Preliminary phytochemical and antimicrobial screening of the calyx of green <i>Hibiscus sabdariffa</i> (Linn) (Malvaceae)

Abstract

Successive extraction of air-dried calyces of Hibiscus sabdariffa Linn (green roselle) in cold maceration using hexane, ethyl acetate and methanol gave the corresponding extracts. The phytochemical screening of these extracts revealed the presence of carbohydrates, tannins, phlobatannins, terpenes and sterols. Antimicrobial screening of the extracts showed activity in the ethyl acetate extract at 2000 μg/ml against all the test organisms namely: Esherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 29213), Pseudomonas aeroginosa (ATCC 27853) and clinical isolates of Salmonella typhi, Candida albicans and Bacillus subtilis. One of the ethyl acetate chromatographic fractions exhibited the most significant antimicrobial activity against Candida albicans at MIC of 16 μg/ml, while the other fractions gave MIC ranging between 250 μg/ml and 500 μg/ml against all the test organisms. The methanol extract showed activity against Escherichia coli and Candida albicans but only one of the fractions exhibited partial antimicrobial activity at 500 μg/ml. The hexane extract displayed no activity against all the test organisms. The minimum inhibitory concentration (MIC) of both the ethyl acetate and methanol extracts was 500 μg/ml against Esherichia coli. As a standard, chloramphenicol had an MIC of 50 μg/ml against five of the test organisms excluding Candida albicans. The results provide scientific justification and support for the ethnomedicinal use of the plant as a traditional remedy for camel sores, bleeding gum, respiratory tract infections and typhoid fever.

Keywords: Green Hibiscus sabdariffa, phytochemical constituents, antimicrobial activity