The Phytotoxin Myrigalone A Triggers a Phased Detoxification Programme and Inhibits Seed Germination via Multiple Mechanisms including Interference with Auxin Homeostasis.

Molecular responses of plants to natural phytotoxins comprise more general and compound-specific mechanisms. How phytotoxic chalcones and other flavonoids inhibit seedling growth was widely studied, but how they interfere with seed germination is largely unknown. The dihydrochalcone and putative allelochemical myrigalone A (MyA) inhibits seed germination and seedling growth.

Synthesis and antifungal activity of novel streptochlorin analogues.

Streptochlorin, first isolated as a new antibiotic in 1988 from the lipophilic extracts of the mycelium of a Streptomyces sp, is an indole natural products with a variety of biological activities. Based on the methods developed for the synthesis of pimprinine in our laboratory, we have synthesized a series of indole-modified streptochlorin analogues and measured their activities against seven phytopathogenic fungi. Some of the analogues displayed good activity in the primary assays, and the seven compounds 10b, 10c, 11e, 13e, 21, 22c and 22e (shown in Figure 1) were identified as the most promising candidates for further study.

Synthesis and antifungal activity of 3-(1,3,4-oxadiazol-5-yl)-indoles and 3-(1,3,4-oxadiazol-5-yl)methyl-indoles.

On the basis of the principle of combination of active structural moieties, a modified and efficient synthetic method for three series of novel indole-based 1,3,4-oxadiazoles is described. Bioassays conducted at Syngenta showed that several of the synthesized compounds exhibit higher antifungal activity than pimprinine, the natural product which inspired this synthesis. Two main structural alterations were found to broaden the spectrum of biological activity in most cases.

PPARγ agonist from Chromolaena odorata.

A phytochemical investigation of Chromolaena odorata resulted in the isolation of five new compounds, 5aα,6,9,9aβ,10-pentahydro-10β-hydroxy-7-methylanthra[1,2-d][1,3]dioxol-5-one (1), 1,2-methylenedioxy-6-methylanthraquinone (2), 3-hydroxy-1,2,4-trimethoxy-6-methylanthraquinone (3), 3-hydroxy-1,2-dimethoxy-6-methylanthraquinone (4), and 7-methoxy-7-epi-medioresinol (5), together with 12 known compounds, odoratin (6), 3β-acetyloleanolic acid (7), ursolic acid (8), ombuin (9), 4,2'-dihydroxy-4',5',6'-trimethoxychalcone (10), (-)-pinoresinol (11), austrocortinin (12), tianshic acid (13), cleomiscosin D (14), (-)-medioresinol (15), (-)-syringaresinol (16), and cleomiscosin A (17). All the compounds were evaluated for their PPARγ transactivation activity, and compound 6 showed moderate activity with an EC(50) value of 3.10 μM.

Design, synthesis and fungicidal activity of novel sclerotiorin derivatives.

Sclerotiorin, a chlorine-containing azaphilone-type natural product, was first isolated from Penicillium sclerotiorum and has been reported to exhibit weak fungicidal activity. Optimization of the substituents at the 3- and 5-positions of the sclerotiorin framework was investigated with the aim of discovering novel fungicides with improved activity. The design of sclerotiorin analogues involved replacing the diene side chain with a phenyl group or an aromatic- or heteroaromatic-containing aliphatic side chain.

Synthesis and fungicidal activity of novel pimprinine analogues.

A simple and efficient synthetic protocol for 5-(3-indolyl)-oxazoles has been developed and further used to synthesize a series of novel analogues of natural product pimprinine. All new compounds were identified by (1)H NMR, high resolution mass spectrometry, and the structures of 10 and 18o were further confirmed by X-ray crystallographic diffraction analysis. Bioassay conducted at Syngenta showed that several of the synthesized compounds exhibited fungicidal activity.

Synthesis and antifungal activity of novel sclerotiorin analogues.

Sclerotiorin 1, first isolated from Penicillium sclerotiorum, has weak antifungal activity and belongs to the azaphilone-type family of natural products. Several series of sclerotiorin analogues were designed and synthesized with the aim of discovering novel fungicides with improved activity. The syntheses involved two key steps, cycloisomerization and then oxidation, and used a simple and efficient Sonogashira cross-coupling reaction to construct the required functionalized precursor.

Further Daphniphyllum alkaloids with insecticidal activity from the bark of Daphniphyllum macropodum M(IQ).

Two new Daphniphyllum alkaloids, macropodumines J and K (1 and 2, resp.), together with six known structurally related alkaloids, 3-8, were isolated from the bark of Daphniphyllum macropodum M(IQ). The structures of the new compounds 1 and 2 were elucidated on the basis of a comprehensive analysis of their spectroscopic and chemical data.

Serialynic acid, a new phenol with an isopentenyne side chain from Antrodia serialis.

A new phenolic compound serialynic acid was isolated from an agar culture of the basidiomycete Antrodia serialis, through bioactivity-guided fractionations. It showed weak growth inhibitory activity towards phytopathogenic fungi and a dose-independent anti-Pythium graminicola activity.

Insect antifeedant furanocoumarins from Tetradium daniellii.

The dried fruits of Tetradium daniellii yielded a new linear furanocoumarin, 5-(6-hydroxy-3,7-dimethylocta-2,7-dienyloxy)psoralen, together with six other structurally related furanocoumarins. A similar chemical profile was recorded by HPLC analysis of a fragment of T. daniellii fruit obtained from an historic herbarium voucher specimen collected in September 1917 during an expedition to Yunnan province, China.