Advances in chemical synthesis reveal rare natural product with potent pain-killing properties

Scientists from the Florida campus of The Scripps Research Institute have for the first time accomplished a laboratory synthesis of a rare natural product isolated from the bark of a plant widely employed in traditional medicine.

This advance may provide the scientific foundation to develop an effective alternative to commonly prescribed narcotic pain treatments.

The study, published 23 May 2011, in an advanced online edition of the journal Nature Chemistry, defines a chemical means to access meaningful quantities of the rare natural product conolidine. Based on data from mouse models, the study also suggests that synthetic conolidine is a potent analgesic as effective as morphine in alleviating inflammatory and acute pain, with few, if any, side effects.

In recent years, there has been significant interest in developing alternatives to opiate-based pain medications such as morphine. While widely prescribed for pain, morphine has a number of adverse side effects that range from the unpleasant to the lethal, including nausea, chronic constipation, addiction, and breathing depression.

The rare natural product central to the study is derived from the bark of a widely grown tropical flowering plant Tabernaemontana divaricata (also known as crepe jasmine). Long part of traditional medicine in China, Thailand, and India, extract from the leaves has been used as an anti-inflammatory applied to wounds, while the root has been chewed to fight the pain of toothache. Other parts of the plant have been used to treat skin diseases and cancer.

Conolidine belongs to a larger class of natural products, called C5-nor stemmadenines, members of which have been described as opioid analgesics, despite a substantial discrepancy between potent in vivo analgesic properties and low affinity to opiate receptors. Conolidine is an exceptionally rare member of this family for which no therapeutically relevant properties had ever been described. Despite the potential value of conolidine and related C5-nor stemmadenines as leads for therapeutics, efficient methods to prepare these molecules were lacking.