Objective:To explore the in vitro antimicrobial potential of Holigarna arnottiana(H.arnottiana)against human and shrimp pathogenic bacteria and use GC-MS analysis to elucidate its antimicrobial principles.Methods:In the present study,organic extract of H.arnottiana was examined for in vitro antimicrobial potency against five clinical human pathogens,seven species of human type culture pathogens,six pathogenic Vibrio strains isolated from moribund tiger shrimp(Penaeus monodon)and seven type cultures(Microbial Type Culture Collection,MTCC)of prominent shrimp pathogens.Results:The extraction of H.arnottiana with ethyl acetate yielded bioactive crude extract that efficiently repressed the growth of all tested pathogens.Among the pathogens tested,shrimp pathogens were the most susceptible organisms while clinical pathogens were found to be a little resistant.The chemical constituents of the H.arnottiana were analysed by GC-MS which revealed the presence of major compounds such as 3,7.1 l,15-tetramethyl-2-hexadecen-l-ol(42.1%),l-lodo-2-methylundecane(34.4%)and squalene(11.1%)which might have a functional role in the chemical defence against microbial invasion.Conclusions:Based on the finding it could be inferred that H.arnottiana would be a reliable source for developing shrimp and human bio-therapeutics in future. Objective: To explore the in vitro antimicrobial potential of Holigarna arnottiana (H.arnottiana) against human and shrimp pathogenic bacteria and use GC-MS analysis to elucidate its antimicrobial principles. Methods: In the present study, organic extract of H.arnottiana was for in vitro antimicrobial potency against five clinical human pathogens, seven species of human type culture pathogens, six pathogenic Vibrio strains isolated from moribund tiger shrimp (Penaeus monodon) and seven type cultures (Microbial Type Culture Collection, MTCC) of prominent shrimp pathogens. Results : The extraction of H.arnottiana with ethyl acetate yielded bioactive crude extract that highly repressed the growth of all tested pathogens. Among the pathogens tested, shrimp pathogens were the most susceptible organisms while clinical pathogens were found to be a least resistant. The chemical constituents of the H.arnottiana were analysed by GC-MS which revealed the presence of major compounds such as 3, 7.1 l, 15 which might have a functional role in the chemical defense against microbial invasion. Conclusions: Based on (42.1%), l-lodo-2-methylundecane (34.4%) and squalene the finding it could be inferred that H.arnottiana would be a reliable source for developing shrimp and human bio-therapeutics in future.