Stimulation of health-promoting triterpenoids accumulation in Centella asiatica (L.) Urban leaves triggered by postharvest application of methyl jasmonate and salicylic acid elicitors

摘要

Centella asiatica (L.) Urban is an important medicinal herb and has great potential in herbal industry. Its major bioactive triterpenoids possess wound healing, anti-aging, and anti-inflammation properties. One of the most important strategies to increase the production of secondary metabolites in plants is exogeneous elicitors. In this study, we quantified triterpenoid contents, anti-inflammatory activities, and assessed the transcription level expression of triterpenoid biosynthesis genes in C. asiatica leaves elicited with methyl jasmonate (MeJA) and salicylic acid (SA). The results showed that the total triterpenoid contents in C. asiatica leaves were significantly increased 2-fold over the control group after 2 mM SA treatment in all duration times, whereas MeJA treatment leaves were maximally enhanced 1.4-fold at 2 mM concentration for 40 min. The higher triterpenoid contents in C. asiatica leaves might be the result of overexpression of key genes in biosynthesis pathway after MeJA and SA treatments. Some experimental designs of MeJA and SA treatment enhanced the activity of phenylalanine ammonia-lyase (PAL) and antioxidant enzyme, including peroxidase (POD) and catalase (CAT). The represented leaves elicited by MeJA and SA, 2 mM at 60 min and 4 mM at 120 min, efficiently inhibited nitric oxide (NO) production in LPS-stimulated RAW 264.7 macrophage cells. These results related to the transcription level expression of iNOS in a dose-dependent manner. Our results suggest that MeJA and SA would be an exogenous elicitor to enhance the triterpenoid contents after the postharvest process and increase anti-inflammatory activity in LPS-stimulated RAW 264.7 cells.