Pepper
Before concluding this section, we would like to mention also black pepper (Piper nigrum, Family Piperaceae), among the most widespread and most used spice in the world, although it has not yet been shown that it possesses significant anti-diabetic effects, except an anti-glycant activity in vitro [44]. However, pepper has, in addition to a high antioxidant activity, other properties that might enhance the anti-diabetic and antioxidant properties of the other spices. The antioxidant activity of pepper is mainly due to piper¬ine, the alkaloid contributing to the pungency of this spice. Black pepper or piperine treatment has been demonstrated to inhibit or quench free radicals and reactive oxygen species, and to positively influence cellular thiol status, antioxidant molecules and anti¬oxidant enzymes in vitro, and reduce lipid peroxida¬tion in vivo [60]. In addition, piperine strongly inhibits hepatic and intestinal aryl hydrocarbon hydroxy¬lase and UDP-glucuronyl transferase, two enzymes involved in both the bio-transforming reactions of drugs and phytochemicals, including phenolic sub¬stances, and the modulation of the bioavailability of these compounds. In addition, piperine enhances the bioavailability of a number of therapeutic drugs and phytochemicals, also through an interaction with the ultra-structure of intestinal brush border that causes an increase in intestinal absorption of these substances [60]. The effect of piperine on the bioavailability of phytochemicals deserves to be investigated more thoroughly, in order to clarify potential synergistic effects on the anti-diabetic and antioxidant activities of other spices.