Hypericum androsaemum L. is an herbaceous plant widely distributed throughout Europe which has been used
in traditional medicine on account of the diuretic and hepatoprotective properties
of its leaves [1]. These biological effects have been ascribed to the different flavonoids
and phenolic acids known to be present in this species. Cell suspension cultures established
from hypocotyl-derived callus of H. androsaemum were reported [2] to accumulate low amounts of flavonoids, with the highest levels
being found during the stationary phase (day 14). More recently [3], it was shown
that treatment of 11-day-old cultures for 72h with 15 mM CaCl2 or 5µM calcium ionophore A23187 increased considerably the accumulation of flavonoids
and the activity of phenylalanine ammonia-lyase (PAL), which is the first committed
enzyme in the phenylpropanoid pathway. In similar experiments, the addition of 20µM
forskolin (an activator of adenylyl cyclase) or 100µM dibutyryl cAMP (db-cAMP, a membrane-permeable
analogue of cAMP) also enhanced the flavonoid levels recorded on day 14, but only
the latter treatment caused a significant increase in PAL activity. Moreover, the
stimulatory effects of db-cAMP were prevented or markedly inhibited by pretreatment
of cells with the calcium channel blocker verapamil (100µM). Taken together, these
results suggest that both calcium and cAMP are involved in flavonoid metabolism of
H. androsaemum cell cultures.
Acknowledgements: FCT and POCTI/FEDER for financial support
References: 1. Novais, M. et al. (2004)J. Ethnopharmacol. 93: 183–195.
2. Paranhos, A. (2006) Planta Med. 72: 1060–1061.
3. Paranhos, A. (2007) Planta Med. 73: 1017.
