Diabetes mellitus (DM) is primarily caused by multiple defects in insulin metabolism such as insulin secretion, insulin action, or function. This metabolic disorder is also characterized by multiple defects, e.g., chronic hyperglycaemia and inefficient metabolism of carbohydrates, fats, and proteins. All these metabolic defects are directly or indirectly caused by inefficient or no activity of insulin produced by pancreatic cells. Diabetes mellitus is also known as the silent killer. It has long-lasting effects on many body organs, including their damage, dysfunction, and failure. In traditional approaches, many plant species have been used for the control and treatment of diabetes mellitus. There is a long list of molecules isolated from plants which are responsible for the reduction in plasma glucose level and therefore capable for use as hypoglycaemic drugs. Currently, there are many molecules isolated from plants emphasized by health care professionals to use for the control of blood glucose level, which have already been used for a long time in traditional therapeutic approaches for the treatment of DM in folk medicine. Although secondary metabolites have been appreciated for encouraging the action of plant extracts which act as hypoglycaemic agents, in the past years, less focus has been paid towards research which has shown the relation of hypoglycaemic activities of plant isolates to insulin-like plant proteins and their potential use for the control and treatment of DM. Many plant metabolites have been reported with very low side effects and therefore, can potentially be used as hypoglycaemic agents within affordable expenses. Natural hypoglycaemic agents also have a more effective hypoglycaemic approach towards DM when compared to synthetic drugs.

It is of increasing importance to produce oral hypoglycaemic drugs which are safer or have minimum side effects and are economically affordable. This high and serious demand is provoking researchers and health care professionals to produce hypoglycaemic oral drugs from natural sources like plants. Drugs isolated from plants are herbal drugs which are effective, safer, have minimum side effects and are budget friendly. Therefore, deep scrutinization of such agents from herbal resources is catching increasing attention in discovering new herbal drugs. Many hypoglycaemic peptides have been reported from different medicinal plants, and all of these peptides have been checked on animal models for their hypoglycaemic activities. When orally administrated, all have proved as an effective approach against DM. Some hypoglycaemic peptides are difficult to extract and purify because of their small size and low concentration in natural resources.

The aim of this Special Issue is to collate original research articles with a focus on hypoglycaemic proteins and peptides extracted from plants that are used to treat diabetes mellitus. Review articles discussing the current state of the art are also welcomed.

Potential topics include but are not limited to the following:

• Isolation of hypoglycaemic proteins and peptides
• Cloning and expression studies of hypoglycaemic proteins and peptides
• Purification and physicochemical properties of hypoglycaemic proteins and peptides
• In-silico characterisation of hypoglycaemic proteins and peptides
• In-vivo characterisation of hypoglycaemic proteins and peptides
• Gene/protein structures of hypoglycaemic proteins and peptides
• Orally active hypoglycaemic proteins and peptides from plant sources
• Mechanisms of action of hypoglycaemic proteins and peptides
• ADMET profiling of hypoglycaemic proteins and peptides