Protectant, insecticidal and antimicrobial potentials of Dalbergia saxatilis Hook f. (fabaceae)

The protectant, insecticidal and antimicrobial potentials of the Nigerian plant, Dalbergia saxatilis (Fabaceae) were investigated. The dried powdered leaves of D. saxatilis were established as a control agent for the cowpea pest, Callosobruchus maculatus. Damage was drastically reduced when cowpea seeds were treated with dry powdered leaves of D. saxatilis. Doses of 0.75 g/150 seeds and above significantly reduced crop damage, oviposition and larval development without affecting the viability of the seeds. Similarly, the crude 95% ethanol extract and the aqueous methanol and hexane fractions of the bark extract showed insecticidal activity against adult mosquitoes at 0.2% concentration in ethyl acetate. The crude 95% ethanol extracts of the leaves and bark were screened against six pathogenic microorganisms (ATCC). While the leaves extract was active against only Staphylococcus aureus at minimum inhibition concentration (MIC) 1000 mg/ml, the bark extract displayed broad and interesting antimicrobial spectra. The bark extracts gave activity at MICs 250, 125, 1000 and 1000 mg/ml against S. aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa, respectively. The above properties demonstrate the great potentials of D. saxatilis for use in agriculture and medicine. The relevance of bioassay-guided fractionation in ensuring consistency and enhancement of efficacy and quality of phyto-medicines and bio-pesticides is discussed.