Up to now, more than 250 phytosterols have been identified, with β-sitosterol, stigmasterol, and campesterol being the most commonly found in the diet.
It possesses proven antidiabetic activity. Phytosterols can act as ligands for PPARs (Peroxisome proliferator-activated receptor), reduce visceral fat accumulation, and reduce the concentration of glycosylated hemoglobin, serum glucose, nitric oxide, and substances that react with thiobarbituric acid, and they can increase serum insulin and pancreatic antioxidants.
The importance of phytosterols is due to their action of reducing low-density lipoprotein (LDL) cholesterol levels, and a daily consumption of 2–3 g of phytosterols could decrease the LDL-cholesterol by 10–15%.
Banana fruit has been shown to contain a good amount of phytosterols both in the peel and pulp. The phytosterols content in unripe banana in the range of 2.8 to 12.4 g·kg DW has been reported.
Phytosterols isolated from banana flowers (e.g., β-sitosterol and 31-norcyclolaudenone) inhibit amylase as an uncompetitive inhibitor, with a km value of 5.51 μg/mL. Phytosterols also can be found in fruits, vegetables, beans, nuts, legumes, whole grains, tubers, wheat germ, vegetable oils, and sunflower seeds.
Phytosterols cannot be synthesized endogenously in humans and are derived solely from diet. The biosynthesis of these compounds occurs through the succession of 30 enzyme-catalyzed reactions.
Phytosterols
