Analysis of the Mycosporine-Like Amino Acid (MAA) Pattern of the Salt Marsh Red Alga Bostrychia scorpioides

Abstract

This study presents the validation of a high-performance liquid chromatography diode array detector (HPLC-DAD) method for the determination of different mycosporine-like amino acids (MAAs) in the red alga Bostrychia scorpioides. The investigated MAAs, named bostrychines, have only been found in this specific species so far. The developed HPLC-DAD method was successfully applied for the quantification of the major MAAs in Bostrychia scorpioides extracts, collected from four different countries in Europe showing only minor differences between the investigated samples. In the past, several Bostrychia spp. have been reported to include cryptic species, and in some cases such as B. calliptera, B. simpliciuscula, and B. moritziana, the polyphyly was supported by differences in their MAA composition. The uniformity in the MAA composition of the investigated B. scorpioides samples is in agreement with the reported monophyly of this Bostrychia sp.

Isolation and Structure Elucidation of Novel Mycosporine-like Amino Acids from the Two Intertidal Red Macroalgae Bostrychia scorpioides and Catenella caespitosa

“…The two amino acid residues of the side chains of this MAA have already been observed individually in other MAAs; glutamine has been found in MAAs from B. scorpioides-for example, in bostrychines A and B [6], while threamine is a constituent of the MAAs aplysiapalythine A and bostrychine E [6,28]. The advanced Marfey's method, an established LC-MS (Liquid Chromatography-Mass Spectrometry)-based procedure for determining the absolute configuration, has confirmed the presence of L-glutamic acid and R-threamine as constituent of other MAAs in this species [7]. In order to determine the absolute stereochemistry of C-5, geometrical optimization followed by ECD (Electronic Circular Dichroism) calculation at the m062x/6−31 + g(d,p)/smd//wb97xd/6−31 + g(d,p) level in H 2 O resulted in an ECD spectrum showing a high similarity to the experimentally obtained spectrum.…”

“…An HMBC correlation of proton H-9 (δ H 3.51) to carbon C-1 at δ C 163.4 indicated at which position the 4aminobutanamide moiety is attached to the cyclohexenimine scaffold. The advanced Marfey's method of bostrychines B, D and F has shown the presence of L-threonine as a constituent of the final product of the reaction, indicating that this amino acid residue in the MAA has an L-configuration [7]. The determination of the absolute stereochemistry of compound 2 by geometrical optimization followed by ECD calculation at the m062x/6−31 + g(d,p)/smd//wb97xd/6−31 + g(d,p) level in H 2 O resulted in an ECD spectrum showing an excellent match with the experimentally obtained spectrum, therefore establishing the absolute configuration as 5R,1 S,3 R. Compound 2 was finally identified as a new MAA, (2S,3R)-2-(((R,1E,3E)-3-((4-amino-4-oxobutyl)-l4-azaneylidene)-5-hydroxy-5-(hydroxymethyl)-2-methoxycyclohexan-2-ylium-1-ylidene)-l4-azaneyl)-3-hydroxybutanoate, for which we propose the trivial name bostrychine H. Compound 2 was assigned the molecular formula C16H27N3O7, as established by a positive ion (for [M + H] + , m/z = 374.1913; calculated for C16H28N3O7, 374.1927) in the HR-MS (High-Resolution-Mass Spectrometry) spectrum.…”

“…An HMBC correlation of proton H-9 (δH 3.51) to carbon C-1 at δC 163.4 indicated at which position the 4-aminobutanamide moiety is attached to the cyclohexenimine scaffold. The advanced Marfey's method of bostrychines B, D and F has shown the presence of ʟ-threonine as a constituent of the final product of the reaction, indicating that this amino acid residue in the MAA has an ʟ-configuration [7]. The determination of the absolute stereochemistry of compound 2 by geometrical optimization followed by ECD calculation at the m062x/6−31 + g(d,p)/smd//wb97xd/6−31 + g(d,p) level in H2O resulted in an ECD spectrum showing an excellent match with the experimentally obtained spectrum, therefore establishing the absolute configuration as 5R,1′S,3′R.…”

“…Drugs 2023, 21, 543 2 of 15 compounds [2]. Additionally, B. scorpioides produces a set of unique mycosporine-like amino acids (MAAs), bostrychines A to F (approximately 2-10 mg/g of dry weight in total) [6,7], compounds with established photoprotective but questionable osmoprotective properties [8]. Because of its high number of representatives of this compound class (eight to twelve MAAs), it stands out among other red algae of the same biogeographic region [9] or other Bostrychia species from all over the world.…”

Fast and Efficient Separation of Eleven Mycosporine-like Amino Acids by UHPLC-DAD and Their Quantification in Diverse Red Algae

“…The interest in MAAs has been steadily growing since their discovery in 1960 [22], and efficient methods for their qualitative and quantitative determination are required, especially as the literature reports on significant geographic and seasonal variations in the MAA content even within the same species or genus [1,4,[23][24][25]. Until now, the analysis of MAAs has been primarily conducted by conventional HPLC using reversed-type stationary phases [1,4,26,27] or HILIC material [2,23].…”