Study On Safety Evaluation Of Dendrobium Huoshanense And Seasonal Variation Of Biochemical Characteristics Of Its Polysaccharides

Dendrobium huoshanense is an edible traditional Chinese herb with a long history. In the present study, the safety evaluation of D. huoshanense stems (DHS) was performed by acute oral toxicity test, genotoxicity test,90-day feeding test, teratogenicity test and hygiene test, and the changes in biochemical characteristics of polysaccharides of D. huoshanense harvested in different seasons were analyzed. The main results obtained were as follows:(1) Acute oral toxicity test showed that the maximum tolerable dose of DHS in both male and female mice were more than 15.0 g/kg.bw.(2) The genotoxicity test showed that DHS had no significant mutagenicity to strains of Salmonella typhimurium TA97, TA98, TA100 and TA102 in Ames test, no significant effect on micronucleus rate changes and Polychromatic Erythrocyte (PCE)/Normochromatic Erythrocyte (NCE) ratio of mouse bone marrow cells, and a mouse sperm abnormality rate (1.82%-1.90%) that is similar to that of the negative control (1.76%).(3) In the 90-day feeding test, no significant differences in body weight, body weight gain, food intake, food utilization rate, the absolute weight of major organs, organ-to-body weight ratio, hematological parameters and serum biochemical indexes in rat between the control and DHS groups. Moreover, gross examination and histopathological examination revealed no abnormal changes associated with the tested substance.(4) Teratogenicity test showed that no adverse effect was observed with DHS on the body weight gain of pregnant rats, the early development of embryos as well as the development, skeletons, viscera and appearances of fetuses.(5) Hygiene test showed that the contents of organic chlorine pesticide residues (BHC, DDT) and heavy metals (Pb, Cd, Hg, As, Sn, Ni) as well as the microbiological indexes (aerobic plate count, coliform, mold, yeast, Salmonella, Staphylococcus aureus) were all accorded with the national standards.(6) The biochemical characteristics of polysaccharides varied with seasons. The polysaccharide content of D. huoshanense harvested in winter was higher than that in summer. The maximum content of polysaccharides occurred in January (40.107 g/100g dry weight) and the minimum in August (20.093 g/100g dry weight). Similar phenomenon existed in the change in viscosity of polysaccharides, which reached the maximum in December (0.430 dl/g) and the minimum in August (0.228 dl/g). The polysaccharides of D. huoshanense harvested in different seasons were all mainly composed of glucose and mannose with different molar ratios, which were between 1.93:1.00 and 3.18:1.00. The polysaccharides of D. huoshanense had the potential to regulate intestinal mucosal immune activity. The polysaccharides of D. huoshanense harvested from November to April showed higher intestinal mucosal immunomodulatory activity than those from May to October.In conclusion, DHS is safe and has no toxicity. Its best harvest period is during November and April according to the biochemical characteristics of polysaccharides. These results will provide a solid foundation to apply for the approval of D. huoshanense as novel food material.