St. John's Wort seed and feverfew flower extracts relieve painful diabetic neuropathy in a rat model of diabetes.

Painful diabetic peripheral neuropathy (DPN) is a common complication of diabetes and the few approved therapies for the management of pain have limited efficacy and side effects. With the aim to explore and develop new pharmacological treatments, we investigated the antihyperalgesic properties of St. John's Wort (SJW) and feverfew in streptozotocin (STZ)-diabetic rats. Acute administration of a SJW seed extract reversed mechanical hyperalgesia with a prolonged effect. A SJW extract obtained from the aerial portion of the plant and a feverfew flower extract partially relieved neuropathic pain whereas a feverfew leaf extract was ineffective. The antihyperalgesic efficacy of these herbal drugs was comparable to that of clinically used antihyperalgesic drugs (carbamazepine, lamotrigine, l-acetyl-levocarnitine). Further examinations of SJW and feverfew composition revealed that hyperforin and hypericin might be responsible for the antihyperalgesic properties of SJW whereas the efficacy of feverfew seems to be related to the presence of parthenolide. Rats undergoing treatment with SJW and feverfew did not show any behavioral side effect or sign of altered locomotor activity. Our results suggest that SJW and feverfew extracts may become new therapeutic perspectives for painful DPN.