Two kaurane diterpenes, namely cafestol (1) and kahweol (2), were isolated from hydrolyzed fraction of the fixed oil of Ethiopian Coffea arabica unroasted beans, using AgNO3-impregnated silica gel chromatography. In addition, cafestol palmitate (3) and kahweol palmitate (4), the two natural diterpene esters of C. arabica, were also synthesized. Compounds 1–4 were evaluated for anti-inflammatory activity using cyclooxygenase-2 (COX-2), cell aggregation, cell proliferation, cell adhesion, iNOS and antioxidant assays. The COX-2 inhibitory activity of cafestol (1) was found to be 20-fold more potent than kahweol (2) (IC50 value 0.25 μg/mL vs. 5.0 μg/mL), while compounds 3 and 4 were weakly active. The isolation and structure elucidation of the diterpenes 1 and 2, preparation of compounds 3 and 4, and their biological activities are presented in this paper.
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