Characteristics and Morphology of Dendrobium

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Orchidaceae, the second largest plant family, is the most diverse and highly evolved amongst angiosperms which constitute about 40% of the monocotyledonous taxa. The recent taxonomical studies imply that distinctly named varietal number of orchids fall very close to a total of 19,000 comprising 800 genera and 25,000 species (Lahaye et al., 2008). Orchids mostly comprise of epiphytes whose greatest diversity occurs in tropical and sub-tropical regions. India has a rich heritage of wild orchids in the world. It is estimated that nearly 1,600 species are found in India which constitute approximately 10% of world orchid flora. High humidity and low temperature accompanied by good rainfall makes Assam, Manipur, Western Ghat regions of the country prime hot spots of orchids. Orchids are undoubtedly the ornamentally elite group owing to their perplexing complex floral features with exquisite beauty. The flowers comprise two whorls of petaloid organs termed tepals which encircle the reproductive organs of the plant. Morphological features like the size and shape of the column, presence of appendages, conformation, position and number of the anthers, as well as characteristics of the pollinia and other structures of flowers help us to identify species-specific variations.

Bulbophyllum is the largest genera with 2,000 species, closely followed by Epidendrum with 1,500 species and Dendrobium with 1,400 species. Dendrobium is the third largest genus of orchid family characterized by a broad geographical distribution with tremendous diversity in growth habits. It also exhibits a unique ability to produce a large number of inter-specific floral hybrids possessing high commercial demand. Dendrobium habitat extends from India in the west, to Ja...

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...mpounds in Dendrobium plants include a group of sesquiterpene alkaloids and phenols (Okomoto et al., 1966; Elander et al., 1973; Tang and Eisenbrand, 1992). Moscatilin (Fig. 1) is a bibenzyl phenol derived from Dendrobium species. It is also known as dendrophenol, Phenol, 4-(2-(4-hydroxy-3-methoxyphenyl) ethyl)-2,6-dimethoxy-. In the year 1987, moscatilin was first extracted from Dendrobium moscatum (Mazumdar and Sen, 1987) and it was later isolated from several other species such as Dendrobium loddigesii (Chen et al., 1994), Dendrobium amoenum (Mazumdar et al., 1999), Dendrobium nobile (Miyazawa et al., 1999), Dendrobium densiflorum (Fan et al., 2001), Cymbidium aloifolium (Juneja et al., 1987) and Agrostophyllum khasiyanum (Mazumdar et al., 1996). Studies have proved the anti-cancer activity of moscatilin in stomach and lung cancer cell lines (Ho et al., 2003).

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