FATTY ACIDS, TOCOPHEROLS, STEROLS, PHENOLIC PROFILES AND OXIDATIVE STABILITY OF CUCUMIS MELO VAR. AGRESTIS OIL

Abstract

ABSTRACT Oil extracted from the seeds of Cucumis melo var. agrestis, collected from Ghibaish (sandy soil) and Gezira (heavy clay soil) provinces in Sudan, was studied in terms of the profile of fatty acids, tocopherols and sterols as well as phenolic compounds and oxidative stability by Rancimat (Metrohm AG, Herisau, Switzerland). The predominant fatty acid was 18:2n‐6, representing 61.3 and 61.4% for Ghibaish and Gezira samples, respectively. There were no variations among the contents of 16:0, 18:0, 18:1n‐9 and 18:2n‐6 between the two samples. γ‐Tocopherol was the predominant tocopherol in both samples, representing 80.7 and 77.6% of the total tocopherols, respectively, followed by α‐tocopherol at 18 and 21%, respectively. Total sterol content was 3,879.0 and 3,785.0 mg/kg for Ghibaish and Gezira samples, respectively. The main sterol of the two oils was β‐sitosterol. The two samples showed an oxidative stability of 5.9 and 5.7 h, respectively. The content of total phenolic compounds was determined in each sample according to the Folin‐Ciocalteau method as 33.0 and 31.9 mg/g of dry product, respectively. The phenolic compounds of the oil were separated using a solid phase extraction. The fractions were studied by high‐performance liquid chromatography with diode‐array detection, which revealed four peaks in the two samples. The major components were catechin, vanillic acid, sinapic acid and callistephin. There was little variability according to location between the two samples.PRACTICAL APPLICATIONSTwo samples from dried seeds of Cucumis melo var. agrestis were collected. Seeds were crushed and ground using a grinding mill; the oil was extracted from the ground seeds by extraction with petroleum ether in a Soxhlet apparatus, and the physicochemical properties of C. melo var. agrestis oil were determined. The fatty acid and sterol composition were investigated using gas chromatography; the different tocopherol homologs were identified by high‐performance liquid chromatography (HPLC), and the oil oxidative stability was studied by Rancimat (Metrohm AG, Herisau, Switzerland) apparatus. The phenolic compounds were extracted from the obtained oil and then identified by HPLC with diode‐array detection.