Abstract
This study was aimed at evaluating the effect of extraction methods on the antibacterial activity of Citrullus lanatus seed extract. C. lanatus (watermelon) is a popular fruit consumed all over the world. Three solvents were used for the extraction process: chloroform, methanol and distilled water while two extraction conditions- cold extraction and Soxhlet extraction (coded as hot in this study) were employed. Antibacterial activity of the seed extracts was determined by agar well diffusion method. The seed extracts were tested against clinical isolates including Staphylococcus sp., Escherichia coli, Proteus sp., Klebsiella sp. and a type Pseudomonas aeruginosa (ATCC 27853). It was observed that the cold methanol extracts had the highest antibacterial effect on Staphylococcus sp. followed by hot methanol extract while cold chloroform extract showed no antibacterial activity. In the presence of P. aeruginosa only the hot methanol and chloroform extracts showed significant antibacterial potentials (p≤0.05). Also, saponins which have been implicated in antimicrobial activity were found to be present in moderate and high concentrations in the hot and cold methanol extracts respectively. Results of this study reveal that the kind of solvent employed as well as the conditions for extraction (cold maceration and Soxhlet extraction) influenced the efficacy of the extract against specific test organisms. Furthermore, the presence of saponins may have influence the relatively high zone of inhibition recorded with cold and hot methanol extracts against some of the test organisms. Key words: Watermelon seed, antibacterial, Soxhlet extraction, cold maceration, solvents.
Highlights
Citrullus lanatus commonly called watermelon is a popular fruit in many parts of the world and it is notable for its high water content and attractive look
Results of this study reveal that the kind of solvent employed as well as the conditions for extraction influenced the efficacy of the extract against specific test organisms
The result reveals that the cold chloroform and hot chloroform extracts (CCE and HCE) had the same phyto-constituents; this was the case with the cold and hot methanolic extracts (CME and hot methanol extract (HME))
Summary
Citrullus lanatus commonly called watermelon is a popular fruit in many parts of the world and it is notable for its high water content and attractive look. Most of the information available on the antibacterial activity of C. lanatus seed have made it clear that cold maceration is popularly used for extraction of C. lanatus plant parts (Okunrobo et al, 2012; Omigie and Agoreyo, 2014; Oseni and Okoye, 2013); and in few cases Soxhlet extraction (Meena and Patni, 2008; Oyeleke et al, 2012). This has brought about the need to compare extraction methods in order to determine which method will yield the highest antibacterial effect on the organisms. The aim of this study was to examine the effect of extraction solvents and extraction conditions on the antibacterial potential of the seed extracts of C. lanatus
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