Comparison of contents of polysaccharides and alkaloids in Dendrobium from different harvest time

OBJECTIVE To determine the best harvest time for higher contents of polysaccharides and total alkaloids,the main active components of D. nobile Lindl and D. candidum Wall. ex Lindl in the different growth time( 1,2,3 years) from Chishui in Guizhou province. METHOD Three batches of Dendrobium were collected from the same area in different growth time. The content of Dendrobium polysaccharides was detected with phenol sulfuric acid colorimetry at 490 nm. The content of total alkaloids in Dendrobium was detected with acid stain colorimetry at 620 nm. The content of dendrobine was detected with gas chromatography. RESULTS The linear relationship was good between concentration and absorbance of Dendrobium polysaccharides in the range of 4. 95-39. 95 μg·mL-1( r =0.9969). The contents of polysaccharides( 1,2,3 years) in Dendrobium nobile were 7.74%,2.75%,2.20%,respectively.The contents of polysaccharides( 1,2,3 years) in Dendrobium candidum were 40. 40%,30. 96%,48. 87%,respectively. The contentsof total alkaloids( 1,2,3 years) in Dendrobium nobile were 0. 5489%,0. 4166%,0. 3255%,respectively,the contents of total alkaloids( 1,2,3 years) in Dendrobium candidum were 0. 0114%,0. 0111%,0.0121%. The contents of dendrobine in Dendrobium nobile were 0. 2212%,0. 2229%,0. 1129%,while in Dendrobium candidum,dendrobine was hardly detectable. CONCLUSION The contents of polysaccharides and total alkaloids in Dendrobium nobile and in Dendrobium candidum are the highest in one year,and 3years,respectively. Which is the best harvest time.