Impact of Light Intensity on Antioxidant Activity of Tropical Microalgae

Abstract

Twelve microalgae species isolated in tropical lagoons of New Caledonia were screened as a new source of antioxidants. Microalgae were cultivated at two light intensities to investigate their influence on antioxidant capacity. To assess antioxidant property of microalgae extracts, four assays with different modes of action were used: 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-éthylbenzothiazoline-6-sulphonique) (ABTS), oxygen radical absorbance capacity (ORAC), and thiobabituric acid reactive substances (TBARS). This screening was coupled to pigment analysis to link antioxidant activity and carotenoid content. The results showed that none of the microalgae studied can scavenge DPPH and ABTS radicals, but Chaetoceros sp., Nephroselmis sp., and Nitzschia A sp. have the capacity to scavenge peroxyl radical (ORAC) and Tetraselmis sp., Nitzschia A sp., and Nephroselmis sp. can inhibit lipid peroxidation (TBARS). Carotenoid composition is typical of the studied microalgae and highlight the siphonaxanthin, detected in Nephroselmis sp., as a pigment of interest. It was found that xanthophylls were the major contributors to the peroxyl radical scavenging capacity measured with ORAC assay, but there was no link between carotenoids and inhibition of lipid peroxidation measured with TBARS assay. In addition, the results showed that light intensity has a strong influence on antioxidant capacity of microalgae: Overall, antioxidant activities measured with ORAC assay are better in high light intensity whereas antioxidant activities measured with TBARS assay are better in low light intensity. It suggests that different antioxidant compounds production is related to light intensity.

Effects of Nitrogen Availability on the Antioxidant Activity and Carotenoid Content of the Microalgae Nephroselmis sp

“…Our results showed a clear correlation between the peroxyl radical scavenging activity of the Nephroselmis sp. extract and the total carotenoid content ( Table 1 ), in agreement with our previous report [ 37 ]. Peroxyl radical scavenging is essential to protect cellular membranes against oxidative damage, since peroxyl radicals can start lipid peroxidation chain reactions [ 14 ].…”

“…Indeed, siphonaxanthin derivatives were found among all the Nephroselmis species studied by Yoshii et al [ 38 ], such as siphonaxanthin esters or methoxy siphonaxanthin. However, we did not find any siphonaxanthin derivatives for any culture conditions in our strain (present study and Coulombier et al [ 37 ]), and we could not classify it according to Yoshii et al’s classification [ 38 ]. Thus, we suggest that this species could belong to a sixth type that contains only siphonaxanthin and no siphonaxanthin derivatives.…”

“…In this study, we focus on the effects of nitrogen availability on the antioxidant activity and carotenoid content of Nephroselmis sp. It is a chlorophyte species isolated in a tropical lagoon in New Caledonia that was previously identified as a good source of natural antioxidant owing to its high carotenoid content [ 37 ]. In addition, Nephroselmis sp.…”

“…In addition, Nephroselmis sp. contains siphonaxanthin [ 37 , 38 ], an uncommon pigment of interest for biotechnological applications. Indeed, it was shown that this ketocarotenoid, which is mainly found in primitive green algae, has several bioactive properties, including antioxidant activity [ 39 ], but also antiangiogenic [ 40 ], antiobesity [ 41 , 42 , 43 ], anti-inflammatory [ 44 ], and apoptosis-inducing effect [ 45 ].…”

“…In a previous study, it was found that high light conditions induced an increase of carotenoid contents, including siphonaxanthin, as well as peroxyl radical scavenging activity on Nephroselmis sp. [ 37 ]. However, the effects of other culture parameters (e.g., pH, temperature, nutrient) on antioxidant activity and carotenoid contents, especially siphonaxanthin, have not yet been investigated in Nephroselmis sp.…”