In this, four formulations of Neolamarckia cadamba with Butea monosperma, Citrus sinensis, Hibiscus rosa-sinensis, and Spinacia oleracea were evaluated for synergy, on the basis of antioxidant activity by in-vitro testing using DPPH Method, Nitric oxide radical scavenging assay method and Phosphomolybdenum method. Synergy in antioxidant activity of all four formulations was supported by enhancement of the flavonoid and total phenolic content as compared to their values for the single plant(s) drugs. HPTLC study revealed that there was an enhancement of area under the peak for a few R_f values in the formulations that exhibited synergy in their radical scavenging activity. Combination Index values for the formulations were found to be indicative of synergism. The formulations thus offer can desirable pharmacological action with a lower dose with the same or better therapeutic effect.