Analysis of anthraquinone contents and antimicrobial evaluation of the pods of Senna alata (Linn.) Roxb. and Senna podocarpa (Guill. & Perr.) Lock. (Fabaceae)
Senna alata and Senna podocarpa are two medicinal plants that have long been used as laxative and treatment of skin diseases. The pods have not been investigated for antimicrobial activity. This study was aimed at evaluating the antimicrobial properties and analysis of the anthraquinone contents of the pods. The antimicrobial activity of the ethanolic extract of the two Senna species pods were evaluated by agar diffusion method using these organisms: bacteria –Bacillus subtilis, Escherichia coli and Staphylococcus aureus; and fungi –Aspergillus niger, Candida albicans and Trichophyton rubrum. The ethanolic extract of S. alata exhibited antibacterial activity against B. subtilis - zone of inhibition at 250mg/ml was 19mm while the zones of inhibition for S. podocarpa against B. subtilis and E. coli at 125mg/ml was 17mm and 20mm respectively. The two Senna species inhibited only one fungus, T. rubrum - the zone of inhibition at 125mg/ml was 14mm for S. alata and 23mm for S. podocarpa. The thin layer chromatography (TLC) analysis of the anthraquinone contents of the Senna species pods using solvent system – Benzene: ethyl acetate: glacial acetic acid (7:2:1) and aluminum coated silica gel plates showed the presence of both free and combined anthraquinone while UV analysis showed that the percentage of combined anthraquinone for S. alata was 0.004% w/w and 0.0303% w/w for S. podocarpa. Official Senna pod used as standard had a value of 0.133% w/w.
Key words: Senna alata, Senna podocarpa, antimicrobial activity, anthraquinone contents