species having economic importance as local medicine, as spice, or as ornamental plants.
The plants are perennial, medium-sized herbs with stout rhizomes. Most of the species produce the inflorescence on a separate shoot directly from the rhizome, at the tips of a short or long peduncle. In a few species, the inflorescence develops at the tips of the leafy shoots (Z. capitatum). The inflorescence possesses a number of closely overlapping bracts, each bearing a single flower. The flowers are peculiar in that the lateral staminodes are fused with the labellum, whereas in other genera they are free, highly reduced, or absent. The anther is unique in having a curved beak or horn-like appendage. This genus resembles other genera such as Alpinia, Amomum, Hedychium, etc., and so on in the vegetative stage, but it can be distinguished from others because it has a pulvinus at the base of the petiole. The rhizome and pseudostem of Zingiber spp. are fleshier when compared with Alpinia, Amomum, and so on. The duration of the flowers in the genus is very short and differs from one species to another, but it is constant for each species. In Z. zerumbet, the flowers open from morning until evening in an inflorescence.
The flowers are usually cross-pollinated. The pollination in the species of Zingiber is rather simple because of the specially modified anther structure and nature of staminodes. An insect visiting a flower first lands on the labellum and moves to the throat of the corolla tube. When the insect's front portion pushes the base of the anther, the anther bends forward and dusts the pollen grains on the backside of the insect. As it bends
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forward, the stigma protrudes and arches through the long anther crest and presses against the proboscis of the insect. Thus, pollen grains from other flowers deposited on the back of the insect stick to the stigma, and pollination is effected.
Z. mioga (myoga ginger or Japanese ginger) is a perennial woodland species, endemic to Japan, where it is most popular. It is grown for its edible flowers and young shoots, both of which are used extensively as vegetables. The flowers are mostly sterile, and the propagation of this species is through rhizome division, as in the case of true ginger. The species is unique in having a pentaploid chromosome number of 2n = 55. In Japan, it is widely grown as a seasonal crop, and the flower bud-producing season is summer. Forced production in glass houses and heated polyhouses occurs during the winter months, and the product attracts a premium price (Sterling et al., 2003). From Japan, myoga cultivation has spread to China, Vietnam, Taiwan, Thailand, Australia (Queensland), and New Zealand.
The myoga plant needs well-drained and fertile soil to grow well. Under poor drainage, plant growth is retarded, and rhizome rotting can occur. Myoga shoots emerge in the spring and produce dense foliage on robust stalks. The sterile flowers are produced at ground level from the underground stems during summer and autumn. The aerial shoot dies out during winter, and the underground stem sprouts in spring and growth continues. The crop is propagated by planting 25 cm-long rhizome pieces, planted about 10 cm deep, 40 cm apart, in rows. Harvesting the flower buds begins in the second year. An annual fertilizer application of 200 to 300 kg/ha of nitrogen—phosphorous-potassium (NPK) fertilizer is suggested (Paghat, 2003).
Myoga flower buds are picked before they emerge above surface from the underground shoots. To facilitate harvesting, a 10 to 15 cm layer of sawdust is used to mulch the plant bases. The buds are located in the sawdust and are harvested individually at the appropriate stage two to three times each week. Export-grade buds need to be above 6 g and be plum or pink in color. The harvested flower buds can be kept in cold storage, and the production is around 8 to 13 t/ha in a second-year crop (see Figure 17.1). Sterling et al. (2003) showed that flower bud production is influenced by photoperiod.
Myoga cultivation has recently become popular in Australia and New Zealand. In Australia, a superior type of myoga plant has been identified and multiplied through tissue culture on a large scale for distribution to farmers. The myoga industry in Australia and New Zealand depends on this superior line, and cultural conditions have been standardized for growing this type of ginger (Clark and Warner, 2000).
A dwarf variegated variety, known as dancing crane, is an ornamental plant, growing to about 45 cm in height and producing yellow flowers. This variant has leaves with white stripes on a green background (see Figure 17.2).
Myoga ginger is used in Japan as a spice and as a substitute for true ginger. Two compounds—galanal A and galanal B—were isolated from myoga rhizomes. These are known to contribute to the characteristic flavor of the myoga rhizomes. The pungent principle in myoga was identified as (E)-8beta(17)-epoxylated-12-ene-15,16-diel, commonly known as myogadial. When isolated, this compound, and also Galanal A and B and reduced, myogadinol are tasteless. The pungency of myogadial depends on the presence of the alpha-beta-unsaturated -1,4-dialdehyde group (Abe et al., 2002). In Chinese Pharmacopoeia, myoga ginger is used to treat fever and also as a vermifuge.
Z. montanum (Koenig) Link ex Dietr. ( = Z. cassumunar RoxbJ
Z. montanum is a native of India and is present throughout the Malaya Peninsula, Sri Lanka, and Java. It is also cultivated in tropical Asia. Its rhizome is an ingredient in many traditional medicines. It is usually used together with the rhizomes of Z. amaricanum, Z. aromaticum,
Z. officinale, and Kaempferia galanga. In the Philippines, the decoction prepared from these rhizomes is used to relieve cough and asthma (Quisumbing, 1978). The rhizome is also used as an antidiarrheal medicine in its powdered version or it is made into a paste with rice water (Saxena et al., 1981). As a paste, it can also be given twice daily for three days as an antidote to snakebite. Olivers and Bruce (1991) have proven that the oil of Z. montanum has antibacterial and antifungal properties. The rhizome is also considered a good tonic and appetizer. It is given with black pepper for cholera and also as vermifuge (Barghava, 1981).
