Maltoheptaose

A key strategy to mitigate postprandial hyperglycemia involves inhibiting α-amylases, which commence the starch digestion process in the gut. This study examined the inhibitory effects of resveratrol and stilbenoid tetramers, vaticanol B, (−)-hopeaphenol, and vatalbinoside A on human salivary and pancreatic α-amylases experimentally and through molecular docking studies. Vaticanol B demonstrated the most potent inhibition with IC₅₀ values of 5.3 ± 0.3 μM for salivary and 6.1 ± 0.5 μM for pancreatic α-amylase (compared to acarbose with IC₅₀ values of 1.2 ± 0.1 μM and 0.5 ± 0.0 μM, respectively). Kinetic analysis suggested a competitive inhibition mode for vaticanol B. Resveratrol and vatalbinoside A were poor inhibitors of human α-amylases, while (−)-hopeaphenol exhibited moderate inhibition. Molecular docking supported the inhibition data, and several aspects of the structural configurations explained the stronger inhibition exerted by vaticanol B. Overall, vaticanol B shows promise as a natural alternative to acarbose for inhibiting α-amylase.

(Poly)phenols inhibit α-amylase by directly binding to the enzyme and/or by forming starch-polyphenol complexes. Conventional methods using starch as the substrate measure inhibition from both mechanisms, whereas the use of shorter oligosaccharides as substrates exclusively measures the direct interaction of (poly)phenols with the enzyme. In this study, using a chromatography-based method and a short oligosaccharide as the substrate, we investigated the detailed structural prerequisites for the direct inhibition of human salivary and pancreatic α-amylases by over 50 (poly)phenols from the (poly)phenol groups: flavonols, flavones, flavanones, flavan-3-ols, polymethoxyflavones, isoflavones, anthocyanidins and phenolic acids. Despite being structurally very similar (97% sequence homology), human salivary and pancreatic α-amylases were inhibited to different extents by the tested (poly)phenols. The most potent human salivary α-amylase inhibitors were luteolin and pelargonidin, while the methoxylated anthocyanidins, peonidin and petunidin, significantly blocked pancreatic enzyme activity. B-ring methoxylation of anthocyanidins increased inhibition against both human α-amylases while hydroxyl groups at C3 and B3′ acted antagonistically in human salivary inhibition. C4 carbonyl reduction, or the positive charge on the flavonoid structure, was the key structural feature for human pancreatic inhibition. B-ring glycosylation did not affect salivary enzyme inhibition, but increased pancreatic enzyme inhibition when compared to its corresponding aglycone. Overall, our findings indicate that the efficacy of interaction with human α-amylase is mainly influenced by the type and placement of functional groups rather than the number of hydroxyl groups and molecular weight.

The pseudotetrasaccharide acarbose, produced by Actinoplanes sp. SE50/110, is a relevant secondary metabolite used in diabetes type II medication. Although maltose plays a crucial role in acarbose biosynthesis, the understanding of the maltose/maltodextrin metabolism and its involvement in acarbose production is at an early stage. Here, we reconstructed the predicted maltose–maltodextrin pathway that involves four enzymes AmlE, MalZ, MalP, and MalQ. An investigation of enzyme activities was conducted through in vitro assays, leading to an expansion of previously postulated substrate spectra. The maltose-induced α-glucosidase AmlE is noteworthy for its high hydrolysis rate of linear α-1,4-glucans, and its capability to hydrolyze various glycosidic bonds. The predicted maltodextrin glucosidase MalZ showed slow hydrolysis activity on linear α-glucans, but it was resistant to acarbose and capable of releasing glucose from acarbose. AmlE compensates for the low activity of MalZ to ensure glucose supply. We determined the enzyme activity of MalP and its dual function as maltodextrin and glycogen phosphorylase. The 4-α-glucanotransferase MalQ plays a central role in the maltose/maltodextrin metabolism, alongside MalP. This study confirmed the simultaneous degradation and synthesis of long-chain α-glucans. The product distribution showed that with an increasing number of glycosidic bonds, less glucose is formed. We found that MalQ, like its sequence homolog AcbQ from the acarbose biosynthetic gene cluster, is involved in the formation of elongated acarviosyl metabolites. However, MalQ does not participate in the elongation of acarbose 7-phosphate, which is likely the more readily available acceptor molecule in vivo. Accordingly, MalQ is not involved in the formation of acarviosyl impurities in Actinoplanes sp. SE50/110.

