New seco-abietane diterpenoids, phenylethanoid, and anti-inflammatory constituents from Callicarpa pilosissima

Callicarpa pilosissima (Verbenaceae) is an endemic evergreen shrub that grows in low-to-medium-altitude forests throughout Taiwan. Phenylethanoid glycosides [1,2,3], clerodane diterpenes [4], triperpenes [5], and their derivatives are widely distributed in plants of the genus Callicarpa. Many of these compounds exhibit antioxidant [1], neuroprotective [2], and cytotoxic [4,5] activities. However, the chemical constituents and biological activities of this plant have never been studied. In our studies on the anti-inflammatory constituents of Formosan plants, many species have been screened for in vitro anti-inflammatory activity, and C. pilosissima has been found to be one of the active species. Investigation on EtOAc-soluble fraction of the leaves and twigs of Callicarpa pilosissima has led to the isolation of three new compounds, including two new seco-abietane diterpenoids, callicarpin (1) and 11,12-dehydrocallicarpin (2), and a new phenylethanoid, 4-hydroxyphenethyl tetradecanoate (3), together with five known compounds, including two diterpenoids, 3-oxo-abicta-8,11,13-triene (4) and margocin (5), a fatty acid, stearic acid (6), and two steroids, β-sitosterol (7) and stigmasterol (8). The structures of these new compounds were determined through spectroscopic analyses including 2D-NMR data. This work describes the structural elucidation of these new compounds and the anti-inflammatory activities of the isolates.

Acknowledgements: This work was supported by grant from the National Science Council of the Republic of China.

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