Antioxidant and antibacterial activities of hibiscus (Hibiscus rosa-sinensis L.) and Cassia (Senna bicapsularis L.) flower extracts

Antioxidant activity, antibacterial properties, color and ft-ir spectral analysis of flowers belonging to hibiscus and cassia species were investigated. radical scavenging activity of sample extracts were determined based on the percent inhibition of dpph and ferric reducing antioxidant power (frap) assays. total phenolics were estimated based on the folin–ciocalteu method, while, vanillin–hcl and aluminum chloride methods were employed to estimate total tannins and flavonoids in the sample extracts, respectively. to determine total flavonols and anthocyanin contents, spectrophotometric method was employed. for antibacterial activities, modified agar disk diffusion method was adopted. color analysis was performed using a colorimeter, while functional groups of compounds were identified using a ftir-spectrophotometer. results showed both the flower extracts to encompass high amount of antioxidant compounds and exhibit significant antioxidant activities, which depended on extraction solvents. ethanolic extracts of cassia had high total phenolic, total flavonoid and total flavonol content, and showed highest activity for inhibition of dpph, while aqueous extract of hibiscus had high tannin and anthocyanin contents, and showed high ferric reducing antioxidant power. with regard to antimicrobial activity, aqueous and ethanolic extracts of hibiscus inhibited the growth of food-borne pathogens such as salmonella typhimurium and staphylococcus aureus, while in cassia the growth of bacillus cereus and klebsiella pneumoniae was inhibited. compared to cassia, color analysis of hibiscus showed lower chroma and hue angle values. ftir spectra of both flowers were comparable and showed the presence of polysaccharides, suberin and triglycerides. our results indicate the potential of exploiting these two flowers as a source of natural food preservative or colorant, while developing novel functional foods.