Abstract
Solid phase extraction (SPE) using Sep-Pak® cartridges is one of the techniques used for fractionation of antioxidant compounds in waste of dabai oil extraction (defatted dabai parts). The aim of this study was to determine the phenolic compounds and antioxidant capacity in crude extracts and several SPE fractions from methanolic extract of defatted dabai pulp and peel. Based on SPE, Sep-Pak® cyanopropyl and C18 cartridges were used to fractionate the antioxidant-rich crude extracts into water and methanolic fractions. Analyzed using LC-MS, flavonoids, anthocyanins, saponin derivatives and other unknown antioxidative compounds were detected in the defatted dabai crude extracts and their SPE fractions. Anthocyanins were the major phenolic compounds identified in the defatted dabai peel and detected in most of the SPE fractions. Methanolic fractions of defatted dabai parts embraced higher total phenolics and antioxidant capacity than water fractions. This finding also revealed the crude extracts of defatted dabai peel have the most significant antioxidant properties compared to the methanolic and water fractions studied. The crude extract of defatted dabai parts remain as the most potent antioxidant as it contains mixture of flavonoids, anthocyanins and other potential antioxidants.
Highlights
Solid phase extraction (SPE) is one of the techniques used in separation of organic and inorganic compounds
The crude extracts and SPE fractions of defatted dabai peel and pulp-peel were studied for their total phenolic content, total anthocyanin content and antioxidant capacity based on in vitro assays and liquid chromatography-mass spectrometry (LC-MS)
Detection of potential phenolic compounds in the crude extracts of defatted dabai peel and pulp-peel, and their respective SPE fractions were based on the spectra obtained
Summary
Solid phase extraction (SPE) is one of the techniques used in separation of organic and inorganic compounds. SPE utilizing Sep-Pak® cartridges has been applied for fractionation and purification of various compounds of interest. SPE is commonly performed using a silica-fused column that chemically bonded. Cyanopropyl (CN), alumina, silica and C18 bonded-phase cartridges had been used for separation and purification of pesticides and dioxins [1,2], even phenolics and flavonoids [3,4]. Extraction and fractionation of phenolic compounds using SPE is no longer a new technique. Fractionation of phenolic compounds by applying Sep-Pak® CN and C18 bonded-phases are not commonly performed as CN bonded phase cartridge is typically used for separation and fractionation of chlorinated pesticides [2]. The CN silica-based polar bonded phase cartridge can be used as a less polar alternative to silica in normal-phase applications; while C18 is the silica-based trifunctionally-bonded octadecyl sorbent, which is a strong and hydrophobic sorbent applies in adsorption of analytes with weak hydrophobicity from aqueous solutions [5]
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