Phytochemical Testing and In vitro Antibacterial Activity of Bixa orellana (Annatto) Seed Extract

Aim: The present study was designed to investigate the antibacterial activity of the seeds of Bixa orellana(Annatto, family Bixaceae) extracts.
Methods: Powdered seed material was extracted using either organic solvents or acid-base protocols and the crystals obtained were washed with deionized water, oven-dried for about 12 hours at 45ºC and stored inair-tight containers. The antimicrobial activity of the ethanolic, dimethyl sulphoxide and aqueous extract of B. orellana seed was tested In vitro against Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Bacillus subtilis using agar well diffusion method.
Results: The antibacterial activity of the seed extract was observed at low concentration (250µg/ml) in ethanolic and dimethyl sulphoxide solution while, in potassium hydroxide, antibacterial activity against Staphylococcus aureus and Bacillus subtilis was observed at 750µg/ml. The minimum inhibitory concentration (MIC) values range from75 to 750µg/ml while the minimum bactericidal concentration (MBC) values occurred between 75 and 1500µg/ml respectively against Staph. aureus and B. subtilis respectively.
Conclusion: Results of this study indicated that the seed extracts of Bixa orellana possess significant inhibitory and bactericidal activities against select resistant strains of gram-positive bacteria.