Sesquiterpenes from the wood of Juniperus lucayana.

Bioassay-guided fractionation of ethanolic extract from the wood of Juniperus lucayana afforded three sesquiterpenes named 3-hydroxypseudowiddran-6(7)-en-4-ol (1), 15-hydroxyallo-cedrol (2) and 12-hydroxywiddrol (3) together with six known sesquiterpenes (4-9) and two known flavonoids (10 and 11). Their structures were established on the basis of comprehensive spectroscopic analyses, including 2D NMR spectroscopy and mass spectrometry. The structures of compounds were identified as 1alpha,4beta,11alpha,11beta-tetramethylbicyclo[5,4,0]undec-6(7)-en-3alpha, 4alpha-diol (1), 4beta-hydroxymethyl-5,5,9beta-trimethyltricyclo[4.3.0.2(1.4)]undecan-3alpha-ol (2) and 4beta-hydroxymethyl-7alpha,11alpha,11beta-trimethylbicyclo [5.4.0]undec-1-en-4alpha-ol (3). The major compounds isolated were evaluated for their antifungal activity against Botrytis cinerea. Widdrol (7) was the most active, reaching the 71% inhibition level on mycelial growth after 6 days.

The antifungal activity of widdrol and its biotransformation by Colletotrichum gloeosporioides (penz.) Penz. & Sacc. and Botrytis cinerea Pers.: Fr.

Widdrol (1) was tested against the necrotrophic plant pathogens Botrytis cinerea and Colletotrichum gloeosporioides. While 1 was found to be inactive against C. gloeosporioides, it showed a selective and effective control of B. cinerea, significantly inhibiting the mycelial growth of the fungus at concentrations of 100 ppm and above. In addition, the biotransformation of 1 by both fungi was studied. Incubation with C. gloeosporioides and B. cinerea afforded four and one biotransformation products (2-6), respectively. Biotransformation with C. gloeosporioides was highly regioselective, yielding for the most part oxidation products at C-10: 10-oxowiddrol (2), 10beta-hydroxywiddrol (3), 10alpha-hydroxywiddrol (4), and 14alpha-hydroxywiddrol (5). The structures of all products were determined on the basis of their spectroscopic data, including coupling constants, two-dimensional NMR analysis (heteronuclear multiple quantum coherence, heteronuclear multiple bond correlation, and nuclear Overhauser enhancement spectroscopy), and nuclear Overhauser effect. The biotransformation products were then tested against B. cinerea and found to be inactive. These results shed further light on the structural modifications, which may be necessary to develop selective fungal control agents against B. cinerea.