Fungal phytotoxic secondary metabolites are poisonous substances to plants produced by fungi through naturally occurring biochemical reactions. These metabolites exhibit a high level of diversity in their properties, such as structures, phytotoxic activities, and modes of toxicity. They are mainly isolated from phytopathogenic fungal species in the genera of Alternaria, Botrytis, Colletotrichum, Fusarium, Helminthosporium, and Phoma. Phytotoxins are either host specific or non-host specific phytotoxins. Up to now, at least 545 fungal phytotoxic secondary metabolites, including 207 polyketides, 46 phenols and phenolic acids, 135 terpenoids, 146 nitrogen-containing metabolites, and 11 others, have been reported. Among them, aromatic polyketides and sesquiterpenoids are the main phytotoxic compounds. This review summarizes their chemical structures, sources, and phytotoxic activities. We also discuss their phytotoxic mechanisms and structure–activity relationships to lay the foundation for the future development and application of these promising metabolites as herbicides.

Sorbicillinoids are a family of hexaketide metabolites with a characteristic sorbyl side chain residue. Sixty-nine sorbicillinoids from fungi, newly identified from 2016 to 2021, are summarized in this review, including their structures and bioactivities. They are classified into monomeric, dimeric, trimeric, and hybrid sorbicillinoids according to their basic structural features, with the main groups comprising both monomeric and dimeric sorbicillinoids. Some of the identified sorbicillinoids have special structures such as ustilobisorbicillinol A, and sorbicillasins A and B. The majority of sorbicillinoids have been reported from fungi genera such as Acremonium, Penicillium, Trichoderma, and Ustilaginoidea, with some sorbicillinoids exhibiting cytotoxic, antimicrobial, anti-inflammatory, phytotoxic, and α-glucosidase inhibitory activities. In recent years, marine-derived, extremophilic, plant endophytic, and phytopathogenic fungi have emerged as important resources for diverse sorbicillinoids with unique skeletons. The recently revealed biological activities of sorbicillinoids discovered before 2016 are also described in this review.

Five new chlamydosporol derivatives, named pleospyrones A-E (1–5), together with one known congener (6), were isolated from the culture of the endophytic fungus Pleosporales sp. Sigrf05, obtained from the medicinal plant Siraitia grosvenorii. The structures of the new compounds were elucidated mainly by analysis of the HRESIMS, and (1D, 2D) NMR data, while ECD and optical rotation calculations were used to assign the absolute configurations. The plausible biosynthetic pathway of these compounds were proposed. The isolated compounds were evaluated for their cytotoxicity, antifungal and antibacterial activities. Compounds 1, and 4–6 were cytotoxic against the tested cancer cells with IC50 values of 1.26~47.5 μM. Compounds 1–3 showed moderate antifungal activities against Magnaporthe oryzae, while compound 5 displayed weak antibacterial activity.

Four new 3,4-dihydroisocoumarin congeners, named lophiostomin A–D (1–4), together with two known α-pyridones (5 and 6) were isolated from cultures of the endophytic fungus Lophiostoma sp. Sigrf10 obtained from Siraitia grosvenorii.