Phytochemical Elucidation and Antioxidant Activity of Seeds from Three Prickly Pear (Opuntia ficus-indica L.) Cultivars from Algeria
Date
2023-01-21
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Abstract
In this study, the characterization of fatty acids and secondary metabolites in seeds of three cultivars of Opuntia ficus-indica L. (O. ficus-indica, yellow, orange, and green) harvested from the Souk Ahras area in Northeast Algeria was performed. The antioxidant activity of seed extracts was also assessed by using two methods, namely FRAP and DPPH tests. Results show that total phenolic content (TPC) ranged from 63.02 to 81.80 mg gallic acid equivalents (GAE)/100 g of seeds. The yellow cultivar had the highest TPC, followed by the orange and green cultivars. Concerning flavonoids and tannins, the orange cultivar showed higher concentrations, corresponding to 2.97 mg quercetin equivalent (QE)/100 g and 5.60 mg catechin equivalent (CE)/100 g, respectively. Analysis of the seed extracts by HPLC revealed the presence of phenolic compounds, including gallic acid and chlorogenic acid, while the GC analysis of oil showed that prickly pear oil is a major source of essential fatty acids (C18:2). The antioxidant activities of extracts from the three cultivars were comparable. The EC50 for the reduction of ferric iron was almost 0.05 g/mL for all extracts. Regarding the scavenging of DPPH, green and yellow cultivars showed the highest capacity (EC50 = 0.26 g/mL). Linear correlations between the content of some antioxidants (flavonoids, tannins) and different activities were observed, indicating their participation in the latter. Above all, a significant inverse correlation between the total flavonoid content and the EC50 calculated for the reducing activity of seed extracts was observed (r = −0.657; p ≤ 0.05). Overall, the results indicate that the seeds of O. ficus-indica growing in Algeria can be exploited as valuable sources of table oil, cooking oil, and antioxidants.
Keywords:
Opuntia ficus-indica; seeds; antioxidants; polyphenols; antiradical activity
Description
Overall, the results of this study show that the seeds of three different cultivars of O. ficus-indica from the Souk Ahras area of Algeria represent a valuable source of nutrients and bioactive compounds. An oil rich in essential fatty acids can be extracted that can be potentially used as table or cooking oil. Moreover, the results show that these seeds contain significant levels of antioxidants. The concentration of total phenolic compounds was higher in the yellow cultivar, while flavonoid and tannin contents were higher in the orange one. The antioxidant activity of seed extracts is significant, but a variability that depends on the cultivar was observed in the different assays performed. The green and orange cultivars had a higher reducing power, while yellow and green cultivars had higher anti-radical activity. Positive and negative correlations were observed between the different activities and the concentrations of antioxidants measured, indicating that these compounds participate, according to the concentration, in antioxidant and antiradical effects. Also, these observations indicate that the concentration factor alone does not explain the results obtained. Therefore, it would be desirable to purify and identify the compounds present in seed extracts, apply more experimental protocols, and carry out the test on other varieties of prickly pear.
Finally, for a complete valorization of this plant species in Algeria, the current study should be integrated with analyses of other parts of the fig tree that are considered as waste in the future, and with further bioactivity tests on whole extracts and isolated chemical constituents.