Polypeptide-p
Bitter melon is one of the most commonly used vegetable that contains polypeptide-p and is used to control diabetes naturally[41]. Polypeptide-p or p-insulin is an insulin-like hypoglycemic protein, shown to lower blood glucose levels in gerbils, langurs and humans when injected subcutaneously[42]. The p-insulin works by mimicking the action of human insulin in the body and thus may be used as plant-based insulin replacement in patients with type-1 diabetes[43]. Recently, Wang et al. have cloned and expressed the 498 bp gene sequence coding for the M. charantia polypeptide p gene and have also proved the hypoglycemic effect of the recombinant polypeptide in alloxan induced diabetic mice[44]. The oral intake of the extract from bitter melon seeds does produce hypoglycemic effects in streptozotocin (STZ) induced type-1 diabetic rats[32]. This indicates that compounds in bitter melon seeds other than p-insulin may also be effective in the treatment of type-1 diabetes.