Onosma bracteatum is medicinal plant owning bioactive and medicinal properties. This study focuses on phytochemical screening, flavonoids and polyphenolic estimation, and to investigate the antiviral, antioxidant, antibacterial activities and In-silico Docking studies of Onosma bracteatum.

The methanol and DCM extracts of leaves, stems, and flowers were prepared, and their percentage yield was calculated. OBLM had the highest TFC (28.39 mg Qu. Eq/gm E) and TPC (191.43 mg GA. Eq/gm E). The antiviral activity assessed against IBV, NDV, and AIV H9N2. The HA and IC50 values of the extracts and the standard drug acyclovir were measured and reported respectively, OBSM fraction showed moderate antiviral activity against IBV, while OBLM and OBLD fractions had moderate activity against NDV. Acyclovir had the highest antiviral activity. None of the extracts showed activity against AIV H9N2. OBSM fraction showed higher antioxidant activity (219.65 mg AE. g-1 extract), followed by OBLM (74.90 mg AE. g-1 extract) and OBFM (40.81 mg AE. g-1 extract). The antibacterial activity of the methanol and DCM extracts of leaves, stems, and flowers was evaluated against E. coli, B. bronchiseptica, B. pumilus, and S. epidermidis. OBLM fraction had moderate activity against E. coli and B. pumilus (4.43 and 4.34 mm zones of inhibition, respectively). OBSM fraction had moderate activity against B. bronchiseptica (3.89 mm zone of inhibition). The standard, ciprofloxacin had strong antibacterial activity against all strains. The GC/MS analysis the extract revealed the presence of alkane, fatty acids, and esters. Methanol extract of flowers (OBFM) revealed the presence of three additional compounds: docosanoic acid, eocosyl ester, trans-2,4-dimethylthiane, S, S-dioxide, and cyclohexene, 1-methyl-3-(1-methylethenyl)-, (. +/-.)-. Finally, In-silico Docking studies were done to observe Binding Affinity and intermolecular interactions of methanolic extract with lipoxygenase, Nitric oxide synthase, xanthine oxidase enzyme.

The study revealed that Onosma bracteatum possesses promising antiviral, antioxidant, and antibacterial activities, which may be attributed to its phytochemical constituents. This comprehensive analysis suggested the possibility of novel drug candidates from this medicinal plant.

Key Words: Antioxidant, Antimicrobial, Flavonoids. GCMS, Onosma bracteatum