Phytochemistry and antifungal properties of the newly discovered tree Pleodendron costaricense

Gas chromatography analysis of the essential oils of leaves and bark collected from the newly discovered tree Pleodendron costaricense identified alpha-pinene, beta-pinene, beta-myrcene, beta-thujene, and beta-caryophyllene as their major constituents. Phytochemical analysis of P. costaricense parts led to the isolation and identification of delta-tocotrienol, beta-sitosterol, four known drimane-type sesquiterpenes, cinnamodial (1), cinnamosmolide (2), polygodial (3), and mukaadial (4), and two new compounds, a drimane-type sesquiterpene, parritadial (5), and an eremophilane-type sesquiterpene, pleodendione (6). Antifungal assays with the two major compounds, 1 and 2, were carried out, and results showed a high activity of 1 against Alternaria alternata (MIC = 3.9 microg/mL), Candida albicans azole-resistant strain D10, and Wangiella dermatitides (MICs = 15.6 microg/mL). Compound 2 showed less potent antifungal activities than 1 but was more effective against Candida albicans azole-resistant strain CN1A (MIC = 23.4 microg/mL) and Pseudallescheria boydii (MIC = 78.1 microg/mL). A combination of the dialdehyde sesquiterpenes with dillapiol showed a synergistic antifungal effect with 1 and an additive effect with 4 and 5.