Evaluation Of Biological Activity Of Alkaloids And Flavanoids In Zanthoxylum Gilletii (De Wild Waterman) Extracts From Different Geographical Regions In Kenya

ABSTRACT

Plants appear to be almost an exclusive source of medicine to the worlds’ gradually increasing population with substances derived from them constituting a big percentage of all prescribed conventional medicines and other products. This puts pressure on the demand for medicinal plants, most of which are sourced from the wild. Zanthoxylum gilletii is an African indigenous deciduous tree which is overexploited for its medicinal use among many communities. This species has its habitat encroached and information on its alkaloids and flavanoids lacking. The objectives of this study were to determine antimicrobial and antioxidant activity of plant extracts and then identify alkaloids and flavanoids in the Kenyan Z. gilletii root, bark and leaf samples from different geographical regions. Antimicrobial activity tests were carried out using TLC bioautographic assays and ninety six well microtitre assays. Pathogens used during the tests were Saccharomyces cereveciae and Cladosporium herbarum as fungal pathogens; Bacillus subtilis and Pseudomonas syringae as the bacterial pathogens. Efficacy was confirmed by determining the minimum inhibitory concentration (MIC) and comparing against clinically used drugs, nystatin and chloramphenical as positive controls in antifungal and antibacterial assays respectively. Antioxidant activity was tested using the nitric oxide scavenging assay. Alkaloids and flavanoids were identified using HPLC and LCMS analysis methods. Plant extracts showed antimicrobial activity against both gram positive and gram negative bacteria while tests for antioxidant activity of the plant extracts were negative. Analysis of variance (ANOVA) revealed no significant difference between extracts from different plant parts and regions (P =0.05). Extracts contained a wide range of alkaloids and two flavanoids diosmin and hesperidin with compound profiles varying among plant parts and from the different geographical regions. Good antimicrobial activity was observed in the root extracts while the root extracts did not show any antimicrobial activity. Study revealed that the compound profiles relate with antimicrobial activity and that Z. gilletii is a poor antioxidant.