Seasonal Variation of Mycosporine-Like Amino Acids in Three Subantarctic Red Seaweeds

Abstract

UV-absorbing compounds, such as mycosporine-like amino acids (MAAs), are a group of secondary metabolites present in many marine species, including red seaweeds. In these organisms, the content and proportion of the composition of MAAs vary, depending on the species and several environmental factors. Its high cosmetic interest calls for research on the content and composition of MAAs, as well as the dynamics of MAAs accumulation in seaweeds from different latitudes. Therefore, this study aimed to survey the content of UV-absorbing MAAs in three Subantarctic red seaweeds during a seasonal cycle. Using spectrophotometric and HPLC techniques, the content and composition of MAAs of intertidal Iridaea tuberculosa, Nothogenia fastigiate, and Corallina officinalis were assessed. Some samples were also analyzed using high-resolution mass spectrometry coupled with HPLC-ESI-MS in order to identify more precisely the MAA composition. I. tuberculosa exhibited the highest MAA values (above 1 mg g^-1 of dried mass weight), while C. officinalis showed values not exceeding 0.4 mg g^-1. Porphyra-334 was the main component in N. fastigiata, whereas I. tuberculosa and C. officinalis exhibited a high content of palythine. Both content and composition of MAAs varied seasonally, with high concentration recorded in different seasons, depending on the species, i.e., winter (I. tuberculosa), spring (N. fastigiata), and summer (C. officinalis). HPLC-ESI-MS allowed us to identify seven different MAAs. Two were recorded for the first time in seaweeds from Subantarctic areas (mycosporine-glutamic acid and palythine-serine), and we also recorded an eighth UV-absorbing compound which remains unidentified.

Keywords: Corallina; Iridaea; Mycosporine-like amino acids; Nothogenia; red algae.

Figure 1

Photosynthetically Active Radiation (PAR: λ = 400–700 nm ) and UVR irradiances recorded at Bahía Mansa, Magellan Strait. UV-A (λ = 320–400 nm: dotted line), UV-B (λ = 290–320 nm: black solid line), and PAR values were obtained from the tropospheric ultraviolet visible model (TUV), considering measurements made around 17:00 h every 2 days during 2018.

Figure 2

Absorption characteristics (OD g⁻¹ DW) of 20% methanol extracts of Nothogenia fastigiata, Iridaea tuberculosa, and Corallina officinalis collected from Bahía Mansa, Magellan Strait, Chilean Patagonia, during summer, autumn, winter, and spring. Each curve is an average of five measurements.

Figure 3

Total mycosporine-like amino acid (MAA) content expressed as mg g⁻¹ DW (mean values ± SE, n = 3) in Nothogenia fastigiata (A), Iridaea tuberculosa (B), and Corallina officinalis (C) collected from Bahía Mansa, Magellan Strait, Chilean Patagonia, during summer, autumn, winter, and spring. Lowercase letters on the graph represent results of the Student Newman–Keuls Test (p <0.05); different letters refer to significant differences between mean values.

Figure 4

Percentages of palythine (grey bars), asterina-330 (plot points), shinorine (plot lines bars), porphyra-334 (white bars), and palythinol (black bars) (mean values, n = 3) in Nothogenia fastigiata (A), Iridaea tuberculosa (B), and Corallina officinalis (C) collected from Bahía Mansa, Magellan Strait, Chilean Patagonia, during summer, autumn, winter, and spring.