GC-MS Analysis of Bioactive Compounds from the Ethanolic Extract of Halochlorella rubescens P. J. L. Dangeard, nom. inval., 1966

Microalgae contain chemically diverse metabolites that are of interest for biological and industrial applications. This study investigated the chemical constituents of an ethanolic extract of the green microalga Halochlorella rubescens using gas chromatography–mass spectrometry (GC–MS). The organism was isolated and identified using morphological examination and 18S rRNA-based molecular identification. Dried microalgal biomass was extracted with aqueous ethanol, and the resulting extract was analysed by GC–MS under electron-ionisation conditions. Compound assignments were made by comparing the observed mass spectra with library spectra and evaluating characteristic fragment ions. Three principal compounds were tentatively identified: neophytadiene at a retention time of 15.15 min, hexadecanoic acid methyl ester (methyl palmitate) at 15.70 min, and a polyunsaturated C18 fatty acid methyl ester, provisionally assigned as methyl linoleate, at 16.61 min. Methyl palmitate produced the strongest reported library agreement among the identified compounds, whereas the assignment of methyl linoleate remained tentative because of uncertainty in the library match. Additional chromatographic peaks showed poor spectral matches or features consistent with analytical artefacts and were not considered constituents of the extract. The findings indicate that the extract contains terpenoid- and fatty-acid-derived compounds of potential chemical and industrial interest. Confirmation using retention indices, authentic standards and additional analytical approaches is required before definitive identification and biological interpretation.