Hypermoins A-D: Rearranged Nor-Polyprenylated Acylphloroglucinols from the Flowers of Hypericum monogynum.

Hypermonins A-D (1-4), four rearranged nor-polycyclic polyprenylated acylphloroglucinols (PPAPs) with unprecedented skeletons, together with two new biosynthesis related PPAPs (5 and 6) were isolated and identified from the flowers of Hypericum monogynum. Hypermoins A-D represented the first examples of highly modified norPPAPs characterized by a rare 7/6/6/5-tetracyclic system. From the biogenic synthesis pathway analysis, all isolates shared the same biosynthetic intermediate, and the addition of two methyls or one methyl to this intermediate through methyltranferase could generate different types of PPAPs (1-7). Their planner structures as well as absolute configuration were confirmed via spectroscopic analysis, ECD calculation, and X-ray crystallography. All isolates potentially reversed multidrug resistance (MDR) activity in both two cancer cells, HepG2/ADR and MCF-7/ADR. Specifically, hypermoin E (5) and hyperielliptone HA (7) were found to be the best MDR modulators with the reversal fold ranging from 41 to 236, which is higher than the positive control verapamil.