Optimization of light quality for production of alkaloid and polysaccharide in Dendrobium candidum Wall. ex Lindl.

The main bioactive substances of traditional medicine Dendrobium candidum are alkaloids and polysaccharides. A strategy is described for optimizing light quality to maximize the production of alkaloids and polysaccharides in D. candidum, so as to provide the basis for industrial production. Concentration of alkaloids and polysaccharides were studied by acid dye colorimetry and vitriol-phenol colorimetry, respectively, after culturing the D. candidum fewer than three light qualities: red light, blue light and white light. Production of alkaloids and polysaccharides were increasing with the growth extension under all light treatments. Explants cultured under red light contained significantly more alkaloids and polysaccharides than explants cultured under blue light, followed by white light, exhibiting that the most effective light was red light. But, upon the onset of continuous red light and blue light irradiation, growth of D. candidum decreased in a continuous manner. These observations suggested that among different light qualities, a mixture of red and nature light would be necessary for normal plant and had the potential to replace others for the large-scale production.   Key words: Dendrobium candidum, alkaloids, polysaccharides, light quality.