Pannorin B, a New Naphthopyrone from an Endophytic Fungal Isolate of Penicillium Sp.

The herbal remedy, milk thistle (Silybum marianum), has been used in traditional medicine for various liver, kidney, and gall bladder ailments. For over a decade, our research group has been investigating the flavonolignans obtained from this medicinal herb for cancer chemoprevention and hepatoprotection.1-6 Recently, we extended our studies toward examining the diversity as well as distribution patterns of fungal endophytes in leaves, stem, and roots of milk thistle.7 These fungi inhabit the internal living tissues of the host plants asymptomatically, though they may also cause disease over time.8 In addition to the phylogenetic profiling of these endophytes, a series of fungal extracts were also examined for chemical composition. Although the plant–endophyte relationship may or may not be mutualistic, the compounds produced by some endophytes could play a role in the growth and survival of the host. In a previous study, Penicillium restrictum, isolated from milk thistle, yielded promising secondary metabolites.9 Hence, in pursuit of interesting chemistry, a related monoverticillate endophytic Penicillium sp. was explored