Total Phenolic Content and Antioxidant Capacity of Different Parts of Cucumber ( Cucumis sativus L.)

Phytochemical and Antioxidant Profile: Cucumber Pulp and Leaves Extracts

BACKGROUND: Many vegetables and fruits have been shown to be sources of antioxidant such as lemons, apples, cabbage, mangoes, beets, and guavas   AIM: This research aimed to determine antioxidant activity of Cucumis sativus L. (cucumber) pulp and leaves extracts using DPPH and CUPRAC methods, total phenolic content (TPC), total flavonoid content (TFC), correlation of TPC and TFC on antioxidant activity, correlation between the two methods, identification of marker, and total marker content.   METHODS: Antioxidant activity was examined by determining IC50 and AAI of DPPH and EC50 and AAI of CUPRAC. TFC and TPC was measured using UV-visible spectrophotometer. Correlation of TPC and TFC on antioxidant activity was analysed by Pearson’s method.   RESULTS: AAI of DPPH of cucumber pulp and leaves extracts in the range of 0.22 - 2.18, whereas AAI of CUPRAC 0.07 - 0.95. All extracts showed antioxidant activity. Ethyl acetate cucumber pulp extract had highest antioxidant by DPPH assay, whereas n-hexane cucumber leaves extract had highest antioxidant activity by CUPRAC assay. Ethyl acetate cucumber leaves extract had highest TFC value (21.47 g QE/100 g) and TPC value (2.34 g GAE/100 g). Flavonoids in cucumber pulp extract contributed to antioxidant activity of CUPRAC method and phenolic compounds in cucumber pulp extract gave a contribution to antioxidant activity of DPPH method. Quercetin content as marker in ethanol cucumber pulp extract was 0.00114%. AAI CUPRAC and DPPH of cucumber leaves extract showed positive correlation but not significant.   CONCLUSION: Antioxidant activity between CUPRAC and DPPH methods on cucumber extracts were not linear.

Genetic and Pre- and Postharvest Factors Influencing the Content of Antioxidants in Cucurbit Crops

Cucurbitaceae is one of the most economically important plant families, and includes some worldwide cultivated species like cucumber, melons, and squashes, and some regionally cultivated and feral species that contribute to the human diet. For centuries, cucurbits have been appreciated because of their nutritional value and, in traditional medicine, because of their ability to alleviate certain ailments. Several studies have demonstrated the remarkable contents of valuable compounds in cucurbits, including antioxidants such as polyphenols, flavonoids, and carotenoids, but also tannins and terpenoids, which are abundant. This antioxidant power is beneficial for human health, but also in facing plant diseases and abiotic stresses. This review brings together data on the antioxidant properties of cucurbit species, addressing the genetic and pre- and postharvest factors that regulate the antioxidant content in different plant organs. Environmental conditions, management, storage, and pre- and postharvest treatments influencing the biosynthesis and activity of antioxidants, together with the biodiversity of this family, are determinant in improving the antioxidant potential of this group of species. Plant breeding, as well as the development of innovative biotechnological approaches, is also leading to new possibilities for exploiting cucurbits as functional products.