Natural products as a gold mine for arthritis treatment.

Arthritis, an inflammation of the joints, is usually a chronic disease that results from dysregulation of pro-inflammatory cytokines (e.g. tumour necrosis factor and interleukin-1beta) and pro-inflammatory enzymes that mediate the production of prostaglandins (e.g. cyclooxygenase-2) and leukotrienes (e.g. lipooxygenase), together with the expression of adhesion molecules and matrix metalloproteinases, and hyperproliferation of synovial fibroblasts. All of these factors are regulated by the activation of the transcription factor nuclear factor-kappaB. Thus, agents that suppress the expression of tumour necrosis factor-alpha, interleukin-1beta, cyclooxygenase-2, lipooxygenase, matrix metalloproteinases or adhesion molecules, or suppress the activation of NF-kappaB, all have potential for the treatment of arthritis. Numerous agents derived from plants can suppress these cell signaling intermediates, including curcumin (from turmeric), resveratrol (red grapes, cranberries and peanuts), tea polyphenols, genistein (soy), quercetin (onions), silymarin (artichoke), guggulsterone (guggul), boswellic acid (salai guggul) and withanolides (ashwagandha). Indeed, several preclinical and clinical studies suggest that these agents have potential for arthritis treatment. Although gold compounds are no longer employed for the treatment of arthritis, the large number of inexpensive natural products that can modulate inflammatory responses, but lack side effects, constitute 'goldmines' for the treatment of arthritis.