Researchers believe that there is still a huge number of antiinfection materials that have not been discovered in nature. In addition, to date, only 10% of all vascular plants (containing vessels to transport fluids inside) have been examined to search for medicinal compounds that may contain them. Seed oils of watermelon (Citrus lanatus) of Cucurbitaceae were analyzed by gas chromatography/mass spectrometry (GC-Ms) revealed the presence of 9 fatty acids, dicarboxylic acids, and carried out with all parts of plant 18 free amino acids, including essential and nonessential amino acids by automatic amino acid analyzer. Additionally, determination the antimicrobial activity of the18 free amino acids of watermelon (Citrus lanatus) against the microorganisms, showed the strong susceptibility and it was also compared with selected antibiotics. However, its activity varies with the nature of plant seeds and organisms. Various parts of watermelon plant have been known with their significant pharmacological activity attributed to phytochemicals such as phenols, saponins, tannins, glycoscide, and alkaloids in their seed oil. © 2022 Elsevier Inc. All rights reserved.