Phytochemical Screening, Antimicrobial Activity and Acute Toxicity of Aloe Turkanensis
The use of plants to cure diseases and relieve physical sufferings started from the earliest times of mankind’s history. Due to antimicrobial resistance becoming a global problem with far reaching implications for the survival of human race, efforts are continuously made to overcome this. Current efforts include research in finding new and safe antimicrobials from plants. Among these plants is Aloe turkanensis which is a widely used medicinal shrub in Kenya. The plant grows naturally in Turkana and West Pokot counties where it is used in ethnomedicine and ethinoveterinary medicine. It is also cultivated in Baringo, Isiolo, Laikipia counties and natural resource conservatory institutes. Traditional Medical Practitioners (TMPs) in Turkana County uses herbal preparation of the plant to manage various ailments despite lack of proper scientific evidence on efficacy, safety and sustainability of the plant. In this study, in-vitro antimicrobial, phytochemical and toxicity profile of a naturally growing and cultivated Aloe turkanensis plant was determined. This was done in order to find out whether the plant has the presumed bioactivity and also to explore the possibility of conservation through cultivation in other ecological zones which would help in meeting the demand of the consumers incase the hypothesis was true. An ethno botanical study on the use of Aloe turkanensis was done in Turkana County where qualitative data was collected through observation, photographing and questionnaires. A sample of the naturally growing whole xvii plant was harvested in Natira sublocation, in Turkana County in February 2012 after identification by Aloe-working group herbalists who voluntarily provided information on its medicinal uses. Botanical identification was done at Kenya Forest Service Research Centre in Karura where a voucher specimen was deposited. A cultivated species of A. turkanensis was harvested at Karura forest courtesy of the Kenya Forest Service Research Center. The naturally growing and cultivated plants ecotypes were treated independently where cold maceration using 70% methanol and distilled water was used for extraction. Bioassays to determine the effects of the extracts from the two plants ecotypes on brine shrimp and selected bacterial and fungal cultures were done. The extracts were tested for in-vitro activity against standard cultures of Bacillus cereus (ATCC 11778), Staphylococcus aureus (ATCC25923), Pseudomonas. aeroginosa (ATCC 27853), Escherichia coli (ATCC 25922) and a human infection clinical isolate of Candida albicans. The data from laboratory experiments was analyzed using descriptive statistics and analysis of variance (ANOVA) and it was found that methanol extracts of naturally growing Aloe turkanensis plant inhibited the growth of B. cereus (100 mg/ml), S. aureus (100 mg/ml), and P. aeroginosa (200 mg/ml) with mean diameters of inhibition zones for S. aureus and B. cereus being 18.5±0.7 mm and 16.5±0.7 mm, respectively. Aqueous extract of naturally growing A. turkanensis inhibited the growth of B. cereus and S. aureus at a Minimum Inhibitory Concentration of 200 mg/ml and 50 mg/ml respectively with mean xviii diameter of inhibition zones for S. aureus and B. cereus being 19.75±1.0 mm and 11.5±0.0 mm respectively. Methanol extracts of cultivated A. turkanensis plant inhibited the growth B. cereus (100 mg/ml), S. aureus (50 mg/ml), E. coli (400 mg/ml) and P. aeroginosa (200 mg/ml) with mean diameters of inhibition zones for S. aureus and B. cereus being 18.5±0.7 mm and 11.5±0.0 mm respectively. On analysis of variance, it was noted that there was a significant difference in antibacterial activity between the naturally occurring plant and the cultivated one (p<0.05) Phytochemical screening showed the presence of alkaloids, terpenoids, steroids, quinones, saponins and tannins in the plant extracts. The extract was found to be non-toxic at a concentration of 1000 μg/ml with a 100% survival of Brine Shrimp larvae. The results of this study show that methanol and aqueous extracts of A. turkanensis growing naturally in the study areas had more phytochemicals compared to a cultivated plant. These phytochemicals inhibit the growth of bacteria making it an effective ethnomedicine when administered at appropriate doses. However, there is need for further studies to validate the in-vivo bioactivity of the plant and generate adequate toxicological data to support its ethno medicinal use, conservation, value chain of its products and its widespread use as herbal remedy.