Chemical-analytical characterization and Pun1 gene expression variability analysis of ten selected Capsicum varieties

This study aimed to identify chilli pepper varieties with bioactive compounds that may enhance the anticancer properties of medium-chain triglyceride (MCT) oil. Ten chilli varieties cultivated in Slovakia were analysed for capsaicin (CAP), dihydrocapsaicin (DHC), capsaicin synthase (CS) expression, antioxidant activity (AA), and other bioactive compounds. CAP content ranged from 0.53 to 62.81 g/kg DW, with Carolina Reaper exhibiting the highest levels and Peito de Moca the lowest. A strong positive correlation between CAP and DHC (r = 0.987; p < 0.001) highlighted interconnected biosynthetic pathways. Carolina Reaper also showed the highest expression of the Pun1 gene (8.51-fold greater than in Habanero Red), correlating with its high CAP levels. Polyphenol content varied significantly, with rutin trihydrate reaching 211.63 mg/kg in Orange Coral. Total phenolic content (TPC) ranged from 7.51 to 25.07 mg GAE/g, highest in Carolina Reaper. Increased CAP production negatively correlated with trans-caffeic acid synthesis (r = −0.943; p < 0.05), while CS expression positively correlated with TPC (r = 0.806; p < 0.01) and capsaicinoids (CAP: r = 0.733; DHC: r = 0.745). AA ranged from 2.24 to 5.50 mg TEAC/g DW, with Carolina Reaper again showing the highest levels. These findings highlight the unique biochemical profile of Carolina Reaper, excelling in capsaicinoid production and antioxidant capacity. It will be utilized in future research exploring its potential to enhance the anticancer properties of MCT oil, which will be tested on human cancer cell lines. • Carolina Reaper had the highest CAP, DHC, and total capsaicinoid content. • Significant correlation found between Pun1 gene expression and capsaicinoid levels. • A strong trade-off observed between capsaicinoid and phenolic compound synthesis. • Variability in polyphenol content suggests diversity among chilli varieties. • Carolina Reaper showed the highest antioxidant capacity among the varieties studied.