The pseudo-tetrasaccharide acarbose, produced by Actinoplanes sp. SE50/110, is a α-glucosidase inhibitor used for treatment of type 2 diabetes patients. In industrial production of acarbose, by-products play a relevant role that complicates the purification of the product and reduce yields. Here, we report that the acarbose 4-α-glucanotransferase AcbQ modifies acarbose and the phosphorylated version acarbose 7-phosphate. Elongated acarviosyl metabolites (α-acarviosyl-(1,4)-maltooligosaccharides) with one to four additional glucose molecules were identified performing in vitro assays with acarbose or acarbose 7-phosphate and short α-1,4-glucans (maltose, maltotriose and maltotetraose). High functional similarities to the 4-α-glucanotransferase MalQ, which is essential in the maltodextrin pathway, are revealed. However, maltotriose is a preferred donor and acarbose and acarbose 7-phosphate, respectively, serve as specific acceptors for AcbQ. This study displays the specific intracellular assembly of longer acarviosyl metabolites catalyzed by AcbQ, indicating that AcbQ is directly involved in the formation of acarbose by-products of Actinoplanes sp. SE50/110.

Four different soluble fibres were evaluated as sugar replacers in short dough biscuits: two resistant dextrins (Nutriose® FM06 and Promitor® SGF 70R) and two inulin-derived fibres (Orafti® HSI and Fibruline™ Instant). The degree of polymerisation of the fibres was analysed, and dough viscoelastic properties were assessed. Weight loss during baking, dimensions, textural properties, surface colour and sensory profile were evaluated. Higher degree of polymerisation fibres (e.g. Fibruline) limited water availability for syrup formation, restricting dough expansion and resulting in smaller, more compact, and harder biscuits than control. Biscuits with inulin derived fibres with a lower degree of polymerisation (e.g. Orafti) showed similar dimensions to control biscuits. In general, sucrose reduction gave place to biscuits with lower resistance to penetration and fracture strength due to less sugar recrystallisation in the final biscuit. In contrast, when dextrin-type fibres were used the rheological behaviour of the dough, spreading during baking, and resistance to penetration were similar to the control as the fibres showed an anti-plasticising effect similar to sucrose. However, all reduced sugar biscuits were significantly firmer and crunchier in sensory profile suggesting further optimisation is needed, potentially by modification of the fibre structure or baking method.

Surplus bread is a major bakery side stream that should be strictly kept within the human food chain to reduce waste and ensure resource efficiency in baking processes. Optimally, surplus bread should be recycled as a dough ingredient, however, this is known to be detrimental to the volume and texture of bread. The purpose of this study was to investigate how gelatinized starch in surplus bread, untreated or enzymatically hydrolyzed, affects dough development, bread volume and textural attributes. Starch was hydrolyzed to various degrees using commercial α-amylase and amyloglucosidase. Bread hydrolysates containing different carbohydrate profiles (untreated, 75%, 57%, and 26% starch remaining) were evaluated as dough ingredients. More complete starch hydrolysis resulted in better dough visco-elastic properties and higher dough level, and reduced dough water absorption by 13%. Nonetheless, breads containing hydrolysate with high-malto-oligosaccharides had the lowest intrinsic hardness and similar volume yield when compared to control bread. Furthermore, compared to untreated slurry, the hydrolysate with high-malto-oligosaccharides, reduced crumb hardness by 28% and staling rate by 42%, and increased specific volume by 8%. The present findings show that enzymatic hydrolysis dramatically transforms the impact of gelatinized starch. Thus, by selecting correct bioprocessing approaches, bread recycling performance may be significantly improved.