106
7
. Fig. 7.6 Cauliflorous pods and opened fruit of a cacao plant (© Ute C. Vothknecht)
It should also be noted that caffeine is metabolized in the body to other compounds
such as theobromine, theophylline and paraxanthine (Fredholm et al. 1999). All of these
are not only metabolization products of caffeine but also found in various plants.
Theobromine is the major active ingredient in cacao (Theobroma cacao, . Fig. 7.6). It has
similar properties as caffeine but is much less potent.
Caffeine released from decaying seeds and leaves accumulates in the soil where it
causes allelopathic effects. It was suggested that this is due to the inhibitory effect of caffeine on mitosis as observed in lettuce (Friedman and Waller 1983) and is one of the
growth-limiting problems in intercropped coffee plantations (Bustos et al. 2008). While
this effect is important for growers who want to diversify by intercropping coffee with
medicinal and aromatic plants, it is unclear whether it plays a role in warding off competition by other plants under natural conditions. In a similar way, the exuding of caffeine
from primary roots was suggested to cause an allelopathic effect but more likely is a way
to fend off underground attacks by nematodes (Baumann 2006). Caffeine also might have
a use in attracting pollinators since it was shown that it can enhance the reward memory
of bees (Wright et al. 2013).
In addition to caffeine and related alkaloids, also some flavones act on the adenosine
receptor (Jacobson et al. 2002). These include galangin found in some plants from the ginger family or the Helichrysum genus as well as cirsimarin and cirsimaritin, flavonoids from
the traditional medicinal plant Microtea debilis (Hasrat et al. 1997). Also, aurones such as
hispidol that are widely distributed in yellow flowering plants and have a role in flower
colouring and stress response (Pare et al. 1991) have been identified as adenosine receptor
antagonists (Jacobson et al. 2002).
Chapter 7 · Plant-Derived Drugs Affecting GPRCs
7
. Fig. 7.6 Cauliflorous pods and opened fruit of a cacao plant (© Ute C. Vothknecht)
It should also be noted that caffeine is metabolized in the body to other compounds
such as theobromine, theophylline and paraxanthine (Fredholm et al. 1999). All of these
are not only metabolization products of caffeine but also found in various plants.
Theobromine is the major active ingredient in cacao (Theobroma cacao, . Fig. 7.6). It has
similar properties as caffeine but is much less potent.
Caffeine released from decaying seeds and leaves accumulates in the soil where it
causes allelopathic effects. It was suggested that this is due to the inhibitory effect of caffeine on mitosis as observed in lettuce (Friedman and Waller 1983) and is one of the
growth-limiting problems in intercropped coffee plantations (Bustos et al. 2008). While
this effect is important for growers who want to diversify by intercropping coffee with
medicinal and aromatic plants, it is unclear whether it plays a role in warding off competition by other plants under natural conditions. In a similar way, the exuding of caffeine
from primary roots was suggested to cause an allelopathic effect but more likely is a way
to fend off underground attacks by nematodes (Baumann 2006). Caffeine also might have
a use in attracting pollinators since it was shown that it can enhance the reward memory
of bees (Wright et al. 2013).
In addition to caffeine and related alkaloids, also some flavones act on the adenosine
receptor (Jacobson et al. 2002). These include galangin found in some plants from the ginger family or the Helichrysum genus as well as cirsimarin and cirsimaritin, flavonoids from
the traditional medicinal plant Microtea debilis (Hasrat et al. 1997). Also, aurones such as
hispidol that are widely distributed in yellow flowering plants and have a role in flower
colouring and stress response (Pare et al. 1991) have been identified as adenosine receptor
antagonists (Jacobson et al. 2002).
Chapter 7 · Plant-Derived Drugs Affecting GPRCs