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Pallambins A (1) and B (2), two novel 19-nor-7,8-secolabdane diterpenoids with unprecedented tetracyclo[4.4.0(3,5).0(2,8)]decane skeletons, along with a pair of structurally related isomers, pallambins C (3) and D (4), were isolated from the Chinese liverwort Pallavicinia ambigua. Their structures with absolute configurations were determined by means of NMR, X-ray diffraction, and CD analyses. Their preliminary cytotoxicity to human cancer cells was also tested.

Isoriccardin C (1) and riccardin D (2), isolated from the liverwort Reboulia hemisphaerica, were first characterized to be a mixture of two enantiomeric atropisomers by online chiral high-performance liquid chromatography-circular dichroism (HPLC-CD) analysis. Exemplarily for bisbibenzyls of the diarylether-biphenyl type, the absolute atropisomeric configurations of compunds 1 and 2 were determined by the analysis of their CD data coupled with quantum chemical CD calculations.

Six macrocyclic bis(bibenzyls) were obtained from the Chinese liverwort Ptagiochasm intermedlum L., and their structures were elucidated as pakyonol (1), neomarchantin A (2), isoriccardin C (3), marchantin H (4), riccardin F (5) and riccardin C (6) on the basis of spectroscopic data and comparison with known compounds. Among them, compounds 3-5 were isolated from this liverwort species for the first time. They possessed in vitro antifungal properties against the fluconazole-sensitive and resistant strains of Candida albicans, with minimum inhibitory concentrations (MICs) ranging from 32 to >512 microg mL(-1). Furthermore, riccardin C was also demonstrated to act as a fungal resistance modifying agent when its combined effect with fluconazole on three resistant strains of C. albicans was investigated. The synergistic or additive activity of riccardin C caused dramatically reduced MICs of fluconazole by at most 256-fold.

Three new rearranged ent-kaurane-type diterpenoids (1-3) and seven new ent-kaurane-type diterpenoids (4-10) have been isolated from the liverwort Jungermannia atrobrunnea. Their structures were determined by extensive spectroscopic techniques and X-ray crystallographic analysis. The absolute configurations of these compounds were clarified by CD spectroscopic studies. Compound 1 is the first example of a rearranged ent-kaurane diterpenoid possessing a peroxide bridge.