Exploring the Antiviral, Antioxidant Potentials, and UPLC-MS/MS Characterization of Stenotrophomonas maltophilia GMM Methanolic Extract

As a secondary metabolite with antioxidant and antiviral properties, microbial methanolic extract has drawn a lot of attention from researchers lately for its potential therapeutic applications. Therefore, in this study, a bacterium was isolated from the air in our lab at NRC Egypt, and this isolate is characterized by the production of faint orange methanolic extract and by using 16sRNA as Stenotrophomonas maltophilia GMM. The culture of our isolate was grown by solid surface fermentation on nutrient agar supplemented with 5% glycerol in order to produce crude methanolic extract. The antioxidant and antiviral activities of the extract was also assessed after it was extracted from the cells using methanol. A precise physicochemical characterization was carried out for the methanolic extract (MEGMM) using UPLC/ESI-qTOF-HRMS/MS technique. It is resulted in the identification of 28 major bioactive metabolites with a high structural diversity. Their structures confirmed as 12 organic bases, 6 aminoacid derivatives, 5carboxylic and long chain fatty acids, 3 phenolic derivatives, one sugar, and a long chain alkyl p-benzoquinone depending on matching of the major parameters, i.e. Rt-values, monoisotopic masses of the molecular and specific fragment ions and their relative abundances with conventional databases and literature. The results showed that the MEGMM has antioxidant activity ranged from 21.3 - 92.8 % using DPPH assay at different concentrations 1.25- 6.25 mg/ml and different time 30 - 120 min, with an IC50 of 2.5 mg/ml at 90 min. The MEGMM exhibited significant antiviral activity, with a 74.92% inhibition of HAV and a weaker activity of 41.89% against HSV-1 at 500 µg/ml. In terms of effective concentration (EC50), MEGMM showed potent activity against HAV (EC50 = 106.52 μg/mL), compared to amantadine as a reference drug (EC50 = 5.67 μg/mL). The results proved that the MEGMM has safety toward normal cells.