J. Phytopathology 125, 97—109 (1989) © 1989 Paul Parey Scientific Publishers, Berlin and Hamburg ISSN 0931-1785 Department of Botany, University of Peradeniya, Sri Lanka Biological Activity of Four Antifungal Compounds in Immature Avocado S. SiVANATHAN and N. K. B. ADIKARAM Authors' address; Department of Botany, University of Peradeniya, Peradeniya, Sri Lanka. Witb 6 figures Received Oetober 27, 1987; aeeepted June 16, 1988 Abstract Anthracnose caused by Colletotriebum gloeosporioides in ripe avocados originates as latent infections in the immature fruits. Concentrated ether extract of the peel of apparently healthy, immature avocados when bioassayed on thin layer chromatographic plates with conidia of either Cladosporium eladosporioides or C. gloeosporioides produced four inhibition areas at Rf 0.30, 0.32, 0.70 and 0.75 (these were denoted as AvIV, AvIII, AvII and AvI respectively). A hot chloroform extract was partitioned on a silica gel column and the four antifungal compounds were separated. Spectroscopic data revealed that one of these compounds, AvII, was similar to cis-l-acetoxy-2- hydroxy-4-oxo-heneicosa-12,15-diene and another (AvIV) was a long chain saturated compound comprising hydroxyl group(s) having molecular weight of 268. Toxicity of AvII to C gloeosporioides was 2 times that of AvIV and 6.5 and 7.5 times that of AvIII and AvI respectively. The amounts of these four antifungal compounds increased gradually during fruit development and reached their maxima at harvest. The concentration of AvI, AvII, AvIII and AvIV was 1300, 920, 1050 and 780 ,ug/g fresh peel respectively in the fruit at harvesting maturity. The amount of AvII and AvIV decreased to 53 and 64 f(g/g fresh peel respectively in the fruit at the ripe stage at which neither AvI nor AvIII was detected. This took place in coincidence with the onset of progressive lesion development by the fungus. Zusammenfassung Biologische Aktivitat von vier antipilzlichen Substanzen in unreifen Avocados Eine Anthraknose, die durch Colletotriehum gloeosporioides verursacht ist, geht in reifen Avocadofruchten von latenten Infektionen der unreifen Fruchte aus. Konzentrierter Atherextrakt der Schale aus scheinbar gesunden, unreifen Avocadofruchten, der nach diinnschichtchromatographischer Trennung mit Konidien von entweder Cladosporium eladosporioides oder C. gloeosporioides entwik- kelt wurde, zeigte vier Hemmzonen mit Rf-Werten 0,30, 0,32, 0,70 und 0,75 (die als AvIV, AvIII, AvII bzw. AvI bezeichnet wurden). Nach einer heifien Chloroformextraktion wurde der Extrakt an einer Silicagelsaule fraktioniert, und die vier fungiziden Verbindungen getrennt. Spektroskopische Analyse ergab, dafi die Verbindung AvII eine Ahnlicbkcit mit cis-l-acetoxy-2-hydroxy-4-oxo- U.S. Copyright Clearance Center Code Statement: 0 9 3 1-1 7 8 5 / 8 9 / 2 5 0 2 - 0 0 9 7 $ 0 2 . 5 0 / 0