Background: Standardized extract of Phyllanthus amarus has been shown to possess
inhibitory effects on cellular and humoral immune responses in Wistar-Kyoto rats and Balb/c mice.
Objective: In the present study, the standardized extract of P. amarus was investigated for its
suppressive effects on type II collagen-induced rheumatoid arthritis (TCIA) in Sprague Dawley rats.
Method: The major components of the extracts, lignans and phenolic compounds were analysed by
using a validated reversed phase HPLC and LC-MS/MS. A rheumatoid arthritis rat model was induced
by administering a bovine type II collagen emulsion subcutaneously at the base of tail, on day 0 and 7
of the experiment. Effects of the extract on severity assessment, changes in the hind paw volume, bone
mineral density, body weight and body temperature were measured. Concentrations of cytokines
(TNF-α, IL-1β, IL-1α, IL-6) released, matrix metalloproteinases (MMP-1, MMP-3 MMP-9) and their
inhibitor (TIMP-1), haematological and biochemical changes were also measured. ELISA was used to
measure the cytokines and proteinases in the rat serum and synovial fluid according to manufacturer's
Results: The extract dose-dependently modulated the progression in physical parameters (i.e. decrease in
body weight, increase in body temperature, reduced hind paw volume, reduced the severity of arthritis),
bone mineral density, haematological and biochemical perturbations, serum cytokines production and
levels of matrix metalloproteinases and their inhibitor in the synovial fluid. Histopathological examination
of the knee joint also revealed that the extract effectively reduced synovitis, pannus formation, bone
resorption and cartilage destruction.
Conclusion: The results suggest that the oral administration of a standardized extract of P. amarus was
able to suppress the humoral and cellular immune responses to type II collagen, resulting in the
reduction of the development of TCIA in the rats.