Chemistry of leaves, bark, and essential oils from Ocotea diospyrifolia and anti-inflammatory activity – Dual inhibition of edema and neutrophil recruitment

Abstract

Species from the Ocotea genus have shown scientific evidence of anti-inflammatory activity through a promising mechanism of action. This study is the first in vivo evaluation of the anti-inflammatory potential and mechanism of action of extracts and essential oils from the leaves and bark of O. diospyrifolia. We isolated and identified compounds from the leaf and bark extracts and chemically characterized these extracts by ultra high-performance liquid chromatography–high-resolution mass spectrometry (UPLC-HRMS). Additionally, the essential oils were characterized by gas chromatography–mass spectrometry (GC–MS). Nine compounds (1-9) were isolated; among them, a new compound (9) was elucidated as 6aS,7S-(-)-11-hydroxy-7-methoxy-1,2-methylenedioxy-aporphine, named as diospirifoline. The aporphine substitution pattern found in diospirifoline, with substitution at C-7, was identified for first time in the Ocotea genus. Mururin A(1) and salsoline (5) were also isolated for the first time in this genus. The biosynthetically linked alkaloids coclaurine (7), reticuline (6), and isoboldine (8) were found to be 6aR-(-) isomers, which is different from the 6aS-(+) isomers that are most often found in other Ocotea spp. UPLC-HRMS analysis detected various classes of compounds in the leaf and bark extracts, such as flavonolignans, flavonoids, chlorogenic acids, alkaloids, and many other unidentified compounds. The GC–MS analysis revealed that both leaf and bark essential oils contained α-phellandrene as the major compound and that the chemotaxonomic marker of the Lauraceae family, the phenylpropanoid safrole, was not detected. Furthermore, some of the compounds identified in the extracts and essential oils have known anti-inflammatory activities, such as 5-caffeoylquinic acid, quercitrin, α-humulene, and (E)-caryophyllene. Indeed, the leaf extract, its ethyl acetate fraction, and the essential oils showed in vivo anti-inflammatory activity through the dual inhibition of edema and neutrophil recruitment, suggesting the inhibition of main inflammatory pathways. This mechanism of action is associated with a better efficacy and safety profile than that of the currently available anti-inflammatory drugs. The extract and essential oils of O. diospyrifolia showed high chemical diversity and a promising anti-inflammatory mechanism of action; thus, clearly indicating that this species should be further investigated.