Exploring the nutritional biochemical profiles and biological functions in the green microalga Chlorella fusca

<i>Chlorella</i> species of microalgae are utilized in the crop and food industries. The aim of this research was to investigate the metabolite profiles of <i>Chlorella fusca</i> for the first time and evaluate its biological properties. The two ion modes of UPLC-Q-TOF-MS/MS were used to identify a total of 62 components in the methanol extract of <i>C. fusca</i>, with 26 in the negative and 36 in the positive ion mode, including 10 identical ingredients. Fatty acids (negative mode) and combinations of chlorophyll and fatty acids (positive mode) were the most prevalent chemical structures, constituting over 80 and 70% of the total metabolites, respectively, followed by chlorophyll, polar lipids, carotenoids, and fatty alcohols. Moreover, this extract exhibited potent antioxidant and anti-aging benefits in decreasing order of potency at a concentration of 200 μg mL<sup>-1</sup>: tyrosinase inhibition (100%), ABTS radical scavenging (90%), elastase inhibition (88%), and DPPH radical scavenging (34%). Notably, this extract protected the mobility of DNA fragments up to 5 μg mL<sup>-1</sup> (26%), with potential effects (> 60% at 200 μg mL<sup>-1</sup>). These findings suggest that <i>C. fusca</i> may be a promising candidate for applications related to its biological functions, owing to the high accumulation of fatty acids and chlorophyll derivatives.