## 1 Introduction  
The incidence of obesity has doubled during the last three decades and it has become a public health problem worldwide. The increasing prevalence of obesity can lead to an increasing prevalence of type 2 diabetes as well. Diabetes affects more than 400 billion patients worldwide [1]. Most anti-obesity medications are pharmacological agents with undesirable side effects [2]. Applied strategies to reduce the glycemic index (GI), like increasing resistant starch or dietary fiber and reducing the proportion of refined carbohydrates, may also cause side effects, such as stomach flatulence [3]. Therefore, the development of plant-derived nutraceuticalals and dietary supplements or bioactive food ingredients has become very important. These ingredients, besides polyphenols and dietary fibers, also include bioactive proteins, and these proteins have an important role in controlling human metabolism. More research is required to identify bioactive peptides from plant sources against metabolic disorders. Recently, more attention has been given to legume-related research, as legumes accumulate large amounts of proteins during their development, and these proteins are termed as storage proteins and non-storage bioactive proteins. The non-storage bioactive proteins can be enzymes, enzyme inhibitors, hormones, transporter proteins, structural proteins, or allergens [4]. Natural alpha-amylase inhibitors (\(\alpha\)AIs) are considered as promising new drugs in the treatment of metabolic diseases [5]. \(\alpha\)AIs impede the activity of the alpha-amylase enzyme during digestion by blocking access to the active site of the enzyme. This inhibition in the starch breakdown process leads to the lowering of the glucose levels of the blood. This action of \(\alpha\)AI-1 has been considered for potential application in the therapy of obesity and diabetes. Two isoforms of \(\alpha\)AIs and an \(\alpha\)AI-like protein have been reported in common beans. Only the \(\alpha\)AI-1 form inhibits the \(\alpha\)-amylase enzymes of mammals and insects, the \(\alpha\)AI-2 inhibits the \(\alpha\)-amylase enzymes of several insects, and the \(\alpha\)AI-like protein (also known as \(\alpha\)AI-3) is completely inactive towards amylase enzymes and it represents an evolutionary intermediate between phytohemagglutinin (PHA), arcelin, and \(\alpha\)AI [6]. Enzymatically inactive \(\alpha\)AI-1 polypeptides are present in the embryonic axes and cotyledons of common beans (_Phaseolus vulgaris_). They are synthesized as a precursor--around 35 kDa--on the endoplasmic reticulum, modified in the Golgi apparatus, and, finally, transported to the protein storage vacuoles. The molecular weights of the proteolytically cleaved and active \(\alpha\)AI-1 polypeptides are 15-18 kDa [7]. Our earlier mass spectrometric data showed that the processed forms of \(\alpha\)AI-1s have high variability in their \(\alpha\)- and \(\beta\)-chain peptides in Hungarian common bean cultivars, and antibodies against Tendergreen bean \(\alpha\)AI-1 developed in rabbit recognized all the investigated forms [8]. In the 1980s, crude preparations of bean \(\alpha\)AI-containing products were marketed in the United States, but clinical studies showed that these products had no inhibitory activity. Later, a research group at Mayo Clinic developed a common white bean protein extract containing \(\alpha\)AI and tested it in clinical experiments as a possible alternative for obesity treatment and glycemic control. This partially purified bean product was found to cause body weight loss and reduce spikes in blood sugar due to its \(\alpha\)AI activity [9]. Later, studies confirmed the preliminary hypothesis and results. They found that the bean \(\alpha\)AI reduces the absorption of complex carbohydrates and lowers blood glucose concentration, C-peptide, and gastric inhibitory polypeptide (GIP) levels [10]. [PERSON] et al.