Accessing the potential of the African spider plant (Cleome gynandra) to control Salmonella typhi

Abstract

The African spider plant (Cleome gynandra) is an erect tender annual herb that is highly branched. This popular and nutritious leafy vegetable has been commercialized as a major African indigenous vegetable in Kenya. The African spider plant has also been an antidote for typhoid and poor sanitation-related illnesses. Salmonella typhi is common with an estimated annual global incidence of 26.9 million cases, and causes 200,000 deaths annually due to mismanagement of water resources and poor sanitation. To validate the medicinal myth, this study aimed to evaluate the efficacy of crude extracts from the African Spider plant, Cleome gynandra against Salmonella typhi the leaf extracts of this vegetable were tested for activity against cultures of Salmonella typhi haplotype H58 in vitro. Fresh leaves were homogenized in sterile distilled water (SDW) at 1:2 wt/vol ratios. Extraction was done overnight at 4^○C and then centrifuged at 1500rpm for 5 minutes. The supernatant was sterilized through 0.2µm Millipore filters and diluted up to x10 ^-3. About 40µlof each diluted extract was loaded onto sterile discs and allowed to air dry under sterile conditions. Similar volumes of Ampicillin at 10µl and SDW were used as positive and negative controls respectively. About 100µl of x10 ^-7 diluted suspensions of Salmonella typhi were inoculated and spread dry on Muller Hilton agar plates. The preloaded discs were then placed radially at a 6cm circumference on the inoculated 9cm Petri plates. The plates were then incubated at 37^○C for 24 hours and growth inhibition zones measured (mm) values were compared statistically using one-way ANOVA to the controls and inference made. All the test crude extracts suppressed the growth of Salmonella typhi significantly compared to SDW controls (p=0.00000136). Straight extracts at 20mg bioactive compound had significantly high (p=0.00000136) bioactivity compared to x10 ^-1 and x10 ^-2 dilutions but significantly lower than the Ampicillin control. Interestingly, extracts diluted to x10 ^-2 with 5mg bioactive compounds suppressed salmonella typhi significantly (p< 0.001). Cleome gynandra has therefore demonstrated antibacterial properties against Salmonella typhi, thus gradually utilizing these plant leaves at high concentrations is recommended to suppress the infections caused by Salmonella typhi pathogenic bacteria.