Comparative Study of Biological Activities of Methanolic Extracts from Two Medicinal Plants Cinnamomum zeylanicum (Cinnamon) and Zingiber officinale Roscoe (Ginger)

Abstract

This study aimed at extracting and quantifying phenolic compounds from Cinnamomum zeylanicumand Zingiber officinale Roscoe, then subjecting them, in vitro, to screening based on their richness in polyphenols, flavonoids, and their antioxidant potential. The extraction of phenolic compounds was performed by maceration in absolute methanol. The quantification of polyphenols and flavonoids from two extracts was performed using colorimetric techniques; the Folin-Ciocalteu reagent and the aluminum trichloride. The evaluation of the antioxidant activity was performed by three methods: FRAP, DPPH-radical scavenging, and H2O2 neutralization. Lipid peroxidation was evaluated by thiobarbituric acid reactive substances. In addition, the antibacterial activity, using the agar diffusion and incorporation methods, was tested on four bacteria (Escherichia coli ATCC 2592, Pseudomonas aeruginosa ATCC 27853, Bacillus cereus ATCC 11778, and Staphylococcus aureus ATCC 33862). The results showed that the methanolic extract from Cinnamomum zeylanicum (MEC) was richer in polyphenols than the methanolic extract of Zingiber officinale Roscoe (MEG). A strong antioxidant capacity was observed and highly significant with MEC compared to MEG for the three techniques used, the FRAP test (EC50 = 108.56 ± 4.18 µg/ml versus 310.07 ± 6.94 µg/ml respectively). The IC50 of DPPH-radical (5.27 ± 0.11 µg/ml versus 22.50 ± 0.45 µg/ml). Therefore, a highly significant inhibition potential of lipid peroxidation was obtained withMEC compared to MEG with MDA levels (57.68 ± 1.64 and 63.02 ± 2.95 µmol/g tissue), respectively. EMC has a strong antibacterial effect against Gram-positive and Gram-negative bacteria. Cinnamon exerts powerful biological activities compared to ginger; this ability could be due to the high content of phenolic compounds in the bark.