Phytochemical Screening, Atomic Absorption Spectroscopy, GC-MS and Antibacterial Activities of Turmeric (Curcuma longa L.) Rhizome Extracts

Abstract

Aim: The study evaluates the phytochemical screening, atomic absorption spectroscopy (AAS), Gas chromatography–mass spectrometry (GC-MS) and antibacterial activities of aqueous and methanolic extracts of turmeric (Curcuma longa) rhizome against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). 
 Place and Duration of Study: The study was carried out for six months in 2020 in Biochemistry
 Laboratory, Department of Chemical Sciences, College of Basic Sciences, Lagos State University of Science and Technology (LASUSTECH), Ikorodu, Lagos State, Nigeria.
 Methodology: The phytochemical screening, GC-MS and AAS were determined using standard methods. Antibacterial activities were evaluated by disc diffusion and agar well diffusion methods. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) were determined using standard procedures. 
 Results: The aqueous and methanolic extracts of turmeric (Curcuma longa) rhizome showed the presence of phytochemicals like tannins, flavonoids, alkaloids, reducing sugar and saponin. Mineral composition analysis shows that the plant contains Na, Ca, Mg, K and Fe. Nineteen compounds were identified using GC-MS analysis of turmeric with a R-Turmerone being the most abundant with peak area of 50.05%. The results revealed that at 250 and 500 mg/mL for both aqueous and methanolic root extract of C. longa were sensitive to both organism, with zone of inhibition of 22.29±2.35, 29.56±2.23, 21.79±1.04 and 29.95±1.83 against E. coli and 22.31±1.59, 28.67±1.42, 22.96±0.96 and 30.13±1.94mm against S. aureus respectively. Azithromycin has zone of inhibition values that ranges from 19.35±1.02 to 32.03±1.23 mm for both organisms tested at 12.50 and 25.00 mg/mL respectively. E. coli and S. aureus were susceptible to erythromycin, ciprofloxacin, roceplin, and streptomycin and resistant to chloramphenicol and septrin for only S. aureus. The MIC of the aqueous and methanolic root extract of turmeric on E. coli and S. aureus were 62.50, 31.25, 31.250 and 15.625 mg/mL while their MBC values were 250.00, 62.500, 62.500 and 31.2500 mg/ml respectively. MBC/MIC values show that both extracts had bactericidal effects. 
 Conclusions: Curcuma longa has essential minerals, phytochemicals, antibacterial activity and may prevent pathogenic diseases caused by Escherichia coli and Staphylococcus aureus.