# Recent Advances in the Antibacterial Activities of _Citrullus_ _Ianatus_ (Watermelon) By-Products
## 4 Antibacterial Activities of _Citrullus Ianatus_ By-Products
### Seeds
The chemical composition of a plant can be modified by extended drying periods conducted in shaded conditions at ambient room temperature, resulting in potential alterations to its organoleptic characteristics. Consequently, it is advisable to employ oven drying for the preservation of the medicinal properties of watermelon seeds. In a previous study conducted by [PERSON] et al. [9], investigations were also made into watermelon seed extract. Seed powder was mechanically shaken with methanol as a solvent for 24 h at RT. Alkaloids, flavonoids, triterpenoids, and free-reducing sugars were found in the seed extract, while tannins, steroids, and saponins were not detected. The observed antibacterial activity in all examined extracts could potentially be attributed to the presence of alkaloids. The antioxidant activity of methanolic seed extract was measured at 4.2 mg GAE/100 g, ~61% more than the rind extract and ~107% lower than the peel extract. At a concentration of 500 mg/mL of methanolic seed extract, the mean values of inhibition zones for the previously mentioned microorganisms ranged from 9 to 18. The lowest value was observed in Gram-positive _S. albus_ while the highest value was found in Gram-negative _S. somei_. Consequently, MIC values ranged from 2 to 32 mg/mL. Specifically, _S. somei_ displayed the lowest MIC value, while _S. albus_ exhibited the highest. The analyzed extracts showed comparable antibacterial effects against both Gram-positive and Gram-negative bacteria, indicating their potential as a valuable source of antibacterial agents. Further investigations are required to clarify the varying vulnerabilities of different organisms towards watermelon seed extracts by examining the specific compounds within each phytochemical class. A study investigating _C. lanatus_ seed extracts employing four distinct solvents, including acetone, chloroform, dichloromethane, and ether, was conducted by [PERSON] and [PERSON] [110]. The seed powder was mixed with a solvent, dried, and then mixed with the next solvent. The process was continued up to the last solvent, while the dried extract was treated with 1 M NaOH, filtered, and finally processed with 1 M HCl. Three extraction methods were utilized, including shaking, ultrasonic bath-assisted maceration, and microwave oven-assisted maceration. Additionally, the extraction process was conducted in three different polarity modalities: non-serial, serial ascending polarity, and serial descending polarity. Out of the various approaches and modalities mentioned, they selected only one ether extract from the descending design polarity to extract five distinct coumarins (RA1-RA5). The antibacterial efficacy of the individual chemicals was evaluated in vitro using the broth microdilution technique. The pathogen strains that were specifically targeted in this study included only Gram-negative bacteria, such as the pathogens _E. coli_ (25922 ATCC), _S. typhimurium_, _Shigella dysenteriae_, _Haemophilus influenzae_, _Klebsiella pneumonia_, and _P. aeruginosa_, in addition to another _E. coli_ (BAA 1427) bacteria, which is nonpathogenic, as there is a strain present that constitutes a nonpathogenic intestinal microbiota. The MBC values for every coumarin derivative in each bacterium ranged from 0.45 to 16 \(\upmu\)g/mL. In most circumstances, the RA4 derivative has values closer to CiprofloxacinABC values, except for _K. pneumoniae_ and both _E. coli_ strains, where the RA1 derivative was found to be more efficient. Some other bacteria, such as _Clostidium perfringens_, _Bacteroides fragilis_, _Prevotella melaninogeneica_, and _Fusobacterium necrophorum_, were also examined. MBC values ranged from 2-16 \(\upmu\)g/mL. In that case, RA4 was found to be the most efficient coumarin derivative of all, with its values being closest to MBC values from the antibiotic Metronidazolezo. In conclusion, this study has determined the potential of employing these isolated compounds as a source for developing innovative antibacterial agents. The study by [PERSON] et al.