Phytochemical screening, free radical scavenging and antibacterial activity of <i>Cassia sieberiana</i> root bark extracts

Abstract

Cassia sieberiana is a tropical plant, widely distributed throughout Sudan and Guinea savannah. It is used in traditional medicine for the treatment of malarial, cancer and stomach ache. The study was conducted to screen for phytochemicals, free radical scavenging and antibacterial potentials of the root bark. It was extracted successively by Soxhlet extractor using n-hexane, dichloromethane and methanol. The phytochemical screening of the extracts revealed the presence of saponins, flavonoids, tannins, anthraquinones, phenolics, alkaloids, carbohydrates, steroids/triterpenoids and cardiac glycosides. Qualitatively screening for free radical scavenging compounds using 1,1-Diphenyl-2-PicrylHydrazyl (DPPH) was carried out on TLC. The result showed greater activity in the methanol extract. In vitro quantitative determination of free radical scavenging activity using DPPH at 2.5, 5, 10 and 20 mg/mL also showed methanol extract with highest activity (IC₅₀ of 0.25 mg/mL). The activity demonstrated may be due the presence of phenolic compounds. The dichloromethane and methanol extracts showed good antibacterial activity against S. aureus, B. subtilis, E. coli and P. aeruginosa. The zones of inhibition of growth produced by the dichloromethane and methanol extracts on the microorganisms at 15, 20, 25 and 30 mg/mL ranged from 2 - 20 mm. The MIC and MBC revealed that, dichloromethane and methanol extracts were both bateriostatic and bactericidal. Results obtained from this research have provided preliminary evidence for the use of C. sieberiana root bark in traditional medicine for treatment of diseases attributed to free radicals and microbial infections.

Keywords: Cassia sieberiana, DPPH, Antibacterial, Phytochemical, Phenolic Content