The present study was undertaken to evaluate in vitro antioxidant activity of methanolic extract from leaves of four plants viz. Clerodendron colebrookianum Walp. (Verbinaceae), Gnetum gnemon L. (Gnetaceae), Sarcochlamys pulcherrima (Roxb.) Gaud. (Urticaceae), Garcinia lancifolia (Don) Roxb. (Cluciaceae), from Cachar district, Assam, India. DPPH (1,1-diphenyl 2-picrylhydrazyl) radical scavenging capacity, reducing power assay (RPA) and photochemiluminescence (PCL) assay were used for evaluating in vitro antioxidant activity. Total phenolic content (TPC) was estimated by Folin–Ciocalteu’s method. Sarcochlamys pulcherrima showed highest antioxidant activity (DPPH EC50 9.70 ±1.51ppm), as compared to C. colebrookianum (121.05 ±1.09ppm), G. gnemon (255.99 ±0.82ppm), and G. lancifolia (344.96 ±0.76ppm). Highest activity of S. pulcherrima was also supported by RPA and PCL and highest TPC (0.33 mg gallic acid equivalent/mg of dry extract) amongst the plants, indicated that phenolic compound are mainly responsible for the activity.