Recent Advances in Alternaria Phytotoxins: A Review of Their Occurrence, Structure, Bioactivity, and Biosynthesis

Abstract

Alternaria is a ubiquitous fungal genus in many ecosystems, consisting of species and strains that can be saprophytic, endophytic, or pathogenic to plants or animals, including humans. Alternaria species can produce a variety of secondary metabolites (SMs), especially low molecular weight toxins. Based on the characteristics of host plant susceptibility or resistance to the toxin, Alternaria phytotoxins are classified into host-selective toxins (HSTs) and non-host-selective toxins (NHSTs). These Alternaria toxins exhibit a variety of biological activities such as phytotoxic, cytotoxic, and antimicrobial properties. Generally, HSTs are toxic to host plants and can cause severe economic losses. Some NHSTs such as alternariol, altenariol methyl-ether, and altertoxins also show high cytotoxic and mutagenic activities in the exposed human or other vertebrate species. Thus, Alternaria toxins are meaningful for drug and pesticide development. For example, AAL-toxin, maculosin, tentoxin, and tenuazonic acid have potential to be developed as bioherbicides due to their excellent herbicidal activity. Like altersolanol A, bostrycin, and brefeldin A, they exhibit anticancer activity, and ATX V shows high activity to inhibit the HIV-1 virus. This review focuses on the classification, chemical structure, occurrence, bioactivity, and biosynthesis of the major Alternaria phytotoxins, including 30 HSTs and 50 NHSTs discovered to date.

The novel distribution of intracellular and extracellular flavonoids produced by Aspergillus sp. Gbtc 2, an endophytic fungus from Ginkgo biloba root

“…However, the flavonoid content in Ginkgo extract is extremely low, which is challenging to meet the growing market demand ( Isah, 2015 ). Due to the long-term co-evolution, plants and endophytic fungi may share some functional enzymes in the metabolic process ( Teimoori-Boghsani et al, 2019 ; Wang H. et al, 2022 ). Endophytic fungi have been shown to indirectly or directly synthesize some intermediates of host plants ( Jia et al, 2016 ; Ferreira et al, 2021 ), participating in plant signal pathways and assisting plants in completing physiological and biochemical processes ( Shymanovich et al, 2015 ).…”

Overexpression of transcriptional regulator and tailoring enzyme leads to the discovery of anti-inflammatory meroterpenoids from marine-derived fungus Alternaria alternata JJY-32

“…The genus Alternaria produces a broad diversity of secondary metabolites with a large range of bioactivities (Bräse et al, 2009;Lou et al, 2013;Lou et al, 2013;Abdessemed et al, 2021;Wang et al, 2022). ACTG toxins are a family of meroterpenoids mainly discovered from Alternaria alternata and Alternaria citri.…”

Secondary metabolites of Alternaria: A comprehensive review of chemical diversity and pharmacological properties

“…Alternaria fungus is a widespread dark fungus, belonging to classes Ascomycota, Dothideomycetes, Pleosporales, and Pleosporaceae (Feng and Sun, 2020). The fungal genus Alternaria is a ubiquitous group growing in diverse ecosystems worldwide as a parasitic, saprophytic, or endophytic species (Wang et al, 2022). Of these, Alternaria alternata, Alternaria brassicicola, Alternaria penicillata, Alternaria cetera, Alternaria alternantherae, and another 28 groups are ubiquitous (Feng and Sun, 2020;Li et al, 2021;Wang et al, 2022).…”

“…The fungal genus Alternaria is a ubiquitous group growing in diverse ecosystems worldwide as a parasitic, saprophytic, or endophytic species (Wang et al, 2022). Of these, Alternaria alternata, Alternaria brassicicola, Alternaria penicillata, Alternaria cetera, Alternaria alternantherae, and another 28 groups are ubiquitous (Feng and Sun, 2020;Li et al, 2021;Wang et al, 2022). Alternaria species can produce a variety of secondary metabolites.…”

“…These metabolites mainly include polyketides, nitrogen-containing compounds, quinones, terpenes, and other compounds (Yamada et al, 2019;Li et al, 2020a;Tian et al, 2021). A large number of potentially bioactive molecules have been found, with intriguing structural skeletons and remarkable activities (Lou et al, 2013;Wang et al, 2022). Bioactive metabolites secreted by Alternaria fungi often exhibit excellent pharmacological potential, such as anticancer, antibacterial, antioxidant, and enzyme inhibitory effects Dalinova et al, 2020;Mahmoud et al, 2021;Tian et al, 2021).…”