Turmeric (Curcuma longa L., Zingiberaceae) rhizomes contain two classes of secondary metabolites,
curcuminoids and the less well-studied essential oils. Having previously identified potent antiarthritic
effects of the curcuminoids in turmeric extracts in an animal model of rheumatoid arthritis
(RA), studies were undertaken to determine whether the turmeric essential oils (TEO) were also joint
protective using the same experimental model. Crude or refined TEO extracts dramatically inhibited
joint swelling (90-100% inhibition) in female rats with streptococcal cell wall (SCW)-induced
arthritis when extracts were administered via intraperitoneal injection to maximize uniform delivery.
However, this anti-arthritic effect was accompanied by significant morbidity and mortality. Oral
administration of a 20-fold higher dose TEO was non-toxic, but only mildly joint-protective (20%
inhibition). These results do not support the isolated use of TEO for arthritis treatment, but, instead,
identify potential safety concerns in vertebrates exposed to TEO.