The antioxidant activity and the chemical composition of methanol extracts from peel and pulp belonging to two species of Tunisian prickly pears Opuntia ficus indica (spiny and thornless forms) and Opuntia stricta have been studied. The antioxidant capacity was measured by DPPH radical scavenging activity. The total phenolic compound (TPC) and the total flavonoid content were determined by the Folin–Ciocalteu method and colorimetric method, respectively. The phenolic compounds were identified and quantified by high-performance liquid chromatography (HPLC) coupled with an electrospray ionization mass spectrometry (ESI-MS). The results showed that O. stricta fruits present the best antioxidant activities than the two forms of O. ficus indica, while the TPC was more important in O. ficus indica than in the O. stricta fruits. The peels have higher flavonoids than pulp, and the thornless variety has more flavonoid than the spiny. The RP-HPLC and ESI-MS analysis detected two classes of phenolic compounds and betalain pigments. Isorhamnetin derivatives are the dominant flavonol glycoside identified in O. ficus indica (spiny: 65.25 μg·g−1; thornless: 77.03 μg·g−1) and O. stricta peels (19.22 μg·g−1).
This study was carried out to evaluate the phytochemical constituents and antioxidant potential of the leaves and flowers extracts of Halimium halimifolium in order to validate the medicinal potential of this herb. The antioxidant activity of alcoholic and aqueous extracts was evaluated using 2, 2-diphenyl-l-picrylhydrazyl (DPPH), 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) assays. The total polyphenol, flavonoid and tannin content were determined according respectively to Folin-Ciocalteu method, Zhishen method and Broadhurst method. The leaves of H. halimifolium had greater antioxidant activity than flowers by DPPH and ABTS assays. The ethanol extract of the leaves exhibited the better antioxidant activity by DPPH assay (IC50 = 1.19 µg.mL-1), the n-butanol by ABTS assays (IC50 = 1.73µg.mL-1). As opposed to FRAP method the flowers had greater antioxidant activity as leaves. Ethyl acetate extract exhibited better antioxidant activity (IC50 = 15.5 mmol Fe 2+ .g-1). The obtained results showed that the extracting solvent significantly influenced the antioxidant property estimations of Halimium halimifolium. The ethanol is a recommended solvent for extracting antioxidants from this plant. The antioxidant activity determined by DPPH, ABTS and FRAP demonstrated a linear relationship with their polyphenols, flavonoids and tannins content.
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