SCREENING OF Gmelina arborea (Yemane) LEAF EXTRACTS FOR ANTIMICROBIAL, PHYTOCHEMICAL AND PESTICIDAL PROPERTIES

Abstract

Leaves of Gmelinaarborea were extracted using ethanol, methanol, and distilled water. Preliminary phytochemical screening of the extract revealed the presence of fats and oils, hydrolysable tannins, 2 deoxysugars, saponins and tannins. The agar disc diffusion method was used to determine the antibacterial and antifungal activity on three Gram (+) bacteria B. cereus, B. subtilis, and S. aureus ), two Gram (--) bacteria E. coli and S. typhi) and a fungus ( C. albicans). The highest activity was shown by the aqueous extract with a mean diameter of inhibition zone ranged from 15.33 24.67 mm followed by ethanol which had 14 23.67 mm and lastly was observed in methanol which had 14 22.33 mm. The minimum
inhibitory concentration (MIC) of the extracts for E. coli, S. typhi and C. albicans was 56 mg/mL, for B. cereus, B. subtilis, and S. aureus ranged from 14 mg/mL 28 mg/mL. Pesticidal activity screening was determined using a Brassica juncea (mustasa) and lethal dosage was assessed using sawfly (Athalia lugens proxima). Lethal dosage was carried out using four concentrations (70%, 80%, 90% and 100%) for each of the extracts, which involved the determination of time of paralysis and time of death of the worm. The best activity was found in aqueous extract having 90% mortality rate in just 18 seconds, followed by ethanol and methanol both having 80% mortality rate in 25 and 29 seconds respectively. These promising findings suggest the presence of antibacterial and antifungal agents in the tested plant material, exhibited by its bioactive compounds, and serving them as an alternative antimicrobial agent against the tested microorganisms, furthermore, alcoholic and aqueous extract significantly demonstrated death of sawfly especially at higher concentration of the extract making this plant a potential agent as an organic pesticide.