Impact of UV-A and UV-C radiation to enhance triterpenoids and related gene expression in triterpenoid pathway of Centella asiatica postharvest

The objective of this investigation was to examine the impact of ambient UV-A and UV-C radiation on the triterpenoids, transcript level expression of enzymes within the biosynthesis pathway, and the anti-inflammatory property of Centella asiatica leaves at different times after postharvest. Leaves of C. asiatica were harvested without petiole and irradiated by UV-A and UV-C radiation for 2, 4, and 8 hours. UV-C radiation stimulated the highest synthesis of triterpenoid contents at 8 hours, while UV-A radiation showed the maximum bioactive compounds at 4 hours when compared with the control. Both experimental conditions elicited an enhancement in phenylalanine ammonia-lyase (PAL), catalase and peroxidase enzyme activities. The modified gene expression profiles of key enzymes, β-amyrin synthase, squalene synthase, farnesyl diphosphate synthase, and PAL in the biosynthetic pathway, potentially contribute to the higher content of triterpenoids observed in leaf treatments. The application of 8 hours of UV-C and 4 hours of UV-A to the chosen leaves resulted in a significant reduction in nitric oxide production in LPS-elicited RAW 264.7 cells compared to the control group. These findings exhibited a strong correlation with transcriptional expression of COX-2, IL-6 and iNOS in a dose-related manner. Our findings suggest that UV-A and UV-C radiation as abiotic stress is likely stimulated through the triterpenoid pathway after C. asiatica leaves postharvest and increased anti-inflammatory property in LPS-induced cells. Furthermore, UV radiation application showed a feasible short-time and affordable experimental price, as well as convenient methods to carry out.