Analytical evaluation of phenolic compounds and minerals of Opuntia robusta J.C. Wendl. and Opuntia ficus-barbarica A. Berger

In this study, 19 phenolic compounds were detected using high-throughput instrument ultra performance liquid chromatography with electrospray ionization tandem mass spectrometry (UPLC–ESI–MS/MS) in Opuntia ficus-barbarica A. Berger and Opuntia robusta J.C. Wendl. fruits. The five macro- and five micro-minerals determined in both species were analyzed using inductively coupled plasma–mass spectrometer. The phenolic compounds, mineral content, and the antioxidant capacity of the fruits of O. robusta and O. ficus-barbarica were analyzed. All phenolic compounds and minerals varied significantly between the two species. The total of phenolic compounds content was calculated as 69.237 and 66.385 mg kg⁻¹, respectively, in O. ficus-barbarica and O. robusta. Ferulic acid was the highest quantities, 31.620 and 26.931 mg kg⁻¹ in O. robusta and O. ficus-barbarica, in all phenolic contents, respectively. The macroelements calcium and potassium were the most abundant in both Opuntia species. The antioxidant activity of O. ficus-barbarica and O. robusta fruit samples was measured in the extracts of hexane, ethyl acetate, methanol, and water. The DPPH assay of Opuntia samples displayed a good radical scavenging inhibition, similar to butylated hydroxyanisole and butylated hydroxytoluene standards, as half maximal inhibitory concentration IC₅₀ = 69.32 and 67.57 μg mL⁻¹ in ethyl acetate extracts of O. ficus-barbarica and O. robusta fruits, respectively. This work presents a suitable method for the extraction, detection, and quantification of phenolic compounds by UPLC–ESI–MS/MS. MS/MS determination for multiclass determination was validated in Opuntia samples obtaining good results. Abbreviations: ABTS, 2,2′-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid; AChE, acetylcholinesterase; BChE, butyrylcholinesterase; BHA, butylated hydroxyanisole; BHT, butylated hydroxytoluene; DPPH, 2,2-diphenyl-1-picrylhydrazyl; DTNB, (5,50-Dithio-bis(2-nitrobenzoic)acid; ICP/MS, inductively coupled plasma/mass spectrometer; LoD, yhe limit of detection; MRM, multiple reaction monitoring; QEs, quercetin equivalents; PEs, pyrocatechol equivalents; R², correlation coefficients; r, Pearson’s correlation coefficient; SD, standard deviation; TIC, total ion chromatogram; UPLC–ESI–MS/MS, ultra performance liquid chromatography with electrospray ionization tandem mass spectrometry