10.22376/ijpbs.2019.10.1.p1-12 Volume 8 Issue 4 2017 (October - December) Unripe and ripe pericarp extracts of lessThan i greaterThan Annona reticulata lessThan /i greaterThan Linn. fruits were investigated for their lessThan i greaterThan in vitro lessThan /i greaterThan antimicrobial properties against three gram-positive bacteria ( lessThan i greaterThan Bacillus subtilis lessThan /i greaterThan , lessThan i greaterThan Enterococcus faecalis lessThan /i greaterThan and lessThan i greaterThan Staphylococcus aureus lessThan /i greaterThan ), gram-negative bacteria ( lessThan i greaterThan Eschericia coli lessThan /i greaterThan , lessThan i greaterThan Pseudomonas aeruginosa lessThan /i greaterThan and lessThan i greaterThan Proteus vulgaris lessThan /i greaterThan ) and three fungal strains ( lessThan i greaterThan Aspergillus flavus lessThan /i greaterThan , lessThan i greaterThan Aspergillus niger lessThan /i greaterThan and lessThan i greaterThan Penicillium chrysogenum lessThan /i greaterThan ). All the extracts showed activity against at least one strain of bacteria and fungi and the result shows there is significant differences (P lessThan 0.05) between the activities of extract on microorganism. The ethanol extract of unripe pericarp exhibited the highest inhibition activity against the growth of lessThan i greaterThan Eschericia coli lessThan /i greaterThan (19.67 mm) which was higher than the zone of inhibition produced by Ampicillin standard (15.33 mm). Also MIC for ethanol extract was the lowest (1.0 mg/ml) compared with other extracts. From the investigation carried out it was seen that the ethanolic extract of unripe pericarp could be a possible source of obtaining new and effective herbal medicines to treat infections. V.S.SANGEETHA , BEENA LAWRENCE antimicrobial activity, disc diffusion method, MIC, Inhibition zone 169-177