br Acknowledgements This work was financed by the

Acknowledgements This work was financed by the projects “Mejora Genética del Almendro” (MINECO-Spain, AGL2017-85042-R), “The molecular mechanisms to break flower bud dormancy in fruit trees” to RS-P within the Villum Young Investigator Program and by the VILLUM Research Center for Plant Plasticity-Denmark and “Breeding stone fruit species assisted by molecular tools” (Fundación Séneca-Spain).
Introduction α-Glucosidase (EC 3.2.1.20), a glucosidase located in the Psalmotoxin 1 mg of the small intestine that acts upon α(1→4) glycosidic bonds, is an important catabolic enzyme in the digestive process of carbohydrates in food [1,2]. Carbohydrates are normally converted into simple sugars (monosaccharides) that can be absorbed through the intestine. Classic α-glucosidase inhibitors are oral antidiabetic drugs that can be used for type 2 diabetes mellitus treatment through their prevention of carbohydrate (such as starches and table sugar) digestion [3]. Due to its critical roles in the key steps of the metabolic process of polysaccharides, particularly plasma blood regulation [4], characterization of α-glucosidase activity and its inhibition is of great interest. In recent decades, several types of α-glucosidase inhibitors, such as miglitol [5], voglibose [6], and acarbose [7], have been used widely as antidiabetic drugs. These chemicals act functionally by inhibiting α-glucosidase activity to prevent carbohydrate digestion from releasing digested single sugars. Additionally, α-glucosidase reportedly participates in the immune response associated with aspects of Pompe disease [8,9], glycoprotein trafficking [10,11], tumorigenesis [12], and cancer [[13], [14], [15]]. Therefore, a better understanding of the effects and mechanisms of biomolecule inhibitors on regulating α-glucosidase would be highly beneficial. Phloroglucinols are bioactive compounds mainly isolated from marine brown alga (especially the families Phaeophyceae and Fucaceae), plants, and microorganisms [16,17]. Phloroglucinol-containing herbs have been utilized as traditional medicine in China, Southern Africa, and Latin America. According to their molecular weight, phloroglucinol compounds are classified as monomeric, dimeric, trimeric, tetrameric, and phlorotannins [18]. In the recent decade, phloroglucinol (1,3,5-trihydroxybenzene) and its derivatives were shown to be bioactive and capable of performing various biological activities, such as those associated with antimicrobial, anti-allergic, anti-inflammatory, and antioxidant activities, as well as inhibiting human immunodeficiency virus-1 reverse transcriptase and protease activities [[19], [20], [21], [22], [23]]. Additionally, this biomolecule is also used to detect aldehydes, diazo-type copying, and textile dyes [18]. Recently, several studies of α-glucosidase inhibition were conducted using L-malic acid [24], stilbene derivatives [25], chromenone derivatives [26], syzygium derivatives [27], calcium [28], hydroxysafflor yellow A [29], cobalt [30], and hesperetin [31]. To expand the understanding of the effects and mechanisms associated with α-glucosidase inhibitors, we investigated the effects of phloroglucinol on α-glucosidase activity using serial enzyme-inhibition kinetics, protein-ligand docking, and computational molecular dynamics (MD) simulations. Based on its three-hydroxyl functional structure and binding capacity for the residues of target enzymes, we hypothesized that phloroglucinol could inhibit α-glucosidase due to its affinity for the active site pocket of the enzyme, details of which might aid in the development of other α-glucosidase inhibitors. Moreover, our pre-simulation prediction of phloroglucinol binding to α-glucosidase to inhibit its activity matched the results of computational simulations to assess the inhibition kinetics. Furthermore, we suggested that similar compounds (hydroxyl phenolic compounds) capable of targeting the key α-glucosidase residues could be potential inhibitory agents.