Study of dynamic accumulation of secondary metabolites in three subspecies of Hypericum perforatum.

St. John's Wort extracts are used for the treatment of mild to moderately severe depression, and their composition and standardization have been thoroughly investigated. Standardization of St. John's Wort extracts has to cope with several factors that affect the phytochemical profile of the plant, with geographic location, seasonal variations and subspecies all being important. To address this issue, three different subspecies of Hypericum perforatum L. were profiled in relation to different maturation phases, evaluating the variations in the context of the major secondary metabolites from this plant. HPLC analysis indicated that H. perforatum subsp. perforatum is richer in secondary metabolites than the other subspecies, and that the three subspecies show a different profile during the developmental stages. Hypericins, hyperforins and flavonoids peak at quite different stages, and the standardization of Hyperici extracts based only on the contents of hypericin is not adequate to guarantee batch reproducibility of the extracts.

Hyperforin inhibits cancer invasion and metastasis.

Hyperforin (Hyp), the major lipophilic constituent of St. John's wort, was assayed as a stable dicyclohexylammonium salt (Hyp-DCHA) for cytotoxicity and inhibition of matrix proteinases, tumor invasion, and metastasis. Hyp-DCHA triggered apoptosis-associated cytotoxic effect in both murine (C-26, B16-LU8, and TRAMP-C1) and human (HT-1080 and SK-N-BE) tumor cells; its effect varied, with B16-LU8, HT-1080, and C-26 the most sensitive (IC50 = 5 to 8 micromol/L). At these concentrations, a marked and progressive decline of growth was observed in HT-1080 cells, whereas untransformed endothelial cells were only marginally affected. Hyp-DCHA inhibited in a dose-dependent and noncompetitive manner various proteinases instrumental to extracellular matrix degradation; the activity of leukocyte elastase was inhibited the most (IC50 = 3 micromol/L), followed by cathepsin G and urokinase-type plasminogen activator, whereas that of the matrix metalloproteinases (MMPs) 2 and 9 showed an IC50 > 100 micromol/L. Nevertheless, inhibition of extracellular signal-regulated kinase 1/2 constitutive activity and reduction of MMP-2 and MMP-9 secretion was triggered by 0.5 micromol/L Hyp-DCHA to various degrees in different cell lines, the most in C-26. Inhibition of C-26 and HT-1080 cell chemoinvasion (80 and 54%, respectively) through reconstituted basement membrane was observed at these doses. Finally, in mice that received i.v. injections of C-26 or B16-LU8 cells, daily i.p. administration of Hyp-DCHA-without reaching tumor-cytotoxic blood levels-remarkably reduced inflammatory infiltration, neovascularization, lung weight (-48%), and size of experimental metastases with C-26 (-38%) and number of lung metastases with B16-LU8 (-22%), with preservation of apparently healthy and active behavior. These observations qualify Hyp-DCHA as an interesting lead compound to prevent and contrast cancer spread and metastatic growth.

Detection of hypericins in the "red glands" of Hypericum elodes by ESI-MS/MS.

The biologically active naphthodianthrones hypericin and pseudohypericin were detected by electrospray ionization mass spectrometry (ESI-MS/MS) in microsamples from the sepals of Hypericum elodes (Hypericaceae) containing the so-called "red glands", i.e. stipitate glands with red-coloured heads. The occurrence of hypericins in the red glands of H. elodes supports the taxonomic position of the section Elodes within the genus Hypericum and provides evidence that the ability of carrying out the biosynthetic pathway leading to the naphthodianthrone compounds, rather than the absolute amounts produced, should be regarded as a chemical marker of the phylogenetically more advanced sections of genus Hypericum. The biologically active phloroglucinol derivatives hyperforin and adhyperforin, so far found only in H. perforatum, were also detected and evidence for their localization in the sepal secretory canals with large lumen, is given.

Melatonin in plants.

A widespread occurrence of melatonin in plant kingdom has been reported. The circadian rhythm in the level of melatonin observed in both unicellular algae and higher plants, suggests a role in regulation of photoperiodic and rhythmic phenomena, i.e. a similar function for melatonin in both plants and animals. Evidence has been obtained for a role of melatonin in plant morphogenesis, but more research is needed to ascertain other suggested physiological roles in higher plants (seed dormancy regulation, radical scavenger activity, interaction with calmodulin) as well the ecological significance of the high melatonin levels recorded in alpine plants. Setting-up more reliable analytical methods for melatonin detection and quantification is a basic requirement to get more insight into melatonin roles in plant physiology and ecology.