Orlandin: a nontoxic fungal metabolite with plant growth inhibiting properties

Abstract

many trees were diseased, no gross anatomical or physiological differences were observed on leaves infected with A. niger. Nevertheless, the organism was examined for plant growth regulator metabolites. Subsequent isolation and extraction of the fungus, from shredded wheat cultures, yielded a crystalline metabolite that inhibited the growth of etiolated wheat coleoptile sections. The metabolite, when compared with the plant growth inhibitor (±)-abscisic acid was as active at 10™3 and 10™4 M in the coleoptile bioassay, but was less active at 10"5 M. (+)-Abscisic acid has been found in many higher plants (Addicott and Lyon, 1969;Milborrow, 1974) and was initially isolated from immature cotton fruits, Gossypium hirsutum L. (Ohkuma et al., 1963) and sycamore leaves, Acer pseudoplatanus L. (Cornforth et al., 1965). Chemical and physical analyses showed that the new metabolite was bis [8,8'-(7-hydroxy-4-methoxy-5-methylcoumarin) ] which we have given the trivial name orlandin (I) (Figure 1).The simple coumarins have shown a wide range of growth regulating responses in plants from growth promotion to growth inhibition depending on the plant species or plant part treated (Mayer and Poljakoff-Mayber, 1961).

Confirmation of the polyketide origin of kotanin by incorporation of [1,2-13C2]acetate

“…Thin-layer chromatography (tlc) was done on precoated sheets of silica gel (Macherey-Nagel Polygram Sil G/UV254r 0.25 mm) with MeOHI CHC1, (2:98 v/v) as solvent and uv light (254 nm) and (or) vanillin (0.5% in 60% phosphoric acid) for detection. Column chromatography was performed as described by Cutler et al (6). Melting points were determined on a Kofler hot stage and are uncorrected.…”

“…This compound had not been reported previously as a from Fusarium martii (2), colletruncoic acid methyl ester (2) metabolite of A. niger. Other fractions from the chromatogram from Colletotrichum truncatum (3), kotanin (3) and demethyl kotanin (4) from Aspergillus clavatus (4,5), orlandin (5) from A. niger (6), siderin (6), the monomer of kotanin, from A. variecolor (7,8), and the desertorins A, B, and C (7-9, respectively) from Emericella desertorurn ( A . nidulans group) (9).…”

Chemodiversity in the genus Aspergillus

“…Species in section Flavi, A. alliaceus and A. flavus produce isokotanins and aflavarins (TePaske et al 1992;Laakso et al 1994), A. clavatus in section Clavati and A. niger in section Nigri produce kotanins (Cutler et al 1979;Varga et al 2007c Fig. 12 Some emodin-derived secondary metabolites in different sections of Aspergillus.…”

Transcriptome Analysis of Aspergillus flavus Reveals veA -Dependent Regulation of Secondary Metabolite Gene Clusters, Including the Novel Aflavarin Cluster

“…A large number of natural biaryl compounds have been extensively described in plants, fungi, and bacteria (52)(53)(54). In particular, fungi of the genus Aspergillus have been shown to be capable of producing a diverse class of bicoumarins, including C8-C8=-linked bicoumarins (e.g., kotanin and orlandin [39,55]), C6-C8=-linked bicoumarins (e.g., desertorin A-C [56]), C6-C6=-linked bicoumarins (e.g., isokotanin A-C [57]), and C3-C3=-linked bicoumarins (e.g., bicoumanigrin [58]). All these metabolites share the C-C biaryl axis as a characteristic structural feature.…”