PHYTOCHEMICAL ANALYSIS AND ANTIOXIDANT PROPERTIES OF BIOACTIVE COMPOUNDS FROM N-HEXANE EXTRACT OF BACTERIAL ENDOPHYTES FROM GINGER RHIZOMES

The search for novel therapeutic agents from natural sources has intensified interest in endophytic microorganisms inhabiting medicinal plants. Ginger (Zingiber officinale) is widely recognized for its diverse bioactive constituents, and its bacterial endophytes are increasingly regarded as complementary contributors to its pharmacological properties. This study investigated the phytochemical composition and antioxidant potential of bioactive compounds produced by bacterial endophytes isolated from Z. officinale. Fresh rhizomes were collected, authenticated, surface-sterilized, and processed for endophyte isolation. Three bacterial isolates, LE1 (Staphylococcus aureus), LE2 (Bacillus cereus), and LE3 (Serratia marcescens), were recovered and characterized through morphological and biochemical tests. Each isolate ( LE1, LE2, LE3 )underwent submerged fermentation, after which crude secondary metabolites were extracted using N-hexane. Qualitative and quantitative phytochemical analyses were conducted, and antioxidant activity was assessed using DPPH(2,2-Diphenyl-1-picrylhdrazyl), FRAP(Ferric Reducing Antioxidant Power), and total antioxidant capacity assays. High-Performance Liquid Chromatography (HPLC) profiling was performed to identify major bioactive compounds. The extracts contained diverse secondary metabolites including alkaloids, saponins, flavonoids, phenolics, cardiac glycosides, sterols, terpenoids, and cyanogenic glycosides. Local Endophyte1(Staphylococcus aureus) showed higher levels of alkaloids, flavonoids, and cardiac glycosides, and Local Endophyte3 (serratia marcescens) contained the highest saponin and sterol contents. Antioxidant assays revealed strong radical scavenging and ferric-reducing activity across all isolates, with DPPH inhibition reaching 75.8% (LE1) and FRAP values as high as 76.34 µM (LE2) at 400 µg/mL. Total phenolic content peaked in LE3 (15.51 mg GAE/g), whereas flavonoids were most abundant in LE1 (10.95 mg QE/g). HPLC analysis confirmed the presence of significant antioxidant compounds such as kaempferol, catechin, chlorogenic acid, corilagin, rutin, ellagic acid, and phosphorylcholine. The study demonstrates that ginger-associated bacterial endophytes produce abundant bioactive metabolites with strong antioxidant potential. These findings support their promise as sustainable sources of natural therapeutic compounds for pharmaceutical and nutraceutical applications.