Anti-inflammatory diterpenoids and other secondary metabolites from Dodonaea polyandra; a traditional medicine used by Kaanju people in North Eastern Australia

Collaborative research guided by the traditional Indigenous knowledge of Northern Kaanju people, Cape York Peninsula, Australia has recently led to the isolation of four new clerodane diterpenoids from the leaves of Dodonaea polyandra (Sapindaceae). These compounds have shown high levels of anti-inflammatory activity in a TPA mouse ear oedema model of inflammation. Dose-response studies revealed compound CS004 (below) was the most potent of these displaying a linear dose-response relationship.

Fig.1: CS004

Percentage inhibition of oedema for this compound ranged from 44 to 85% over the dose range 0.022 to 1.77µmol. The maximum percentage of 85% was comparable at an equimolar dose to the known synthetic steroid betamethasone (90%). The dose-response profiles of the other diterpenoids isolated which are structural analogues of CS004 were also evaluated, however the dose-response characteristics of these compounds were found to be non-linear, with a tendency towards being U-shaped. Additional chemical investigations of the same plant revealed the presence of some flavonoid constituents. These findings add Western scientific evidence supporting the traditional use of the plant in traditional Northern Kaanju medicine.