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.Plants 2020, 9, 2 2 of 17 potential α-glucosidase inhibitors (AGIs) have been extensively screened or studied and acarbose, miglitol, voglibose, and 1-deoxynojirimycin (DNJ) are currently commercialized anti-glucosidase drugs (Figure 1; [7]) against type-2 diabetes, a chronic condition in which the body becomes resistant to the normal effects of insulin, resulting in ineffectiveness at managing the blood glucose levels.

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Phytophthora capsici Leonian, an oomycete pathogen, is a serious problem in pepper worldwide. Its resistance in pepper is controlled by quantitative trait loci (QTL). To detect QTL associated with P. capsici resistance, a molecular linkage map was constructed using 100 F(2) individuals from a cross between Capsicum annuum 'CM334' and C. annuum 'Chilsungcho'. This linkage map consisted of 202 restriction fragment length polymorphisms (RFLPs), 6 WRKYs and 1 simple sequence repeat (SSR) covering 1482.3 cM, with an average interval marker distance of 7.09 cM. QTL mapping of Phytophthora root rot and damping-off resistance was performed in F(2:3) originated from a cross between resistant Mexican landrace C. annuum 'CM334' and susceptible Korean landrace C. annuum 'Chilsungcho' using composite interval mapping (CIM) analysis. Four QTL explained 66.3% of the total phenotypic variations for root rot resistance and three 44.9% for damping-off resistance. Of these QTL loci, two were located close to RFLP markers CDI25 on chromosome 5 (P5) and CT211A on P9. A bacterial artificial chromosome (BAC) library from C. annuum 'CM334' was screened with these two RFLP probes to obtain sequence information around the RFLP marker loci for development of PCR-based markers. CDI25 and CT211 probes identified seven and eight BAC clones, respectively. Nine positive BAC clones containing probe regions were sequenced and used for cytogenetic analysis. One single-nucleotide amplified polymorphism (SNAP) for the CDI25 locus, and two SSRs and cleaved amplified polymorphic sequence (CAPS) for CT211 were developed using sequences of the positive BAC clones. These markers will be valuable for rapid selection of genotypes and map-based cloning for resistance genes against P. capsici.

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Transcriptome from high throughput sequencing-by-synthesis is a good resource of molecular markers. In this study, we present utility of massively parallel sequencing by synthesis for profiling the transcriptome of red pepper (Capsicum annuum L. TF68) using 454 GS-FLX pyrosequencing. Through the generation of approximately 30.63 megabases (Mb) of expressed sequence tag (EST) data with the average length of 375 base pairs (bp), 9,818 contigs and 23,712 singletons were obtained by raw reads assembly. Using BLAST alignment against NCBI non-redundant and a UniProt protein database, 30% of the tentative consensus sequences were assigned to specific function annotation, while 24% returned alignments of unknown function, leaving up to 46% with no alignment. Functional classification using FunCat revealed that sequences with putative known function were distributed cross 18 categories. All unigenes have an approximately equal distribution on chromosomes by aligning with tomato (Solanum lycopersicum) pseudomolecules. Furthermore, 1,536 high quality single nucleotide discrepancies were discovered using the Bukang mature fruit cDNA collection (dbEST ID: 23667) as a reference. Moreover, 758 simple sequence repeat (SSR) motif loci were mined from 614 contigs, from which 572 primer sets were designed. The SSR motifs corresponded to di- and tri- nucleotide motifs (27.03 and 61.92%, respectively). These molecular markers may be of great value for application in linkage mapping and association mapping research.