Regulation of pro-inflammatory enzymes by the dragon fruits from Hylocereus undatus (Haworth) and squalene - its major volatile constituents

Background: Hylocereus undatus produces fruits known as dragon fruit (Pitaya). The fruit and other parts of Hylocereus species are used for the treatment of diuretic, gastritis, kidney problems, and wound healing. Objectives: To investigate anti-inflammatory properties of the flesh and peel of Pitaya and to identify the major bioactive constituent(s). Materials and Methods: The flesh and the peel of the fruit were blended separately with water, vacuum-distilled, freeze-dried, and then used for the bioassay tests against the 5-Lipoxygenase (5-Lipox), Cyclooxygenase-2 (COX-2), and Acetylcholinesterase (AChE) enzymes. Results: Squalene appeared to be the dominant constituent (13.2%) in the flesh of the fruit. The crude flesh extract and the squalene showed strong activities against AChE with inhibition percentage >80% (IC50 <43 μg/mL). The peel was active against 5-Lipox with inhibition of 81%. Inhibition percentages recorded for the positive controls used were 77% for Zileuton against 5-Lipox (IC5028 μg/mL), 85% for the Galantamine against AChE (IC50 16 μg/mL), and 86% for the Celecoxib against COX-2 (IC5032 μg/mL). For maximum efficacy against the three enzymes, squalene showed the best performance with EC50values ranging between 46 and 47 μg/mL. Conclusion: The findings showed that Pitaya has a significant potential for the management of inflammatory conditions through different mechanisms including, leukotriene, prostaglandins, and cholinergic pathways. To the best of our knowledge, identification of squalene in the dragon fruit flesh and the validated biological activities were not reported previously and therefore accounted for the novelty of the study.