Antimicrobial and Larvicidal Efficacy of the Methanolic Extract of Spinifex littoreus (Burm F.) Merr.

ABSTRACT: The increasing drug resistance of microbial populations is driving researchers to discover novel antimicrobial agents. Plants are the major reservoir of secondary metabolites which are capable of fighting against microorganisms. The current study focused on identifying a potent antimicrobial and larvicidal agent from the coastal plant Spinifex littoreus (Burm f.) Merr. The leaves of S. littoreus were extracted with methanol and used for further analysis. The antimicrobial assay of the methanolic extract of S. littoreus (SL-M) was conducted by agar well diffusion method for 6 bacterial (Escherichia coli, Propionibacterium acnes, Staphylococcus aureus, Aeromonas hydrophila, Streptococcus faecalis, Bacteroids fragilis) and 4 fungal (Cryptococcus neoformans, Aspergillus fumigatus, Aspergillus niger, Sporothrix schenckii) strains. Nutrient agar and Potato dextrose agar medium were used respectively, and different SL-M extracts were introduced. After incubation, the zone of inhibition was calculated. As for the larvicidal bioassay, the larvae of Aedes aegypti were grown in distilled water and they were treated with different concentrations of SL-M extracts. After 24 hours of incubation, larval mortality rate and LC50 values were calculated. The antimicrobial assay revealed that P. acnes and C. neoformans showed maximum inhibition than the other tested strains. The SL-M extract showed dose-dependent activity against larvae of Ae. aegypti. And the predicted LC50 value is 67.058 ppm. Considering the results of this current research the methanolic extract of S. littoreus can be an alternative source of antibiotics as well as a potent mosquito larval repellent.