Abstract
The root bark of Capparis erythrocarpos (CERB) is employed to treat rheumatoid arthritis (RA) in Africa, particularly in Ghana. However, there was no isolation and characterization of the bioactive constituents responsible for the pharmacological actions of this plant. The aim of this study is to isolate, characterize and evaluate the anti-arthritic activity of the constituents of CERB. CERB was soxhleted and partitioned into various fractions. The constituents were isolated using column chromatography and characterized by 1D and 2D NMR spectroscopy. The precise carboxylic acid residues of the esters were determined using saponification, derivatization and GC-MS analysis. Anti-arthritic activity was evaluated in the CFA-induced arthritic model. Two triterpenoid esters namely, sitosterol 3-hexadecanoate or sitosterol 3-palmatate (1) and sitosterol 3-tetradecanoate or sitosterol 3-myristate (2) in addition to beta sitosterol (3) were isolated and characterized. Compounds 1 and 2 administered at 3 µmol/kg (p.o.) produced anti-inflammatory activity (P < 0.0001) of 31.02 and 39.14% respectively, in addition to arthritic score index (P < 0.0001) of 1.600 ± 0.2449 and 1.400 ± 0.2449 against CFA-induced arthritis which are equivalent to those of the standard drug, diclofenac sodium (DS), 3 µmol/kg (p.o.), (30.79% anti-inflammatory activity and 1.800 ± 0.3742 arthritic score index). The compounds produced similar anti-inflammatory effects as DS. Also, radiographical and histopathological studies showed that, the compounds and DS protected against bone destruction, inflammatory cells invasion into interstitial spaces and synovial liner hyperplasia of the joints. This is the first study to report the characterization of the constituents of C. erythrocarpos in addition to anti-arthritic activity of sitosterol 3-palmatate and sitosterol 3-myristate. These results provide the missing link between the chemistry and the pharmacological activities of C. erythrocarpos. The isolates also offer a different class of molecule which could provide alternative treatment for RA.