Investigation of phytoconstituents and antimicrobial evaluation of Acacia mangium leaves extract / Mohd Faqhrull Shafiq Abd Kadir

Acacia mangium is one of the most abundant plant in Malaysia since its introduction as a main source of wood and pulp for the wood industry. With the increasing trend of multi-drug resistance microbes and increasing cost for a mean to fight these microbes, a highly available and sustainable source of antimicrobial agent is required. This study focuses on determining the potential of Acacia mangium leaves as a source of antimicrobial agent by achieving several objectives including detecting the phytoconstituents of leaves extract, antimicrobial assay against gram-negative bacteria, gram-positive bacteria and a fungus and followed by determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against tested organisms. The methods used were extraction of Acacia mangium leaves in 50% methanol and 50% acetone followed by phytochemical screening to detect the presence of compounds that has a potential as antimicrobial agents, disc diffusion assay of both solvents leaves extract and the determination of MIC and MBC. The results presented that 50% methanol and 50% acetone leaves extract showed the presence of phenol, tannins, flavonoids, terpenoids and alkaloids while reducing sugar was absence in both solvent leaves extract. Saponin were only detected in 50% methanol leaves extract while protein and quinones were only detected in 50% acetone leaves extract. The antimicrobial activity of both solvent plant leaves extract were further evaluated against gram-negative bacteria, gram-positive bacteria and a fungus that showed only Acacia mangium 50% acetone leaves extract exhibit moderate antimicrobial activity against S. aureus at 12.33 ± 1.15 mm while both solvents extract showed no antifungal activity against C. albicans. Antibacterial activity against S. aureus, E. coli and P. aeruginosa is considered as weak. The MIC and MBC for 50% methanol leaves extract against S., E. coli and P. aeruginosa was determined to be 15,630 pg/ml, 7,810 pg/ml and 31,250 pg/ml respectively. For 50% acetone extract, the MIC and MBC for S. aureus, E. coli and P. aeruginosa was determined to be 3,900 pg/ml, 3,900 pg/ml and 15,630 pg/ml respectively while for S. agalactiae the MIC and MBC was 62,500 pg/ml and 125,000 pg/ml respectively. Acacia mangium 50% methanol and 50% acetone leaves extract shown no antifungal activity against a weak fungus C. albicans and showed an overall weak antibacterial activity against gram-negative and gram-positive bacteria. Recommendation for future research of Acacia mangium would be to diversify solvent used for extraction, antibiotic disc against test organisms and quantification assay of secondary metabolites detected in the extract.