Short-Term Pre-Harvest UV-B Supplement Enhances the Polyphenol Content and Antioxidant Capacity of Ocimum basilicum Leaves during Storage

Abstract

Ocimum basilicum (basil) leaves are rich in polyphenols, conferring them a high antioxidant activity. The application of UV-B can be used to maintain the post-harvest nutraceutical quality of basil leaves. We aimed to investigate the effects of pre-harvest UV-B application on polyphenolic and pigment contents, antioxidant capacity, and the visual quality of basil stored leaves. We also evaluated the applicability of the non-invasive Dualex® for monitoring the accumulation of leaf epidermal phenolics (Flav Index). After exposing plants to white light (control) and to supplemental UV-B radiation for 4 d, the leaves were harvested and stored for 7d (TS7). The UV-B leaves showed both a higher phenolic content and antioxidant capacity than the controls at TS7. In addition, the correlations between the Flav Index and phenolic content demonstrated that Dualex® can reliably assess the content of epidermal phenolics, thus confirming its promising utilization as a non-destructive method for monitoring the phytochemical quality of O. basilicum leaves. In conclusion, a pre-harvesting UV-B application may be a tool for enhancing the content of polyphenols and the antioxidant potential of basil stored leaves without detrimental effects on their visual quality. These results are important considering the nutraceutical value of this plant and its wide commercial distribution.

Quantitative Analysis of UV-B Radiation Interception in 3D Plant Structures and Intraindividual Distribution of Phenolic Contents

“…It was confirmed that the developmental age and intercepted UV-B level of each leaf co-determined the UV-B-induced accumulation of phenolics, and statistical analyses of each factor were possible through quantification of UV-B radiation interception. The short-term pre-harvest UV-B exposure improved phenolic contents without negative effects on growth and photosynthesis in kale, which is consistent with previous research in basil [41].…”

Effects of Nocturnal UV-B Irradiation on Growth, Flowering, and Phytochemical Concentration in Leaves of Greenhouse-Grown Red Perilla

“…In contrast, Goto et al [ 11 ] reported an increase in PA concentration after a short period of UV-B irradiation (3 days), depending on the duration of UV-B irradiation and the leaf growth stage. Furthermore, a correlation between the number of glandular trichomes, in which PA accumulate and PA concentration has been reported [ 16 ]. Indeed, UV-B radiation reduces the density of trichomes on the adaxial leaf surface, whereas it increases the number of trichomes on the abaxial leaf surface [ 29 ].…”

“…Previous studies conducted in growth chambers have reported that UV-B irradiation influences growth, development, PA, and RA concentration in red perilla plants [ 10 , 11 ]. Additionally, it has been reported that the concentration of certain phytochemicals increases with exposure to UV-B irradiation in other members of Lamiaceae [ 12 , 13 , 14 , 15 , 16 , 17 ].…”

Physiological, Biochemical and Molecular Assessment of UV-A and UV-B Supplementation in Solanum lycopersicum

“…UV-B 5 min increased Chl a and Chl b , supporting that UV-B stimulates the pathways involved in chlorophyll synthesis. Likewise, a short-term pre-harvest supplement of UV-B did not compromise the levels of Chl a , Chl b , or carotenoids in Ocimum basilicum leaves [ 26 ]. In tomato, the UV-B 5 min dose used stimulated the carotenoid pathways, supporting investment in these UV-protecting pigments and scavengers of reactive oxygen species (ROS), towards protecting chlorophylls from photo-oxidative damage caused by any excessive UV-B irradiation, as also proposed by Yadav et al [ 29 ].…”

“…UV-A light that ranges between 315 and 400 nm has beneficial effects on the growth and vigor of seedlings [ 10 ]. It also increases chlorophyll and carotenoid levels and stimulates polyphenol pathways and levels [ 26 , 27 ], thus it may be used to improve the yield and/or quality of crops. In this line, Lee et al [ 15 ] used LED UV-A to increase the biomass of kale plants.…”