Isolation and structure determination of allopteridic acids A–C and allokutzmicin from an unexplored actinomycete of the genus Allokutzneria

Two classes of new polyketides, allopteridic acids A–C ( 1 – 3 ) and allokutzmicin ( 4 ), were isolated from the culture extract of an actinomycete of the genus Allokutzneria . The structures of 1 – 4 were elucidated through the interpretation of NMR and MS analytical data. Compounds 1 – 3 possess the same carbon skeleton with pteridic acids but their monocyclic core structures are distinct from the spiro-bicyclic acetal structures of pteridic acids. Compound 4 is a linear polyketide of an unprecedented class, featured by a guanidino-terminus and an epoxide modification. Compounds 1 – 3 promoted the root elongation of germinated lettuce seeds by ca . 10–40% at 1~10 μM whereas 4 retarded the seed growth. Compound 4 exhibited weak antimicrobial activity against Candida albicans with MIC 25 μg mL −1 .