Topical anti-inflammatory activity of boropinic acid and of its natural and semi-synthetic derivatives

Boropinic acid (R=OCH₃) is an isopentenyloxycinnamic acid isolated from the roots of Boronia pinnata Sm., an Australian shrub belonging to the family of Rutaceae [1]. In a recent study we have shown that this natural compound exerts a significant in vitro inhibitory activity on soybean 5-lipoxygenase and, by means of molecular techniques, put in evidence its ability to strongly bind to the active site of this enzyme [2].

Basing on these findings, we verified the topical anti-inflammatory activity of boropinic acid and of its eight natural and semi-synthetic derivatives, resulting from the substitution of the methoxy group in position 8, following the environmental friendly route that we already reported [2]. Each compound was evaluated for its ability to inhibit the Croton oil induced-ear oedema in mice [3], in comparison to equimolar doses of nordihydroguaiaretic acid, a known lipoxygenase inhibitor, and of the non steroidal anti-inflammatory drug indomethacin. Almost all the compounds (0.3µmol/cm²) provoked significant oedema inhibition (from 19 to 78%), comparable or higher than that of nordihydroguaiaretic acid (36% oedema inhibition) and of indomethacin (62% inhibition).

References: 1. Ito, A. et al. (2000)J. Nat. Prod. 63:1344–1348. 2. Curini, M. et al. (2006) Nat. Prod. Commun. 1:1141–1145. 3. Tubaro, A. et al. (1985) Agents Actions 17: 347–349.