Lichenized fungi, recognized as an ecologically vital and pharmaceutically promising resource, hold substantial value in both environmental conservation and medicinal applications. As the second largest subclass within the lichen-forming fungi of Lecanoromycetes, Ostropomycetidae emerged as a critical reservoir of bioactive secondary metabolites. Current research has revealed that these secondary metabolites demonstrate remarkable bioactivities, positioning them as potential sources for novel pharmaceutical compounds. Despite considerable progress in characterizing chemical constituents and evaluating bioactivities within this subclass, a systematic summary of these discoveries remains absent. This review synthesizes the lichenochemical research progress, providing critical evaluations of 202 structurally characterized compounds from Ostropomycetidae lichen species over recent decades. These Ostropomycetidae-derived compounds cover the phenols, polyketides, fatty acids, terpenoids, steroids, and non-ribosomal peptides, and exhibit diverse bioactivities including antitumor, anti-inflammatory, antibacterial, antifungal, antiviral, antioxidant, anti-angiogenic, anti-neurodegenerative diseases, antitubercular, anti-herbivore, and antitrypanosomal, and so on. The aim of this review is to establish a robust chemodiversity framework and to offer strategic guidance for targeted exploration of lichen-derived drug candidates in the biological resources of Ostropomycetidae lichens.

Four new species of the lichen genus Diorygma from China are described based on morphological, chemical, and phylogenetic evidence. Phylogenetic analyses were conducted using both RAxML and Bayesian posterior probability inference, based on combined LSU and mtSSU sequences. The characteristic compounds were analyzed by colorimetric reactions and thin-layer chromatography. Diorygma guizhouense is characterized by small apothecia, a narrow to slightly open disc covered with white pruina, and the presence of stictic, salazinic, and norstictic acids. Diorygma leigongshanense is characterized by small, oval apothecia, a disc surrounded by entire, raised, and widely open thalline margins covered with thin, pale yellowish pruina, and the same chemical substances as D. guizhouense. Diorygma locitonitrus is distinguished by the presence of salazinic acid and hyaline, richly muriform ascospores, notably with distinctly smaller peripheral cells compared to the central cells. Diorygma weii is characterized by stellately branched apothecia with a closed to slit-like disc, a milky white thallus tinged with green, and the presence of only norstictic acid. Detailed morphological descriptions and illustrations of the new species are provided, along with a comprehensive species checklist highlighting the diagnostic characteristics of the known species in this genus.

Based on morphological, chemical and molecular studies, two new species of the lichen genus Letrouitia are newly described from China. Letrouitia arcuata is distinguished by its arcuate ascospores [8–10(–12)-locular, (28–)33–50(–62.5) × (8–)10–14.5 µm] and L. sinuosa by its ascomata with wavy margins and ascospores with lens-shaped locules [6–8-locular, (18–)19.5–32(–34) × (6.5–)8–14 μm]. In addition, L. magenta is reported for the first time as a new record in China, characterized by small and round ascomata. The descriptions, distribution and phylogenetic analysis of the respective species have been actualized and a key to the Letrouitia species known from China is provided.

During our research on the lichen genus Carbacanthographis from China, two species new to science were discovered in materials from Yunnan and Guangxi Provinces, i.e. Carbacanthographis crassibasalia sp. nov. with a corticate thallus, a completely carbonized excipulum, warty periphysoid tips, hyaline, muriform, 6–18 × 3–4-septate ascospores, and protocetraric acid and C. yunnanensis sp. nov. with an ecorticate thallus, a completely carbonized excipulum, warty periphysoid tips, hyaline, small, submuriform 4–6 × 0–1-septate ascospores and the presence of protocetraric acid. A new record for China, C. iriomotensis, collected in Hainan Province is also reported. Detailed morphological descriptions as well as high-resolution photographs of the morphology and anatomy of the three species are provided. A working key to all the known Carbacanthographis species from China is also provided.

A new species of the lichenized fungi genus Diorygma is described from China: Diorygma jingningense Shu H. Jiang & Z.F. Jia, collected from Zhejiang Province. It is characterized by a saxicolous and pseudocorticate thallus, erumpent lirellae with complete thalline margin, entire labia, uncarbonized excipulum, hyaline hymenium, small, submuriform, 3 × 0–1-septate ascospores and the presence of norstictic and connorstictic acids. The placement of this new species was confirmed by a molecular phylogenetic approach based on combined mtSSU and nuLSU sequences, and is compared in detail with other similar species in the genus.

Based on morphological, chemical and molecular data, a new species, Platygramme guizhouensis is described to science, and Phaeographis decipiens is reported as new record to China. Platygramme guizhouensis features lirelliform apothecia with discs open, black, epruinose, proper exciple apically carbonized, wedge-shaped. Asci cylindrical to clavate, 8-spored. Ascospores brown, elongate-ellipsoid, 9–12 transverse septa, I+ violet-purple. Detailed descriptions and illustrations of the new species and the new record are provided.