As a fruit and vegetable crop, the ornamental pepper is not just highly ornamental but also rich in nutritional value. The quality of ornamental pepper fruits is given in their contents of capsaicin, vitamin C (VC), flavonoids and total phenols. The study concentrated on the accumulation of capsaicin and dihydrocapsaicin in different tissues of 18 peppers during fruit growth and development. The results showed that the pericarp and placenta contained significantly higher levels of capsaicin than dihydrocapsaicin. Additionally, the placenta contained significantly higher levels of both capsaicin and dihydrocapsaicin compared to the pericarp. The content of capsaicin was in the range of 0–6.7915 mg·g⁻¹, the range of dihydrocapsaicin content was 0–5.329 mg·g⁻¹. Interestingly, we found that the pericarp is rich in VC (5.4506 mg·g⁻¹) and the placenta is high in flavonoids (4.8203 mg·g⁻¹) and total phenols (119.63 mg·g⁻¹). The capsaicin is the most important component using the correlation analysis and principal component analysis. The qPCR results substantiated that the expression of genes in the placenta was significantly higher than that in the pericarp and that the expression of genes in green ripening stage was higher than that in red ripening stage. This study could be utilized to select the best ripening stages and tissues to harvest peppers according to the use of the pepper and to the needs of producers. It not only provides a reference for quality improvement and processing for consumers and market but also provides a theoretical basis for high-quality pepper breeding.

Pepper (Capsicum annuum L.), an annual herbaceous plant in the Solanaceae family, possesses significant edible and medicinal value. Studies have shown that there are significant differences in the plant chemical constituents and antioxidant activity among different colored peppers, but there have been fewer studies on the relationship between pigment content, plant chemical constituents and antioxidant activity in peppers. Therefore, this study divided twenty pepper accessions of pepper materials into four categories based on color changes and measured the bioactive compounds, pigment content and antioxidant activity of these four types of peppers at different maturity stages and conducted correlation analysis and principal component analysis (PCA). The results showed that yellow pepper cultivars had higher levels of vitamin C (Vc), and Class IV (purple-to-red transitioning pepper cultivars) had higher total phenolic content (TPC), total flavonoid content (TFC), and anthocyanin content in the early fruit stage. Correlation analysis showed that Class IV (purple-to-red transitioning pepper cultivars) had higher levels of bioactive compounds and antioxidant capacity. The antioxidant content in immature fruits was high, but decreased as the fruits matured. This study focuses on pepper-derived bioactive compounds and their antioxidant activity, providing a scientific basis for developing natural antioxidant products, expanding pepper resource utilization, and guiding pepper variety selection and cultivation management.