Phytochemical constituents and antioxidant activity of critically endangered <i>Ophiorrhiza radicans</i> Gardn. (Rubiaceae: Ophiorrhizeae) from Southern Western Ghats, Kerala, India

The present study provides a novel report on the phytochemicals and antioxidant potential of <i>Ophiorrhiza radicans</i> whole plant. Both primary and secondary metabolites were identified in hexane, ethyl acetate, ethanol and defatted ethanol extracts. Proximate analysis estimated the moisture content (65.46 ± 0.277%), carbohydrate (3.432 ± 0.035 mg/g), crude fat (82 ± 1.32%), free amino acid (4.97 ± 0.055 mg/g) and protein (18.16 ± 0.109 mg/g) content of <i>O. radicans</i>. Total alkaloids, phenolics, flavonoids and steroid content of ethyl acetate, ethanol and defatted ethanol were also determined. The defatted ethanol extract was rich in secondary metabolites compared to other extracts, with high alkaloid content (130 ± 1.37 mg/g), followed by phenolics (11.99 ± 0.03mg/g), flavonoids (11.91 ± 0.02 mg/g), and steroids (8.25 ± 0.032 mg/g). HPLC analysis confirmed the presence of gallic acid and camptothecin, marking the first report of these compounds in this taxon. The IC₅₀ value for ethanolic extract by DPPH assay was 12.93 µg/ml highlighting <i>O. radicans</i> as a promising natural antioxidant.