LC-MS/MS-based metabolite profiling and functional assessment of Hydrodictyon reticulatum as a potential source of natural therapeutics collected from the Yamuna River, India

• Rich in carbohydrates, proteins, phenols, and flavonoids • Strong antioxidant and anti-diabetic activities detected • LC-MS/MS revealed diverse bioactive metabolites • High lipid content supports biodiesel potential • Mineral-rich biomass suitable for industrial applications Hydrodictyon , a filamentous green alga, was found across multiple sites in the Yamuna River, India, during COVID-19, forming harmful algal blooms. Its potential uses remain underexplored. This study investigates the nutraceutical, antioxidant, and antidiabetic properties of Hydrodictyon reticulatum collected from different locations. The metabolic analysis revealed the highest concentrations of carbohydrates in Haryana (24.29 ± 0.12%), reducing sugars in Baghpat (8.41 ± 0.22%), chlorophyll a in Baghpat (0.30 ± 0.06 mg/g DW), chlorophyll b in Baghpat and Katha (0.49 ± 0.08/0.02 mg/g DW), carotenoids in Baghpat (0.39 ± 0.01 mg/g DW), and flavonoids in Baghpat (13.07 ± 0.73 mg QE/g DW). The sample from Khekra exhibited the highest protein content (5.85 ± 0.13%) and phenolic content (117.57 ± 3.94 mg GAE/g DW). Lipid content, relevant for biodiesel applications, peaked in Haryana (31.47 ± 0.87%). The strongest antioxidant responses were observed for DPPH in Katha (86.45 ± 3.73%), TAC in Katha (411.80 ± 4.23 mg TAE/g DW), and FRAP in Katha (16.97 ± 0.55 µmol TE/g DW). For antidiabetic activity, the lowest (strongest) α-glucosidase IC₅₀ was recorded in Katha (0.09 ± 0.03 mg/ml), while the lowest α-amylase IC₅₀ occurred in Khekra (0.13 ± 0.01 mg/ml). LC-MS/MS analysis revealed a diverse array of bioactive compounds, including lipids, sterols, flavonoids, and phenolic acids. Combined LC-MS/MS, FTIR, and CHNS analyses highlight the antioxidant, anti-inflammatory, nutraceutical, and biodiesel potential of H. reticulatum from the Yamuna River.