The increasing rate of resistance to antibiotics and insecticides by microorganisms and various insect pests have become an issue of Public Health concern. In this research, various concentrations of extracts were tried against three Gram negative isolates, zones of inhibitions were recorded in (mm) after 24hrs. Fourth (4th) instar larvae of A. gambiae were tested against various extract concentrations, and mortality recorded over 72hours. Results obtained showed that both methanolic and aqueous extract of seed samples showed excellent antimicrobial activity against the isolates tested. The aqueous extract showed more activity against both E. coli and E. aerogenes, however Klebsiella spp were more susceptible to the methanolic extract. The Minimum Inhibitory Concentration (MIC) values of isolates determined usingbroth dilution method reveals that the MIC of the methanolic Extracts were ≤20mg/ml, ≤30mg/ml and ≤10mg/ml for E. coli, E. aerogenes and K. pneumonia respectively. MIC values of the aqueous extracts were found to be ≤30mg/ml, ≤20mg/ml and ≤30mg/ml for E. coli, E. aerogenes and K. pneumonia respectively. Result of larvicidal assay revealed that the methanolic seed extract of P. nitida showed a remarkable activity against the insect larva with a mean mortality of 18.7 ± 1.5, 19.3 ± 1.2 and 19.7 ± 0.6 for extract concentrations of 0.5mg/ml, 1.0mg/ml and 2.0mg/ml respectively after 24hours exposure. However, aqueous extract had mean mortalities of 4.7 ± 1.2 and 6.3 ± 1.2 at concentrations of 4.0mg/ml and 5.0 mg/ml after 72hours exposure time. LT95 values of methanolic seed extract at (P ≤ 0.05) was found to be 29 hrs and 16 hrs at concentrations of 0.5mg/ml and 1.0mg/ml, while LT95 value for aqueous extract at (P ≤ 0.05) was 489 hrs at 1.0mg/ml. This research shows that seed extracts of P. nitida are both efficient antimicrobials and larvicidal agents and its potential can be harnessed for future use.
Keywords: Antimicrobial, Larvicidal, Picralima Nitida, Seed Extracts
