A potential approach to valorize citrus peel (P) in addition to seed (S), which remain wastes of the juice abstraction manufacturing, is to custom them as accepted bionematicides. However, information on the limonoids as well aspolyphenolics contents of the peel and seeds of Citrus aurantium var. deliciosa were limited. In the present study, methanolic extracts of the peel and seeds of C. aurantium were analyzed using high performance liquid chromatography (HPLC). For activity of P and S against egg emerging and transience of juveniles of root-knot nematode, Meloidogyne incognita, reniform nematode, Rotylenchulus reniformis and citrus nematode, Tylenchulus semipenetrans was investigated. HPLC analysis of limonoids for the tested extracts was performed. Total limonoids in (S) is nearly twice its amount in P. Both extracts contained nomilin, intense bitter limonoid. Nomalin amounted 288.77 and 514.67 mg/100 g extracts of P and S, respectively. Moreover, limonin was detected in P and S (57.85 and 195.74 mg/100 g, respectively). Peel was rich in phenolics contents than seed (49.80 and 10.54 mg/100 g, respectively) as gallic acid. Also, peels and seeds exhibited comparable flavonoids contents. Moreover, HPLC analysis of phenolics and flavonoids revealed that P was rich in flavones (apigenin, luteolin) and glycosylated flavanones (naringen, hesperidin) than S. Both extracts at the tested concentrations inhibited egg hatching at each exposure period for each nematode species compared to those of the control. Egg hatching was maximum in control. Generally, the percentages of hatching gradually increased with time and decreased with concentration. In other words, the percentages of hatching were maximum at 96 h and minimum at 24 h. Exposure to 1000 ppm extract caused the least percentages hatching of egg, followed by those of 750 and 500 ppm. As for juvenile mortality, the percentages mortality was concentration- and exposure period-dependent as the percentage nematode mortality increased with increasing the concentration and time of exposure.
Key words: Mandarin, limonoids, phenolics, peel, seed, plant-parasitic nematodes.
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