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In spray application contexts, plant leaves are bent and twisted upon droplet impact, which has a significant impact on the droplet’s impact behavior and its deposition effect on the leaves. This study examines the impact behavior of droplets on flexible pepper leaves and develops a mathematical model for droplet spreading and rebound, integrating the effects of leaf bending and torsion via energy conservation and cantilever beam theory. The energy required for leaf bending and twisting due to droplet impact was estimated in accordance with Hooke’s law. The droplets attained their maximum spreading diameter 4 ms post-impact on flexible pepper leaves, with droplet retraction occurring significantly faster on flexible leaves than on rigid ones, resulting in a return to steady state in half the duration required by rigid leaves. This study aims to establish a scientific foundation for optimizing pesticide application strategies and selecting parameters for spraying equipment in pepper production.

The ability to quickly and non-destructively monitor the cadmium (Cd) content in agricultural crops is the basic premise of effective prevention and control of Cd contamination in agricultural products. Hyperspectral technology provides a solution for this issue. The potential capability for the spectral prediction of the Cd content in the leaves of pepper and eggplant in the field was explored, and a spectral prediction model of the Cd content in these leaves was established. In this study, based on the indoor spectrum, the sensitive wavebands for predicting the Cd content in leaves were determined preliminarily by correlation analysis. Partial least squares regression (PLSR) and support vector machine regression (SVMR) were used to establish spectral prediction models, and the final sensitive wavebands were determined by the size of the model index. The results show that the SVMR model exhibited higher prediction accuracy than the PLSR model. The RPDp (relative percent different of prediction set) values of the best SVMR prediction models for the pepper leaves and the eggplant leaves were 1.82 and 1.49, respectively. The values of Rp2 (coefficient of determination of prediction set), which can quantitatively estimate the Cd content in leaves, were 0.897 (p < 0.01) and 0.726 (p < 0.01), respectively. This study demonstrated that the leaf spectra of pepper and eggplant in the field can be used to predict the Cd content in leaves, providing a reference for monitoring the Cd content in the fruits of pepper and eggplant in the future.

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.

To determine the optimum parameters for extracting three carotenoids including zeaxanthin, lutein epoxide, and violaxanthin from pepper leaves by response surface methodology (RSM), a solvent of acetone and ethyl acetate (1:2) was used to extract carotenoids with four independent factors: ultrasound time (20–60 min); ratio of sample to solvent (1:12–1:4); saponification time (10–50 min); and concentration of saponification solution (KOH–methanol) (10–30%). A second-order polynomial model produced a satisfactory fitting of the experimental data with regard to zeaxanthin (R2 = 75.95%, p < 0.0197), lutein epoxide (R2 = 90.24%, p < 0.0001), and violaxanthin (R2 = 73.84%, p < 0.0809) content. The optimum joint extraction conditions of zeaxanthin, lutein epoxide, and violaxanthin were 40 min, 1:8, 32 min, and 20%, respectively. The optimal predicted contents for zeaxanthin (0.823022 µg/g DW), lutein epoxide (4.03684 µg/g dry; DW—dry weight), and violaxanthin (16.1972 µg/g DW) in extraction had little difference with the actual experimental values obtained under the optimum extraction conditions for each response: zeaxanthin (0.8118 µg/g DW), lutein epoxide (3.9497 µg/g DW), and violaxanthin (16.1590 µg/g DW), which provides a theoretical basis and method for cultivating new varieties at low temperatures and weak light resistance.

Two lactic acid bacteria (LAB), Lactobacillus homohiochii JBCC 25 and L. homohiochii JBCC 46, were isolated from a naturally fermented vinegar beverage. Fermented pepper leaves beverage (FPLB-3) which indicated good assessment based on a sensory evaluation test was prepared using the mixed strains. The prepared FPLB-3 showed enhanced functional aspects based on γ-aminobutyric acid (23.6 mg%), total polyphenol (2,828.2 gallic acid equivalents μg/g), and flavonoid contents (2,008.8 catechin equivalents μg/g). Moreover, FPLB-3 showed significantly stronger scavenging activities for the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (84.6%) and superoxide radical (90.8%) and outstanding inhibitory activity against α-glucosidase of 65.9% at 50 mg/mL compared to the raw material. Based on the results, the newly developed FPLB using Wongi-1 pepper leaves and Lactobacillus is expected to be a novel functional food with natural antioxidant and antidiabetic capacities.

Although pepper leaves have been consumed as a traditional folk food in Korea, chemopreventive researches on pepper leaves are very rare. Thus, chemopreventive activity of pepper leaves was evaluated by isolating active compounds from pepper leaves. The methanol extract of pepper leaves showed significantly strong quinone reductase (QR) inductive activity compared to that of broccoli. Through partition and column chromatography, two major QR inducers were isolated from pepper leaves. Based on visible spectra, thin layer chromatography, solubility, chemical reactions, and DIP-MS, two major QR inducers from pepper leaves were identified as lutein and β-carotene. The concentration required to double the specific activity of QR (CD) values of lutein and β-carotene were 87.5 and 10.0 μM, respectively.

