Endophytic Bacillus pacificus from Cissus quadrangularis L.: A Source of Bioactive Flavonoids and Terpenoids

Cissus quadrangularis L. is a renowned medicinal plant with established fracture-healing and antioxidant properties, often attributed to its phytochemicals. However, the role of its endophytic bacteria as a source of these bioactive compounds remains largely unexplored. This study aimed to isolate, characterize, and identify endophytic bacteria from C. quadrangularis stems and analyze their potential for producing therapeutic secondary metabolites.Endophytic bacteria were isolated from surface-sterilized stem segments of C. quadrangularis collected from Kerala, India. A predominant isolate (QS1) was characterized morphologically, biochemically, and via 16S rRNA gene sequencing. Secondary metabolites were extracted from the isolate using ethyl acetate and subjected to qualitative phytochemical screening and quantitative analysis of total flavonoid content (TFC) using the aluminum chloride colorimetric method. The isolate QS1 was identified as Bacillus pacificus through polyphasic characterization. Phytochemical screening of its crude extract confirmed the presence of flavonoids and terpenoids, while alkaloids, phenolics, tannins, saponins, and proteins were absent. Quantification revealed a high flavonoid yield of 18.62 mg Quercetin Equivalents (QE) per mL of crude extract. The endophytic bacterium Bacillus pacificus QS1, isolated from C. quadrangularis, is a prolific producer of flavonoids and terpenoids. This finding provides a novel microbiological perspective for the plant's documented osteotherapeutic and antioxidant activities, suggesting that its endophytic microbiome is a significant and sustainable source of bioactive compounds. This research underscores the potential of endophytic bacteria as alternative producers of valuable pharmaceuticals, reducing the reliance on direct plant extraction.