Unusual antimicrobial compounds from Aeollanthus buchnerianus.

Using bioassay guided isolation, three novel 12 carbon polyoxygenated fatty acids and a novel abietane diterpene have been isolated from the chloroform extract of aerial parts of Aeollanthus buchnerianus (Lamiaceae). Rigorous spectroscopic methods were used for compound identification. (Z,Z)-8zeta-acetoxy-5zeta-hydroxydodeca-2,6-dienoic acid and (Z,Z)-5zeta, 8zeta-dihydroxydodeca-2,6-dienoic acid inhibited the spore germination of Cladosporium cucumerinum (both with Minimum Inhibitory Dose (MID) values of 1 microgram) and Aspergillus niger (MID 5 and 25 microgram respectively). Further, they also reduced the hyphal growth of Pythium ultimum. (Z)-5zeta-hydroxy-6zeta,7zeta,8zeta-triacetox ydodeca-2-dienoic acid exhibited short term inhibition of the growth of Cladosporium cucumerinum. The novel abietane diterpenoid, (rel)-14alpha-acetoxyabiet-7-en-18-oic acid inhibited the growth of the gram positive bacteria Bacillus subtilis, Staphylococcus aureus and Streptomyces scabies (MIC values 80, 20 and 20 micrograms ml(-1) respectively).