Evaluation of the Effects of Drying Methods on Phytochemicals in Thevetia neriifolia Parts as a Potential Rodenticide

Abstract

Synthetic rodenticides are effective and rapid in controlling rats; however, they are toxic to non-target species including humans, as well as the environment. Thevetia neriifolia (Pers.) K. Schum different parts however, reportedly have toxic effects on rodents. Effects of fresh, air and sun-drying methods on phyto-constituents of flowers, leaves, root, seed and stem bark and its potentiality in the control of rodents were therefore, investigated in this study. Analyses showed the presence of free agyclones: Thevetin A (1.88 mg/g) and B (1.64 mg/g), cardiac glycosides (1.49 mg/g), alkaloid (1.36%) and digitoxin (1.32 mg/g) in highest concentrations. Phenols (6.90x10-2 mg/g), (2.21x           10-2 mg/g) from flavonoids, Tannins (1.13x10-2 mg/g) and steroids (6.70x10-3 mg/g) were in moderate concentrations while antraquinone (0.70x10-3 mg/g) was the lowest. Antraquinone            was also not detected in flower parts. Sun-dried parts had highest concentrations of Thevetin A (1.47 mg/g), cardiac glycosides (1.39 mg/g) and Thevetin B (1.27 mg/g), followed by air–drying           for cardiac glycoside (1.33 mg/g) and Thevetin A. fresh for Thevetins A (1.25 mg/g), and B            (1.10 mg/g), and cardiac glycoside (0.93 mg/g) and tannins, respectively while antraquinone and terpenes were undetected. Higher phytochemicals content were in leaf followed by stem bark, then air-drying due to interaction of sun-drying methods and parts of plant. Free aglycones, Thevetins A and B, cardiac glycosides, digitoxin, oleadrin, tannins, phenols and steroids in Thevetia neriifolia plant parts were not affected by different drying methods. Therefore, the relatively high cardiac glycosides and free aglycone in different parts of Thevetia neriifolia may be exploited for natural rodenticidal purpose.