Inhibitory Effects of the Standardized Extract of Phyllanthus amarus on Cellular and Humoral Immune Responses in Balb/C Mice.

Phyllanthus amarus has been shown to have strong inhibitory effects on phagocytic activity of human neutrophils and on cellular immune responses in Wistar-Kyoto rats. In this study, we investigated the effects of daily treatment of standardized extract of P. amarus at 50, 100 and 200 mg/kg for 14 days in Balb/C mice by measuring the myeloperoxidase activity (MPO), nitric oxide (NO) release, macrophage phagocytosis, swelling of footpad in delayed type hypersensitivity (DTH), and serum immunoglobulins, ceruloplasmin and lysozyme levels. Qualitative and quantitative analyses of the extract using validated reversed-phase HPLC methods identified phyllanthin, hypophyllanthin, corilagin and geraniin as the biomarkers. Significant dose-dependent inhibitions of MPO activity and NO release were observed in treated mice. The extract also inhibited E. coli phagocytic capacity of peritoneal macrophages of treated mice and inhibited the sheep red blood cells (sRBC)-induced swelling rate of mice paw in the DTH. There was also a significant decrease in non-specific humoral immunity including ceruloplasmin and lysozyme levels in the extract-fed groups as well as the release of serum level immunoglobulins. The strong inhibitory effects of the extract on the cellular and humoral immune responses suggest the potential of the plant to be developed as an effective immunosuppressive agent.