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Isolation and Bioactivity of Secondary Metabolites from Solid Culture of the Fungus, Alternaria sonchi

1
All-Russian Institute of Plant Protection, Russian Academy of Agricultural Sciences, Pushkin, 196608 Saint-Petersburg, Russia
2
Research Institute of Hygiene, Occupational Pathology and Human Ecology, Federal Medical Biological Agency, p/o Kuz’molovsky, 188663 Saint-Petersburg, Russia
3
G.B. Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch of Russian Academy of Sciences, 690022 Vladivostok, Russia
4
St. Petersburg State University, Universitetsky Av. 26, 198504 St. Petersburg, Russia
*
Author to whom correspondence should be addressed.
Biomolecules 2020, 10(1), 81; https://doi.org/10.3390/biom10010081
Received: 4 December 2019 / Revised: 27 December 2019 / Accepted: 2 January 2020 / Published: 4 January 2020
(This article belongs to the Section Natural and Bio-inspired Molecules)
The fungus, Alternaria sonchi is considered to be a potential agent for the biocontrol of perennial sowthistle (Sonchus arvensis). A new chlorinated xanthone, methyl 8-hydroxy-3-methyl-4-chloro-9-oxo-9H-xanthene-1-carboxylate (1) and a new benzophenone derivative, 5-chloromoniliphenone (2), were isolated together with eleven structurally related compounds (313) from the solid culture of the fungus, which is used for the production of bioherbicidal inoculum of A. sonchi. Their structures were determined by spectroscopic (mostly by NMR and MS) methods. Alternethanoxins A and B, which were reported in A. sonchi earlier, were re-identified as moniliphenone and pinselin, respectively. The isolated compounds were tested for phytotoxic, antimicrobial, insecticidal, cytotoxic and esterase-inhibition activities. They did not demonstrate high phytotoxicity (lesions up to 2.5 mm in diameter/length at a concentration of 2 mg/mL) when tested on leaf disks/segments of perennial sowthistle (Sonchus arvensis) and couch grass (Elytrigia repens). They did not possess acute toxicity to Paramecium caudatum, and showed moderate to low cytotoxicity (IC50 > 25 µg/mL) for U937 and K562 tumor cell lines. However, chloromonilicin and methyl 3,8-dihydroxy-6-methyl-4-chloro-9-oxo-9H-xanthene-1-carboxylate (4) were shown to have antimicrobial properties with MIC 0.5–5 µg/disc. Compound 4 and chloromonilinic acid B were found to have contact insecticidal activity to wheat aphid (Schizaphis graminum) at 1 mg/mL. Compounds 2 and methyl 3,8-dihydroxy-6-methyl-9-oxo-9H-xanthene-1-carboxylate displayed selective carboxylesterase inhibition activity at concentration of 100 µg/mL. Therefore, the waste solid substrate for production of A. sonchi spores can be re-utilized for the isolation of a number of valuable natural products. View Full-Text
Keywords: Alternaria sonchi; perennial sowthistle; mycoherbicide; fungal xanthones; alternethanoxins; use of waste substrate Alternaria sonchi; perennial sowthistle; mycoherbicide; fungal xanthones; alternethanoxins; use of waste substrate
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Dalinova, A.; Chisty, L.; Kochura, D.; Garnyuk, V.; Petrova, M.; Prokofieva, D.; Yurchenko, A.; Dubovik, V.; Ivanov, A.; Smirnov, S.; Zolotarev, A.; Berestetskiy, A. Isolation and Bioactivity of Secondary Metabolites from Solid Culture of the Fungus, Alternaria sonchi. Biomolecules 2020, 10, 81.

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