Understanding the biological activity of Hypericum species through metabolomics studies
George A. Kraus
The Hypericum genus contains plants which biosynthesize various polyketides with various known and unknown biological and medicinal activities. However, many Hypericum species have not been chemically or biochemically characterized. These species represent an opportunity for understanding chemical ecology and for new drug discovery research. Acyl-phloroglucinols are of particular interest since they are the most diverse class of specialized metabolites in Hypericum. We used analytical methods such as HPLC, LC-MS and 2-D NMR to screen Hypericum species for metabolite diversity. One species, H. gentianoides, was investigated further based on its historical use by Native Americans and its unique metabolite fingerprint. This species was found to contain a set of biochemically-related dimeric acyl-phloroglucinols. Furthermore, H. gentianoides extracts revealed these compounds induce various biological responses in mammalian cells including anti-inflammatory responses, TRPV1 pain receptor-dependent calcium influx, and inhibition of two lentiviruses (HIV and EIAV). Extracts were highly cytotoxic to HeLa cancer cells. Bioactivity-guided fractionation of extracts defines specific acyl-phloroglucinols associated with the bioactivities. We propose that the bioactivities of these biochemically related acyl-phloroglucinols represent a coordinated process that alters cellular processes in other organisms via redox changes and protein interactions.