In Vitro and In Vivo α-Glucosidase and α-Amylase Inhibitory Effects of the Water Extract of Leaves of Pepper (Capcicum Annuum L. Cultivar Dangjo ) and the Active Constituent Luteolin 7-O-Glucoside

Phytochemicals from Phillyrea latifolia L. leaves and fruit extracted with various solvents: Their identification and quantification by LC-MS and antihyperglycemic effects

Phillyrea latifolia L. is a type of shrubland, which is widely known as mock privet, and belongs to the Oleaceae family. The objective of this study was to compare and assess the phytochemical composition, antioxidant and antidiabetic activities of ethyl acetate, methanol and aqueous extracts of the fruit and leaves of P. latifolia L. Phenolics were analysed by detecting individual bioactive compounds using an LCMS-2020 quadrupole mass spectrometer and by calculating total phenolic content (TPC). For the first time, the antioxidant and antidiabetic activities of both leaves and fruit were determined using DPPH radical scavenging. The aqueous extract was indicated to have higher antioxidant activities than ethyl acetate and methanol extracts. The individual constituents within the different extracts for both fruit and leaves were detected as the luteolin-7-O-glucoside in the ethyl acetate (854 μg · g–1 and 1,098 μg · g–1), methanol (1,241 μg · g–1 and 2,136.43 μg · g–1) and aqueous (509 μg · g–1 and 898.23 μg · g–1) extracts, respectively. Extractions of ethyl acetate and methanol demonstrated stronger inhibitory activity against human salivary α-amylase than the aqueous extract of both parts of the mock privet. Similarly, extraction of ethyl acetate from the leaves and fruit of the mock privet indicated significantly better inhibitory activity than the methanol and aqueous extracts, respectively, for the inhibition of α-glucosidase activity. This study indicates that both fruit and leaves of mock privet may use as a potential source of natural biomolecules to promote healthy activities.

Capsicum annuum L. cv. DANGJO ameliorated hyperglycemia in type 2 diabetes animal model induced by high-fat diet and streptozotocin

In this study, it was evaluated the effect of freeze-dried powder of Capsicum annuum L. cv. DANGJO (DJ) on ameliorating hyperglycemia in type 2 diabetes rat model induced by high-fat diet (HFD) and streptozotocin (STZ). Oral administration of DJ significantly reduced non-fasting blood glucose (NFBG) and insulin levels, as well as glycated hemoglobin (HbA1c) level, a representative marker for diabetes, in HFD/STZ treated rats whereas the administration of green hot pepper (GHP) and green sweet pepper (GSP) did not show the significant effect. Quercitrin was quantified (40.97 mg/100 g of DJ) by HPLC, and administration of the same amount of quercitrin with DJ exerted the significant reduction of blood glucose level, strongly supporting that quercitrin is the key component in ameliorating the hyperglycemia of DJ in HFD/STZ treated rats. These results suggest that DJ can be considered as a potent functional food in preventing hyperglycemia in type 2 diabetes mellitus.

Identification of α-Glucosidase Inhibitors from Leaf Extract of Pepper (Capsicum spp.) through Metabolomic Analysis

Metabolomics and in vitro α-glucosidase inhibitory (AGI) activities of pepper leaves were used to identify bioactive compounds and select genotypes for the management of type 2 diabetes mellitus (T2DM). Targeted metabolite analysis using UPLC-DAD-QToF-MS was employed and identified compounds that belong to flavone and hydroxycinnamic acid derivatives from extracts of pepper leaves. A total of 21 metabolites were detected from 155 samples and identified based on MS fragmentations, retention time, UV absorbance, and previous reports. Apigenin-O-(malonyl) hexoside, luteolin-O-(malonyl) hexoside, and chrysoeriol-O-(malonyl) hexoside were identified for the first time from pepper leaves. Pepper genotypes showed a huge variation in their inhibitory activity against α-glucosidase enzyme(AGE) ranging from 17% to 79%. Genotype GP38 with inhibitory activity of 79% was found to be more potent than the positive control acarbose (70.8%.). Orthogonal partial least square (OPLS) analyses were conducted for the prediction of the AGI activities of pepper leaves based on their metabolite composition. Compounds that contributed the most to the bioactivity prediction model (VIP >1.5), showed a strong inhibitory potency. Caffeoyl-putrescine was found to show a stronger inhibitory potency (IC₅₀ = 145 µM) compared to acarbose (IC₅₀ = 197 µM). The chemometric procedure combined with high-throughput AGI screening was effective in selecting polyphenols of pepper leaf for T2DM management.

Identification of QTLs Controlling α-Glucosidase Inhibitory Activity in Pepper (Capsicum annuum L.) Leaf and Fruit Using Genotyping-by-Sequencing Analysis

Diabetes mellitus, a group of metabolic disorders characterized by hyperglycemia, is one of the most serious and common diseases around the world and is associated with major complications such as diabetic neuropathy, retinopathy, and cardiovascular diseases. A widely used treatment for non-insulin-dependent diabetes is α-glucosidase inhibitors (AGIs) such as acarbose, which hinders hydrolytic cleavage of disaccharides and retard glucose absorption. The ability to inhibit α-glucosidase activity has been reported in leaf and fruit of pepper (Capsicum annuum L.). In this study, we aimed to identify quantitative trait loci (QTLs) controlling α-glucosidase inhibitory activity (AGI activity) in pepper leaf and fruit using enzyme assay and genotyping-by-sequencing (GBS) analysis. The AGI activity at three stages of leaf and one stage of fruit development was analyzed by 96 F2 individuals. GBS analysis identified 17,427 SNPs that were subjected to pepper genetic linkage map construction. The map, consisting of 763 SNPs, contained 12 linkage groups with a total genetic distance of 2379 cM. QTL analysis revealed seven QTLs (qAGI1.1, qAGI11.1, qAGI5.1, qAGI9.1, qAGI12.1, qAGI5.2, and qAGI12.2) controlling AGI activity in pepper leaf and fruit. The QTLs for AGI activity varied by plant age and organ. This QTL information is expected to provide a significant contribution to developing pepper varieties with high AGI activity.

Alpha Glucosidase Inhibitory Activities of Plants with Focus on Common Vegetables

Type-2 diabetes mellitus is one of the most prevalent metabolic diseases in the world, and is characterized by hyperglycemia (i.e., high levels of glucose in the blood). Alpha-glucosidases are enzymes in the digestive tract that hydrolyze carbohydrates into glucose. One strategy that has been developed to treat type-2 diabetes is inhibition of the activity of alpha-glucosidases using synthetic drugs. However, these inhibitors are usually associated with gastrointestinal side effects. Therefore, the development of inhibitors from natural products offers an alternative option for the control of hyperglycemia. In recent years, various studies have been conducted to identify alpha-glucosidases inhibitors from natural sources such as plants, and many candidates have transpired to be secondary metabolites including alkaloids, flavonoids, phenols, and terpenoids. In this review, we focus on the alpha-glucosidases inhibitors found in common vegetable crops and the major classes of phytochemicals responsible for the inhibitory activity, and also as potential/natural drug candidates for the treatment of type-2 diabetes mellitus. In addition, possible breeding strategies for production of improved vegetable crops with higher content of the inhibitors are also described.