Objective: The aim of the present study was designed for the induction of callus from leaf explants of Decalepis arayalpathra (D. arayalpathra) and to analyse their phytochemical constituents and antibacterial activity.Methods: The explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentration of 2, 4-dichlorophenoxyacetic acid (2, 4-D) and later subcultured to the combination of 6-benzylaminopurine (BAP) and 1-naphthaleneacetic acid (NAA). The phytochemical constituents were analysed in the different solvent extracts using standard methods. Antibacterial activity of the different solvent extracts was carried out using agar well diffusion method against reference standards. Results: Callus induction was observed on MS medium supplemented with different concentration and combination of auxins and cytokinins. Maximum callus induction was noticed on media supplemented with 2, 4-D (2 mg/l) and BAP (1 mg/l)+NAA (0.5 mg/l) respectively. The phytochemical screening revealed the presence of alkaloids, flavonoids, phenols, tannins, steroids and terpenoids, glycosides, coumarins and quinone etc. All the solvent extracts showed varying degree of antibacterial activities against the bacterial strains (Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas fluorescence and Staphylococcus aureus). The maximum antibacterial activity of leaf was observed in aqueous (Klebsiella pneumoniae, 19.00±1.00) and methanolic extract (Klebsiella pneumoniae, 18.33±1.15). Whereas petroleum ether extract of the callus showed maximum inhibition (Bacillus subtilis, 17.00±1.00) compare to other extracts.Conclusion: The study revealed the presence of secondary metabolites in the leaf and callus extracts of D. arayalpathra. The methanolic extracts possess higher antibacterial activity compared to other solvent extracts. However, further studies have to be carried out for the isolation and identification of antimicrobial compounds against pathogens
