Chemical Composition of the Stem Extract of Costus afer (Bush Cane) and Its Antimicrobial Activity

Aim: To determine the chemical composition of the stem extract of costus afer and its antimicrobial activity against some human and plant pathogens.

Study Design: The study was designed to identify the phytochemicals present in Costus afer and to test the inhibitory ability of the plant extract on human and plant pathogens.

Place and Duration of Study: Department of Chemistry, Alvan Ikoku Federal College of Education, Owerri and Department of Plant Science and Biotechnology, Imo State University, Owerri, Nigeria, between May to November 2015.

Methodology: The phytochemicals from the stem of Costus afer a medicinally important plant of the zingiberaceae family were extracted with ethanol and subjected to GC/MS analysis and the identification of compounds was done by comparing spectrum of the unknown component with the spectrum of the known components stored in the NIST library. The antibacterial activity was performed by filter paper disc diffusion technique. The antifungal activities of stem extract of Costus afer on mycelial growth evaluation the antifungal activities of stem extract of Costus afer along with mancozeb on mycelial growth inhibition of fungi isolated from Dioscorea rotundata (poir) (white yam) was also performed by disc diffusion technique.

Results: The analysis revealed that ethanolic extract of Costus afer contains ten compounds with n- Hexadecanoic acid forming the bulk of the oil (27.35%), followed by 4–methyl-4-hepten– 3-one (24.27%), Oleic acid (18.79%), Stearic acid (10.27%), 3,5-Dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (8.46%). Other compounds present were Furfural (2.46%), 6-Methyl-3(2H)- Pyridazinone (1.75%), etc. The ethanol extract inhibited all the tested organisms S. aureus, P. mirabilis, K. pneumonia, P. aeruginosa and E.coli. The results revealed that Costus afer inhibited the growth of the test organisms Aspergillus niger, Fusarium oxysporium and Botryodiploidia theobromae except Rhizopus stolonifer. In vivo results showed that C. afer extract was effective in reducing tuber rot which suggested that use of C. afer would be helpful in treatment of mycotic infections and in the control of fungal plant disease justifying the use of this plant in the treatment of both human and plant diseases.