Frullania is one of the largest and taxonomically most complex genus of leafy liverworts. Current morphology-based estimates of Frullania diversity are close to 400 species; however, species level-classification of Frullania has been regarded notoriously difficult and subject to many studies. The liverworts classified in this genus have been studied using morphological evidence and molecular markers but also in terms of secondary metabolite composition. Up to now 98 Frullania species have been chemically investigated. As a result, it is known that Frullania species are characterized by a remarkable chemical diversity. The most characteristic compounds present in this liverwort genus are sesquiterpene lactones with eudesamnolides as the most diverse group, and aromatic compounds belonging to bibenzyls. In this review paper we report the distribution of secondary metabolites in all chemically investigated Frullania species and discuss some aspects concerning the division of this genus into chemotypes.

A new sesquiterpenoid, chaenomelesterpenoid A (1), and a new norisoprenoid, chaenomelesterpenoid B (2), were isolated from the fruits of Chaenomeles sinensis (Thouin) Koehne. Their structures were determined by NMR spectroscopy and MS. In addition, the protective effects of the compounds were tested against corticosterone-induced damage in PC-12 cells using real-time cellular analysis (RTCA). Compounds 1 and 2 significantly improved cell viability and corticosterone-induced damage in PC-12 cells with EC₅₀ values of 15.7 and 12.6 µM, respectively.