Taxonomical, Chemical Characterization and Biological Activity of Cassia and Senna Species

Abstract

Several species within the genera Cassia or Senna have a treasure of traditional medicines worldwide. The objective of the present study was to study the morphological characteristics of C. fistula, C. grandis, S. alexandrina and S. italic and evaluate, in vitro, antimicrobial and antioxidant activities of their crude leaf extracts. In addition, phytochemical screening of secondary metabolites and the total polyphenolic, flavonoids and tannins contents of these extracts were determined. Extracts from each plant were prepared by sequential maceration of dried leaf powder in solvents of increasing polarity. The antimicrobial activity was evaluated against Gram positive and Gram negative as well as two fungi by disc diffusion method. Antioxidant activity was assessed based on the scavenging activity of the stable 2,2-Diphenyl- 1-picrylhydrazyl free radical. Phytochemical screening was performed by thin layer chromatography technique. Total polyphenolic, flavonoids and tannins contents were determined by spectrophotometric methods. Taxonomically the Cassia spp. and Senna spp were separated from each other by the filaments form and the presence or absence of bracteoles. Results of antimicrobial activity showed that extracts of the four plants exhibited better antifungal activity than antibacterial one with highest antifungal activity against C. albicans (28 mm) and A. niger (27 mm) was recorded from the ethyl acetate extract of C. fistula. The highest antibacterial activity against Staphylococcus aureus (18 mm) and Pseudomonas aeruginosa (18 mm) was exerted by the methanolic extract of C. grandis and chloroform extract of S. alexandrina respectively. Bacillus subtiles and Escherichia coli were less sensitive to all tested extracts. The highest radical scavenging activity was obtained from the ethyl acetate extract of C. fistula (77%) and two polar extracts of C. grandis (71%). Phytochemical screening showed that extracts were mainly rich in phenolic compounds. Total polyphenolic were mainly accumulated in the

ethyl acetate (136.8 – 277 mg gallic acid equivalent (GAE)/g) and methanolic (20.8 - 108.8 mg GAE/g) extracts while the majority of extracts had higher flavonoids content (17.66 - 618.66 mg quercetin equivalent/g) than their respective polyphenolic content. All extracts except methanolic extract of C. grandis and S. alexandrina were devoid of tannins. In conclusion, these plants could be a very beneficial source of natural bioactive agents.