The Influence of Red and Blue Light Ratios on Growth Performance, Secondary Metabolites, and Antioxidant Activities of Centella asiatica (L.) Urban

This study aimed to determine the optimal light conditions for the protected cultivation of Centella asiatica—a herbaceous medicinal plant with high bioactive content and antioxidant potential. The growth, triterpene glycoside content, total phenol content (TPC), total flavonoid content (TFC), and antioxidant activities of seedlings grown for five weeks under different light intensities (150 and 200 µmol m⁻² s⁻¹) and qualities (red and blue light ratios: 10:0, 8:2, and 6:4) were evaluated. Light intensity and quality significantly affected the studied parameters. At 150 µmol m⁻² s⁻¹ photosynthetic photon flux density (PPFD), most growth parameters decreased as the blue light ratio increased; however, the plants showed extreme epinasty under the sole red light treatment. Growth performance was highest under 20% blue light and 200 µmol m⁻² s⁻¹ PPFD. At both light intensities, the total triterpene glycoside content was higher for the sole red light and 20% blue light treatments than the 40% blue light treatment. Moreover, the TPC, TFC, and antioxidant activity increased as the blue light ratio increased. In conclusion, artificial light conditions affect the growth and secondary metabolite production of C. asiatica differentially, and 20% blue light at a higher light intensity (200 µmol m⁻² s⁻¹) is optimum for growing C. asiatica.