Monitoring drought and effects on vegetation in Sokoto state, Nigeria using statistical and geospatial techniques

This paper aimed at assessing drought occurrences and its effects on vegetation cover in Sokoto State, Nigeria using geospatial and statistical techniques. Monthly precipitation data which span through a period of 40 years (1980-2010) and 30 years (1982-2011) respectively were used for generating Standardized Precipitation Index (SPI) graphs and maps. LandSat   imageries of bands 3 and 4 acquired by Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) Sensor were used for generating Normalized Difference Vegetation Index (NDVI). SPI and NDVI were generated for the study area based on inter-annual and decadal timescale. Findings showed that SPI values varied from extremely dry condition to extreme wet condition although near normal condition ranked highest while extremely wet condition ranked least.  It also revealed that most of the Local Government Areas experienced near normal conditions but  Isa, Sabon Birni and little part of the boundary between Goronyo and Wurno experienced moderately wet conditions between 1982 and 1991. It was further observed that the whole region was dominated with near normal condition except Sabon Birni and Isa LGAs that experienced extremely, severely and moderately wet condition between 1992 and 2001. In contrast, the SPI values for over 90% of the state  between 2002 and 2011 fall within the severely dry conditions. Findings further showed that change scenarios observed from the derived NDVI and SPI maps indicated that the climatic variability currently being experienced is likely to increase and intensify in future. It is obvious that urgent attention on drought management over this region is needed.Keywords: Drought, SPI, NDVI, Vegetation Cover, Landsat Imageries, Northern Nigeri

In vitro antibacterial, antioxidant and cytotoxic activity of acetone leaf extracts of nine under-investigated Fabaceae tree species leads to potentially useful extracts in animal health and productivity

BACKGROUND: The Fabaceae family is the second largest family of medicinal plants, containing more than 490 species which are being used as traditional medicine. The aim of this study was to determine the antioxidant and antibacterial activity as well as the cytotoxicity of acetone leaf extracts of nine tree species from the Fabaceae family that have not been investigated well previously for possible use in animal health and production. METHODS: The antibacterial activity was determined by a serial microdilution method against three Gram-positive and three Gram-negative bacteria. Antioxidant activity was determined using free-radical scavenging assays. The safety of the extracts was ascertained using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on Vero African green monkey kidney cells. RESULTS: Six of the nine acetone extracts had significant antibacterial activity against at least one of the six bacterial species with (MIC 20–80 μg/mL). The Crotalaria capensis extract had the highest activity against Salmonella typhimurium, followed by Indigofera cylindrica with MICs of 20 μg/mL and 40 μg/mL respectively. The Dalbergia nitidula extract had free radical scavenging capacity (IC50 of 9.31 ± 2.14 μg/mL) close to that of the positive control Trolox in the DPPH assay. The Xylia torreana extract also had high activity (IC50 of 14.56 ± 3.96 μg/mL) in the ABTS assay. There was a good correlation between antioxidant activity and total phenolic content (R2 values > 0.8). The extracts had weak or no toxicity to Vero cells, compared to the positive control doxorubicin with the LC50 varying from 10.70 ± 3.47 to 131.98 ± 24.87 μg/mL at the concentrations tested. CONCLUSION: Extracts of D. nitidula, X. torreana, C. capensis and I. cylindrica had a low cytotoxicity and high antimicrobial and/or antioxidant activity. These species are therefore promising candidates for the development of useful antimicrobial/antioxidant preparations with a low cytotoxicity that may be useful in promoting animal health and productivity.The University of Pretoria provided a postdoctoral fellowship to JPD. The National Research Foundation (NRF) and Medical Research Council (MRC) provided funding to support this study.http://www.biomedcentral.com/1472-6882/14/147am201