Phytochemical analysis and antimicrobial activity of aqueous and methanolic extracts of the flowers of Nelumbium speciosum

Abstract

In present investigation aqueous and methanolic extracts of Nelumbium speciosum flowers were screened for phytochemical constituents and antibacterial activity to ascertain their traditional use. Antimicrobial activity of both extracts was tested by Kirby-Bauer disc diffusion method against four Gram positive strains, viz. Staphylococcus aureus (ATCC25923), Streptococcus agalactiae (13813), Bacillus subtilis (ATCC 6633), Staphylococcus epidermidis (ATCC 12228) and four Gram negative bacterial strains Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (ATCC 27853), Proteus mirabilis (12453) and Klebsiella pneumoniae (10031). Phytochemical analysis showed the presence of tannins, saponins and alkaloids in both extracts while flavonoids and steroids were present only in methanolic extract. Methanolic extract of Nelumbium speciosum flower showed concentration dependent antibacterial activity against all tested strains with maximum zone of inhibition (17.3±0.3mm) against P. aeruginosa. Aqueous extract showed concentration dependent activity against S. aureus, E. coli, B. subtilis and S. epidermidis with maximum antibacterial activity against E. coli (14.3±0.3mm). MIC of methanolic and aqueous extracts was in the range of 0.015-0.251 and 0.0625-0.251 mg/mL, respectively. Results showed that methanolic extract of Nelumbium speciosum exhibits superior antibacterial activity than aqueous extract.