Phytochemical and Antimicrobial Screening of the Stem Bark Extract(s) of Indigofera Arrecta Hochst EX A. Rich (Fabaceae)
The Pulverized stem bark of Indigofera arrecta was exhaustively extracted with methanol and concentrated in vacuo using rotary evaporator at 40 0C.The extract was later subjected to solvent partitioning to yield soluble extracts of n-hexane, ethyl acetate, chloroform, and methanol. Genernal phytochemical screening of the fractions revealed the presence of secondary metabolites such as cardiac glycoside,steroid, terpenes flavonoids and tannins. The antimicrobial activity against S. aureus,S. pyogenes,S.feacalis, S.typhii, E.coli C. ulcerans,P. vulgaris and C.albicans was tested using the tube dilution and agar diffusion methods as outlined by the NCCLS. The results of the antimicrobial activity as indicated by the zonesof inhibition of growth of microorganism ranged from 20mm to 40mm for the n-hexane extract, 16mm to 21mm for ethyl acetate extract and 20mm to 27mm for the methanol extract. The MIC result for the n-hexane, ethyl acetate and methanol extracts ranged from 7.5mg/ml to 15mg/ml. The MIC of 15mg/ml exhibited by the n-hexane extract against both gram positive and gram negative bacteria indicates broad spectrum activity of Indigofera arrect. The n-hexane fractions was subjected to Column Chromatography using silica gel to yield 87 fractions, which were combined based on their thin layer chromatography analysis and recrystallized in methanol to give a pure white crystalline powder, which melts at 144oC. The structure of the isolated compound was established by spectroscopic analysis and by direct comparison of the data obtained with those reported in literature to be Stigmasterol (3β,22E-Sigmasta-5,22-dien-3-ol).
Definition of a drug
A drug can be described as any chemical substance that has no nutritional value when introduced into the body but causes some physiological effects within the system (Mbah, 2000). Drugs are classified under pharmaceuticals. Pharmaceutical drug, according to Dey (2006), also refers to as medicine or medicament, can be loosely defined as any substance intended for use in the diagnosis, cure, mitigation, treatment or prevention of diseases.
Some pharmaceuticals occur naturally in plants. These can be called phyto pharmaceuticals. By the strictest definition, they are drugs or chemicals that may have health related effects but are not considered essential nutrients. Protein, carbohydrates, fats, minerals and vitamins are regarded as essential nutrients. Some pharmaceuticals found in plants include gedunin and nimbolide from Azadirachta indica (Neem) (Khalid and Duddeck, 1993); santonin, a sesquiterpenoid lactone is found in species of Artemisia which grows in Asia, quinine and alkaloid occurs in the bark of cinchona tree; penincillin- a beta-lactam is produced by fungi in the genus Penicillium (Finar, 2003) and reserpine-an alkaloid is isolated from Rauwolfia plant.
1.2 Medicinal plants
According to biblical records, Prophet Ezekiel reported that the fruits will serve as food and their leaves for healing (Ezekiel 47:12). Thus, the use of plants for medicinal purposes dates back to thousands of years ago as the earliest humans used various plants to treat illness.