Hunting for bis-bibenzyls in Primula veris subsp. macrocalyx (Bunge) Lüdi: Organ-specific accumulation and cytotoxic activity

Abstract Twenty-one accessions of Primula veris subsp. macrocalyx (Primulaceae) were chemically analyzed to clarify the presence of naturally rare macrocyclic bis-bibenzyls (BB). These compounds are typically found in liverworts but not known from higher plants, with the exception of the species under study. However, data are scarce concerning organ specific accumulation of BB in populations of the Primula. Comparative HPLC profiling of methanolic extracts of different parts of the plants revealed that these compounds are predominantly accumulated in the rhizome parts of the plant, in varying and sometimes quite small amounts. This is suggestive for a possible role as dihydrostilbenoid phytoalexins. Riccardin C was isolated as the main BB derivative, and its structure was elucidated on basis of NMR and mass spectral data, which is in alignment with earlier publications. In addition, cytotoxic bioassays of structurally related BB riccardin C, perrottetin F, perrottetin E, and marchantin A, were carried out against three human cancer cell lines, the non-small cell lung carcinoma – A549, the colon carcinoma – SW480, and the ovarian teratocarcinoma −CH1/PA‐1, respectively. Riccardin C and perrottetin E showed a pronounced activity in concentrations between 23–36 μM with low dependence on intrinsic resistance of the cell lines. These tests might be a useful basis for future research. The possible ecological role of BB accumulation in the rhizomes of Primula is briefly addressed.