Capsaicin CAS:404-86-4

Capsaicin is present in large quantities in the placental tissue (which holds the seeds), the internal membranes and, to a lesser extent, the other fleshy parts of the fruits of plants in the genus Capsicum. The seeds themselves do not produce any capsaicin, although the highest concentration of capsaicin can be found in the white pith of the inner wall, where the seeds are attached.

The seeds of Capsicum plants are dispersed predominantly by birds: in birds, the TRPV1 channel does not respond to capsaicin or related chemicals (avian vs. mammalian TRPV1 show functional diversity and selective sensitivity). This is advantageous to the plant, as chili pepper seeds consumed by birds pass through the digestive tract and can germinate later, whereas mammals have molar teethwhich destroy such seeds and prevent them from germinating. Thus, natural selection may have led to increasing capsaicin production because it makes the plant less likely to be eaten by animals that do not help it disperse. There is also evidence that capsaicin may have evolved as an anti-fungal agent:the fungal pathogen Fusarium, which is known to infect wild chilies and thereby reduce seed viability, is deterred by capsaicin, which thus limits this form of predispersal seed mortality.

In ***6, it was discovered that the venom of a certain tarantula species activates the same pathway of pain as is activated by capsaicin; this was the first demonstrated case of such a shared pathway in both plant and animal anti-mammal defense.