Z. montanum is cultivated in the United States as a garden ginger and is often called "chocolate pinecone ginger." The stems are tall and thin, and the bracts are brown, thus the common name.
Z. casusmunar is propagated vegetatively through the division of suckers. The rhizomes on storage get easily affected by fungi, causing rotting. Rhizome pieces with one or two emerging shoots are used for planting immediately after separation from the mother stock. Poonsapaya and Kraisintu (2003) came out with a tissue culture multiplication protocol. Shoot tips cultured in Linsmaier and Skoog (LS) medium, supplemented with 4mgl_1 benzyl amino purine (BAP), produce an average of 13 shoots within 8 weeks. The incorporation of antibiotics is essential to suppress microbial contamination. The rooting of shoots was achieved in a medium with a low concentration of a-naphthane acetic acid (NAA) or with the addition of activated charcoal.
Many studies have been made on the medicinal properties, especially of the anti-inflammatory effect, of Z. casumunnar. Ozaki et al. (1991) isolated three compounds identified as (E)-1-(3, 4-dimethoxyphenyl) but-1-ene, (E)-1-(3, 4-dimethoxyphenyl) butadiene, and zerumbone. The methanol extract was found to possess the anti-inflammatory and analgesic activities, which come from the first compound, (E)-1-(3,4-dimethoxyphenyl)but-1-ene.
Masuda et al. (1995) isolated cassumunarins A, B, and C, three anti-inflammatory antioxidants, and determined their structures. Cassumunarins are complex curcuminoids. Their antioxidant efficiency was determined by the inhibition of linoleic acid's antioxidation in a buffer—ethanol system. The anti-inflammatory effect was measured by the inhibition of an edema formation on a mouse ear, induced by 12-o-tetradecanoyl-phorbol-13-acetate. The cassumunarins showed greater activity than curcumin in both assays.
Masuda and Jitoe (1995) isolated four phenyl butanoid monomers from the fresh rhizomes of Z. cassumunar from Indonesia:
In addition, Masuda and Jitoe also isolated three phenylbutenoid monomers that are already known.
Nugroho et al. (1996) screened the rhizomes of 18 species for insecticidal activity, and the rhizomes of Kaempferia rotunda and Z. cassumunar exhibited a marked insecticidal activity in chronic feeding bioassays at concentrations of 2,500 and 1,250 ppm, respectively. Bioassay-guided isolation led to two phenylbutanoids from the rhizomes of Z. cassumunar (an LC50 value of 121 and 127 ppm). Both compounds were active in the residue-contact bioassay (LC50 values of 0.5 and 0.36 ^g/cm2). The presence of oxygenated substitutes in the side chain nullified the insecticidal activity.
Panthong et al. (1997) assayed the anti-inflammatory activity of compound D ((E)-4-(3',4'-dimethoxy-phenyl)but-3-en-2-ol) isolated from the hexane extract of Z. cassumunar rhizome using various inflammatory models in comparison with Aspirin, indomethacin (indimetacin), and prednisolone. The results showed that the anti-inflammatory effect of compound D mediated prominently on the acute phase of inflammation. It exerted a marked inhibition of carrageenin-induced rat paw edema, exudate formation, leukocyte accumulation, and prostaglandin biosynthesis in carrageenin-induced rat pleurisy. Compound D possessed only a slight inhibition of both the primary and secondary lesions of adjuvant-induced arthritis and had no effect on cotton-pellet—induced granuloma in rats. Compound D elicited analgesic activity when tested on the acetic acid-induced writhing response in mice but had weak inhibitory activity on the tail flick responding to radiant heat. Compound D possessed marked anti-pyretic effect when tested on yeast-induced hyperthermia in rats.
Nagano et al. (1997) studied the effect of cassumunarins A and B, isolated from Z. cassumunar, in dissociated rat thymocytes suffering from oxidative stress induced by 3mM H2O 2 (hydrogen peroxide) by using a flow cytometer and ethidium bromide. The effects were then compared with those of curcumin. The pretreatment of rat thymocytes with cassumunarins (100 nM to 3^M) dose dependently prevented H2O2-induced decrease in cell viability. Cassumunarins were also more effective when administered before the start of the oxidative stress. The respective potencies of cassumunarins A and B in protecting cells suffering from H2O2-induced oxidative stress were greater than that of curcumin.
Bordoloi et al. (1999) investigated the essential oil composition of Z. cassumunar from the northeast of India using gas chromatography-mass spectrometry (GC-MS), analyzing oil hydrodistilled from rhizomes and leaves. The rhizome essential oil contained ter-penen-4-ol (50.5 percent), E-1-(3,4-dimethoxyphenyl)buta-1,3-diene (19.9 percent), E-1-(3,4-dimethoxyphenyl)but-1-ene (6.0 percent), and P-sesquiphellandrene (5.9 percent) as major constituents out of the 21 compounds identified. In the leaf essential oil, 39 compounds were identified. The main components were 1(10),4-furanodien-6-one (27.3 percent), curzerenone (25.7 percent), and P-sesquiphellandrene (5.7 percent).
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