Antimicrobial and time-kill kinetics of the aqueous extract of Citrullus lanatus (Thunb.) seeds

Abstract

This study evaluated the antimicrobial property of the aqueous extract of Citrullus lanatus (watermelon) seeds and its concentration-effect relationship (time-kill studies) on typed bacterial and fungal strains. Crude powdered seeds of Citrullus lanatus were extracted by maceration with water. Antimicrobial assay of the aqueous extracts was determined against Bacillus subtilis (NCTC 8236), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 10145), Staphylococcus aureus (ATCC 25923), and Candida albicans (ATCC 24433) using standard microbiological methods. A total of 106 CFU/mL of each test strain was used as a baseline to carry out the time-kill studies. Extract concentration at minimum inhibitory concentration (MIC), 2MIC and 4MIC were used over a period of 24 hours. Aqueous extract had an intermediate antibacterial activity with inhibition zone diameters (IZD) of 15 - 18 mm and MIC range of 2.5 - 20 mg/mL. Time-kill studies showed a bacteriostatic, non-concentration dependent mode of antimicrobial activity with characteristic regrowth for all test strains. Citrullus lanatus seeds aqueous extract exhibited antimicrobial activity with a bacteriostatic, non-concentration dependent mode of action against test bacterial strains. Further studies aimed at isolating and purifying the antimicrobial principle in the aqueous extract of C. lanatus seed is warranted as this could serve as a potential new antibiotic for treating microbial infections.

Recent Advances in the Antibacterial Activities of Citrullus lanatus (Watermelon) By-Products

“…Another interesting study was conducted by Babaiwa et al [109], who evaluated the antibacterial efficacy of the aqueous extract derived from C. lanatus seeds and investigated the concentration-effect relationship through time-kill studies. The crude powdered seeds of C. lanatus were subjected to extraction through the process of maceration using water as the solvent.…”

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“…In addition, the WMSs ethanolic isolate has strong antibacterial properties also can be utilized as a convenient naturalist source of antimicrobial compounds [32]. Furthermore, B. subtilis, B. cereus, S. typhi, E. coli, P. fluorescence, P. aeruginosa, and S. aureus can be treated with watery and methanolic isolates of WMSs powders [33,34]. The antibacterial properties of raw ethanol, hexane, and chloroform isolates of Citrullus lanatus seeds, stems, fruits, and leaves were tested versus microorganisms, including bacteria and fungi [35].…”

Review of studies published on the medicinal importance of different parts of Citrullus lanatus in the last ten years

“…The antimicrobial ef f icacy of methanolic extract of CL seed was reported by Sathya and Shoba (2014). Other groups of authors that attested to the good antibacterial ef f ects of CL seed were Adunola et al, (2015); Braide et al, (2012); Sathya and Shoba (2014); Babaiwa et al, (2020) and Gill et al, (2010). Hameed et al, (2020) emphasized the importance of melanin f ound in crude chlorof orm, hexane and ethanol leaves, stem, f ruits, and seeds extracts of CL as a good antibacterial agent due to the presence of tannins, saponins, f lavonoids, cyanogenic glycosides f ound in the extract.…”