Comparative Untargeted LC-HRMS-Based Metabolomic Profiling of Gracilaria edulis (Gracilariales, Rhodophyta) from Three Different Beaches Using Sequential Solvent Extraction

Abstract

Gracilaria edulis, a red seaweed that is widely known as an agar-producing seaweed, has a unique biosynthetic pathway for producing bioactive compounds. However, most of the bioactive compounds of this species have not explored yet. The environmental conditions as well as the extraction method might influence the bioactive compound production. Hence, this study aimed to explore untargeted liquid chromatography–high resolution mass spectrometry (LCHRMS)-based metabolomics profiling of G. edulis (Gracilariales, Rhodophyta) from three different beaches along the southern part of the Special Region of Yogyakarta (Java Island, Indonesia), which has different environmental characteristics. We also observed the effect of extraction solvent on metabolomic profiling of G. edulis extract using three different solvents with the different polarity. Metabolomic profiling was performed using an LC-HRMS instrument and analyzed using the Global Natural Product Social Molecular Networking (GNPS) database. The results revealed differences in the metabolomic profiles of G. edulis’s extracts based on coastal location and solvent. G. edulis from Kukup Beach exhibited the highest metabolomic diversity (277 nodes), followed by G. edulis from Sepanjang Beach (268) and G. edulis from Krakal Beach (204). Among the solvents, n-hexane was the most effective, extracting 311 nodes, followed by methanol (293) and ethyl acetate (197). Nine tentatively dereplicated compounds were found, i.e., pumilacidine C, pumilacidine E, lichenysin, cholesterol, AC1L1X1Z, sarmentoside B, 7-dehydrocholesterol, pheophytin A and porphyra-334. Some dereplicated compounds were found in a specific area. For example, lichenysin and pumilacidin compounds were produced by G. edulis from Sepanjang Beach, while cholesterol and AC1L1X1Z were found in from G. edulis extract, which were collected from Sepanjang and Kukup Beaches, and 7-dehydrocholesterol and sarmentoside B compounds from all beach locations, while pheophytin A and porphyra-334 from Krakal Beach. Further research is needed to obtain pure compounds that have the potential to be antibacterial, as well as antioxidant, anti-inflammatory, and photoprotective compounds.

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