The Bioactive Compounds and Fatty Acid Profile of Bitter Apple Seed Oil Obtained in Hot, Arid Environments

Abstract

Bitter apple or tumba (Citrullus colocynthis L.) is a prostrate annual herb belonging to the Cucurbitaceae family. It is highly tolerant against multiple abiotic stresses like drought, heat, and soil salinity and can easily grow on very marginal soil, even on sand dunes in hot, arid regions. Tumba fruit is a fleshy berry 5–10 cm in diameter and of a pale yellow color at ripening. The tumba fruit used in this research was harvested from the ICAR-CIAH, Bikaner research farm. The seeds were separated, and their oil was extracted to analyze its physical characteristics and composition (phytochemical compounds, fatty acid profile, etc.). The seeds of the tumba fruit contained 23–25% golden-yellow colored oil with a specific gravity of 0.92 g/mL. The extracted oil contained appreciable amounts of phytochemical (bioactive) compounds like phenolics (5.39 mg GAE/100 g), flavonoids (938 mg catechin eq./100 g), carotenoids (79.5 mg/kg), oryzanol (0.066%), and lignans (0.012%), along with 70–122 mg AAE/100 g total antioxidant activity (depending on the determination method). The results of fatty acid profiling carried out by GC-MS/MS demonstrated that tumba seed oil contained about 70% unsaturated fatty acids with more than 51% polyunsaturated fatty acids. It mainly contained linoleic acid (C18:2n6; 50.3%), followed by oleic acid (C18:1n9; 18.0%), stearic acid (C18:0; 15.2%), and palmitic acid (C16:0; 12.4%). Therefore, this oil can be considered as a very good source of essential fatty acids like omega-6 fatty acid (linoleic acid), whereas it contains a lower concentration of omega-3 fatty acids (α-linolenic acid) and hydroxy polyunsaturated fatty acids. In addition, it also contains some odd chain fatty acids like pentadecanoic and heptadecanoic acid (C15:0 and C17:0, respectively), which have recently been demonstrated to be bioactive compounds in reducing the risk of cardiometabolic diseases. The results of this study suggest that tumba seed oil contains several health-promoting bioactive compounds with nutraceutical properties; hence, it can be an excellent dietary sourc