Effects of rosmarinic acid on an experimental model of painful diabetic neuropathy in rats

Context: Diabetic neuropathic (DN) pain is one of the diabetes complications. Rosmarinic acid (RA), a natural phenol antioxidant, shows some biological activities, including anti-inflammatory, analgesic, and anti-diabetic effects.

Objectives: We investigated the efficacy of RA administration (10 and 30?mg/kg) on streptozotocin (STZ)-induced neuropathy in rats.

Material and methods: The animals received saline or RA (10 and 30?mg/kg, p.o.; once daily) for 8 weeks. DN was evaluated by the tail flick (TF) method, formalin test, and tactile allodynia. At the end, all rats were weighed and underwent plasma glucose measurement.

Results: There was an increase in licking time during both formalin test phases in diabetic animals (138.5?±?10.7 and 448.7?±?2.6?s) that was decreased by RA10?mg/kg (103.5?±?7.5 and 284.4?±?19?s) and RA 30?mg/kg (81.8?±?11 and 192.7?±?14?s). RA 30?mg/kg caused anti-nociception during the early phase in treated controls (52.1?±?6?s) than untreated controls (99.4?±?5.9?s). The TF latency in diabetics (2.9?±?0.1?s) was increased in RA10 and 30?mg/kg treated diabetics (5.3?±?0.4 and 6?±?0.86?s). The paw withdrawal threshold (PWT) of the diabetics (3.6?±?0.7?g) was increased after RA 10 and 30?mg/kg (13.8?±?0.3 and 14?±?0.4?g) treatment. RA did not induce a significant change in body weight and plasma glucose of rats.

Conclusion: RA showed efficacy in amelioration of some aspects of DN. Therefore, RA makes a good candidate for DN treatment in clinical studies.