Abstract: Objective To investigate the acute,sub-chronic,genetic,and immune toxicity of Sauropus androgynus and to evaluate its safety.Methods The leaves and stems of Sauropus androgynus were made into fresh homogenate(FH) or dehydrated into pow der(P) for acute and sub-chronic oral toxicity test.The filtered fresh homogenate(FFH),filtered fresh homogenate heated(FFHH),and filtered fresh homogehate concentrated(FFHC) were made for cytotoxicity with neutral red uptake test (NRU),genetic toxicity with mammalian chromosome aberration in vitro,and immune toxicity with 3-(4,5dimethylthiazol-2-yl)-2,5 diaphyl-2,5 diphenyl-2-tetrazolium bromide(MTT) assay and flow cytometer.Results The medium lethal dose (LD₅₀) of FH was greater than 21.5 g/kg·bw and that of P was above 20.0 g/kg·bw.In sub-chronictoxicity test,all the indexes and values were in normal ranges with the treatment of FH,even at the concentration of up to 10.0 g/kg·bw.There were significant decreases in testicle size and weight of male rats treated with P in high concentration and spermatogenic epithelium hypogenesis could be observed with histopathological examination and there was no spermatogenic cell arrayed in sequence.Under the treatment of P at the concentration of 8.00 g/kg·bw,the feed intake,body weight and serum plasma urea nitrogen,creatine,triglyceride of male rats decreased compared to those of the control group.The no observed adverse effect level(NOAEL) value of Sauropus androgynus powder was 2 000 mg/kg·bw.When Chinese hamster(CHL) cells were treated with FFH and FFHH,the cell proliferation was inhibited at low concentration,but promoted at high concentration with NRU test.The treatment of FFHC enhanced chromatid and chromosomeal aberrations in both CHL and V79 cells at 6×10² mg/ml.Compared to that of the the control group,the proliferation ability of T and B lymphocytes and the levels of tumor necrosis factor(TNF) and interferon(IFN)-γ were all inhibited significantly in the rats treated with Sauropus androgynus.The interleukin-2 (IL-2) increased at 10 and 20mg/ml and decreased at 40-320 mg/ml.The percentage of phagocytic cells increased significantly at 20-160 mg/ml and the phagocytic index increased at 10320 mg/ml.Conclusion Sauropus androgynus has no obvious acute oral toxicity,cytotoxicity and genetic toxicity and the fresh homogenate of Sauropus androsynus has no sub-chronic oral toxicity in rats.Hypogenesis and hypoplasia of testis could be observed in rats treated with high concentration of dehydrated powder of Sauropus androgynas.At low concentration of Sauropus androgynus,lymphocytes proliferation could be promoted,but could be inhibited at high concentration,which might be a hormesis phenomenon.