The size, shape and number of starch grains have been determined in mature pepper leaves taken from plants grown under defined conditions of daylength and irradiance. Starch grains were 0.2–7.0 μm diameter and 02–1.5 μm in thickness. Grain diameter was positively related to daylength and the number of grains per unit leaf area inversely related to daylength. Mean grain diameter was also positively related to leaf area. Analysis of starch grains from leaves having a wide range of starch contents showed that grain diameter was linearly related to leaf starch content. However, mean diameter only doubled with a 10-fold increase in starch content. The number of grains increased from approximately 5 × 1010 m−2 of leaf to over 200 × 1010 m−2 with increasing starch content. The total surface area of grains increased from less than 1.0 m2 m−2 leaf to over 20 m2 m−2 leaf. Leaf starch grain shape and size are compatible with both efficient storage as disc-shaped chloroplasts and the maintenance of high total grain surface area by increasing grain number more than diameter. Possible mechanisms for the control of grain initiation, growth and degradation are suggested.

The chili pepper (Capsicum annuum L.) is a food source that is rich in flavonoids such as luteolin and apigenin. Flavonoids are known to have anti-inflammatory and antioxidant activities; however, studies on the flavonoids composition identified and the anti-inflammatory and antioxidant effects in pepper leaves (PL) and fruits (PF) are insufficient. In the present study, we investigated the antioxidant and anti-inflammatory effects in vitro, and the flavonoids contents of the PL and PF. Pepper extracts showed radical scavenging activities and ameliorated the lipopolysaccharide (LPS)-stimulated inflammatory response by decreasing nitric oxide production and interluekin-6 and tumor necrosis factor alpha levels in RAW 264.7 cells, with more effective activities noted for PL than for PF. Furthermore, PL extracts markedly inhibited the LPS-induced production of reactive oxygen species accumulation. The flavonoid profile and content of pepper were dependent on the part, with PL showing higher total flavonoids than PF. In particular, the content of luteolin glycosides in PL was twice that in PF. Thus, PL may be useful to prevent oxidative stress and inflammation-related diseases.

Pepper yellow leaf curl disease caused by begomoviruses has emerged as a major limitation to the cultivation of pepper (Capsicum spp.) production in a number of regions around the world. Although begomovirus resistance has been reported in several accessions, pepy-1 derived from BaPep-5 (C. annuum) is the only begomovirus resistance gene cloned to date. In this study, we evaluated the resistance of a C. chinense accession GR1 against pepper yellow leaf curl Indonesia virus (PepYLCIV), which is one of the predominant begomovirus species infecting pepper plants in Indonesia. Infection of PepYLCIV to susceptible Habanero (C. chinense) plants induced typical yellowing symptoms, whereas the GR1 plant showed symptoms with very low severity. Moreover, the accumulation of viral DNA was restricted in GR1 compared to Habanero. Phenotypic analyses of F1 and F2 populations obtained by crossing Habanero with GR1 inferred that the resistance is a dominant trait controlled by multiple genes. Linkage analysis in the F2 population using restriction site-associated DNA sequencing data detected two significant quantitative trait loci (QTLs), one on chromosome 4 and another on chromosome 11, which explained 31.6 and 19.7% of the phenotypic variation, respectively. Moreover, QTL-seq conducted using F3 population partially confirmed the result of F2 population, which detected QTLs on chromosome 3 and 11, respectively. The QTLs identified for PepYLCIV resistance in this research are novel since no other resistance causing QTLs have ever been reported in these genomic regions. GR1 is a highly valuable genetic resource for the breeding of begomovirus resistance in peppers.

Background The red (R) and blue (B) light wavelengths are known to influence many plant physiological processes during growth and development, particularly photosynthesis. To understand how R and B light influences plant photomorphogenesis and photosynthesis, we investigated changes in leaf anatomy, chlorophyll fluorescence and photosynthetic parameters, and ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) and Calvin cycle-related enzymes expression and their activities in sweet pepper ( Capsicum annuum L.) seedlings exposed to four light qualities: monochromatic white (W, control), R, B and mixed R and B (RB) light with the same photosynthetic photon flux density (PPFD) of 300 μmol/m 2 ·s. Results The results revealed that seedlings grown under R light had lower biomass accumulation, CO 2 assimilation and photosystem II (PSII) electron transportation compared to plants grown under other treatments. These changes are probably due to inactivation of the photosystem (PS). Biomass accumulation and CO 2 assimilation were significantly enriched in B- and RB-grown plants, especially the latter treatment. Their leaves were also thicker, and photosynthetic electron transport capacity, as well as the photosynthetic rate were enhanced. The up-regulation of the expression and activities of Rubisco, fructose-1, 6-bisphosphatase (FBPase) and glyceraldehyde-phosphate dehydrogenase (GAPDH), which involved in the Calvin cycle and are probably the main enzymatic factors contributing to RuBP (ribulose-1, 5-bisphosphate) synthesis, were also increased. Conclusions Mixed R and B light altered plant photomorphogenesis and photosynthesis, mainly through its effects on leaf anatomy, photosynthetic electron transportation and the expression and activities of key Calvin cycle enzymes.