Effect of light quality on rosmarinic acid content and antioxidant activity of sweet basil, Ocimum basilicum L.

Abstract

Rosmarinic acid (RA), one of the main phenolic compounds in sweet basil (Ocimum basilicum L.), has antiviral, antimicrobial, and anti-inflammatory pharmacological properties. As recent studies have shown that UV-B and blue light irradiation stimulate phenylpropanoid biosynthesis, we determined whether light conditions affect RA content and antioxidant activity. Both antioxidant activity and phenolic content were increased by continuous white light irradiation. Ultra performance liquid chromatography analysis of the phenolic content of a methanolic extract of sweet basil revealed the presence of RA, caffeic acid and chicoric acid. Red and white light irradiation induced RA accumulation up to a level of 6mgg-1 fresh weight within 14 days, whereas blue light irradiation only induced RA accumulation up to a level of 3mg g-1 fresh weight, suggesting that the red wavelength at 600-700 nm in both white and red irradiation promoted the RA accumulation. In addition, RA accumulation was dependent on the irradiation period and was greater in the upper leaves than in the lower leaves. These results indicate that continuous white light is effective in increasing the RA content of basil, which results in high antioxidant activity.