Acute effect of Capparis spinosa root extracts on rat articular pain.

ETHNOPHARMACOLOGICAL RELEVANCE: Capparis spinosa L. originates from dry regions of Asia and Mediterranean basin. In traditional medicine of these areas, infusions from caper root are considered to be beneficial for the treatment of rheumatism, gout and against abdominal pains. AIM OF THE STUDY: To evaluate the pain relieving properties of a Syrian cultivar of Capparis spinosa roots in rat models of osteoarthritis and rheumatoid arthritis. MATERIALS AND METHODS: Decoction (DEC) and hydroalcoholic extract (EtH2O) were obtained from powdered roots; the latter was further separated in CH2Cl2 and aqueous (H2O-Res) fractions. The extracts were characterized in terms of spermidine alkaloids by HPLC/DAD/MS and stachydrine by NMR. Different amount of free and glycosilated forms of capparispine and analogues (from 0.5% w/w for DEC up to 7.6% w/w for CH2Cl2 fraction) were detected. Rat models of rheumatoid arthritis and osteoarthritis were induced by the intra-articular administration of Complete Freund's Adjuvant (CFA) or monosodium iodoacetate (MIA), respectively. RESULTS: Fourteenth days after CFA or MIA injection, the different preparations of Capparis spinosa (3, 30, 100 and 300mgkg-1) were acutely administered p.o.. Powdered roots (300mgkg-1), DEC (100mgkg-1), and EtH2O (300mgkg-1) significantly reduced hypersensitivity to mechanical noxious stimuli as well as spontaneous pain evaluated as hind limb bearing alterations in both models. The CH2Cl2 and the H2O-Res (30mgkg-1) were the most potent in reverting pain threshold alterations despite the different content of free alkaloids. CONCLUSIONS: Capparis spinosa extracts relieved pain related to rheumatoid arthritis and osteoarthritis after single administration. A synergistic effect due to a specific "phytochemical mixture" is suggested.