Stevioside glycoside-producing endophyte <i>Acremonium sclerotigenum</i> CBS 124.42 isolated from leaf tissue of <i>Stevia rebaudiana</i> (Bertoni) Bertoni and characterization by UHPLC-ESI-MS

<i>Stevia rebaudiana</i>, belonging to the Asteraceae family, was authenticated by the Botanical Survey of India, Kolkata. Molecular and taxonomic identification using 18S rRNA primers confirms the presence of a fungal endophyte, <i>Acremonium sclerotigenum</i> CBS 124.42, based on nucleotide homology and phylogenetic analysis. The fungal extract displayed strong antioxidant activity, with Superoxide Dismutase at 78.9 ± 3.01 μg/g, Catalase at 319.7 ± 2.05 μg/g, Phenylalanine Ammonia‑Lyase at 76 ± 1.63 μg/g, Radical Scavenging Assay (IC50) at 28.1 ± 6.96 mg/g, and FRAP at 27.6 ± 0.68 μM. Chemical analysis confirmed that <i>A. sclerotigenum</i> CBS 124.42 produces stevioside identical to the standard compound. UV‑Vis spectroscopy showed a λ_max of 210 nm for both the standard and endophytic extracts. UHPLC‑ESI‑MS revealed a peak area of 34.2 mAU/min for the endophyte, nearly double that of the standard (16.9 mAU/min), indicating higher compound abundance. Stevioside concentration in the endophytic extract was determined to be 1.94 mg/ml, four times greater than in regenerated callus (0.451 mg/ml) and six times higher than in plant leaf extract (0.274 mg/g). ESI‑MS analysis further confirms the identity, with a mass‑to‑charge ratio of 803.49 m/z, closely matching the standard stevioside (803.40 m/z). These findings highlight <i>A. sclerotigenum</i> CBS 124.42 as a promising alternative source for stevioside production, offering a sustainable and efficient bioproduction platform and its applicability in pharmaceutical and nutraceutical industries.