Abstract

SUDANESE OKRA SEED OIL: PHYSICOCHEMICAL CHARACTERISTICS AND ANTIOXIDANT ACTIVITY OF WILD AND CULTIVATED TYPES

Azhari Siddeeg*, Douha Abdelwahab, Ammar Al-Farga, Ayah Talal Zaidalkilani

ABSTRACT

The aim of this study was to conduct a comparative analysis of Sudanese cultivated and wild varieties of okra (Ablemoschus esculentus (L.) Moench) seeds, including physicochemical analysis, volatile compounds, and antioxidant activity. Standard methods were used to determine the physicochemical characteristics, and the volatile components were determined by using gas chromatography, while antioxidant activity was determined by determining total phenolic content and Diphenyl picrylhydrazyl (DPPH). It was found that the oil, carbohydrates, and moisture contents were higher in cultivated seeds (24.69, 51.69, and 6.51%, respectively) compared with wild seeds (12.17, 48.69, and 4.59%, respectively), while protein, fiber, and ash (14.50, 12.62 and 7.34%, respectively) were higher in wild type compared with cultivated seeds (8.16, 3.26 and 5.69%, respectively). Sodium and potassium contents were found to be higher (0.22 and 0.24 g/100g) in the wildvariety compared with the cultivated variety (0.19 and 0.20g/100g). There was no significant difference between varieties in free fatty acids content, acid value, and unsaponifiable matter. Iodine value, peroxide value, and saponification value of wild oil were 145.1, 7.3 milliequivalent peroxide/Kg oil, and 190.74 mg KOH/gm oil, respectively, compared with 148.2, 9.8 milliequivalent peroxide/Kg oil and 187.94 mg KOH/gm oil, respectively, for cultivated oil. There were no significant differences (p<0.05) among the specific gravity and refractive index of both varieties, while viscosity was found to be higher in the oil of the wild variety (55.0 centipoises) in comparison to cultivated okra seed oil (45.0 centipoises). Six components were identified as volatile components; 9, Octadecadienoic acid, Z, methyl ester was found in the highest amount in wild and cultivated varieties (38.27 and 38.29%, respectively), while Heptadecanoic acid, 16-methyl-, methyl ester was the lowest content (6.45 and 6.24%, respectively). The total phenolic content of the wild variety was 214.50 mg Gallic acid equivalent/100 g against 179.25 mg for the cultivated variety. DPPH radical scavenging activity showed the strongest antioxidant activity (80.75%) in wild seeds compared with 73.50% for the cultivated variety. Thus, the output of this research indicated that Sudanese okra seed varieties, wild and cultivated, are good sources of nutrients and antioxidants, which could help in alleviation of difficulties related with fat oxidation.

Keywords: Okra seed, physicochemical properties, volatile compounds, antioxidant activity.