Abstract
In this study, we investigated the formation of stable radicals and compounds related to antioxidants in Camellia japonica seeds using high performance liquid chromatography (HPLC) and X-band electron paramagnetic resonance imaging (EPRI). The C. japonica seed coat extracts exhibited antioxidant activity in both in vitro and cell-based studies. The extracts inhibited reactive oxygen and reactive nitrogen species production in cell-based studies. HPLC chromatograms indicated that hydrophilic antioxidant compounds—namely, gallic acid, gallocatechin, epigallocatechin, caffeine, catechin, epicatechin, and epicatechin gallate—were found in the methanolic extract. Lipophilic antioxidant compounds—including α-tocopherol, γ-tocopherol, β-tocopherol, δ-tocopherol, α-tocotrienol, γ-tocotrienol, and δ-tocotrienol—were found in the hexane extract. EPRI primarily detected paramagnetic species in seed coats. These radical species were stable organic radicals based on the peak-to-peak line width and g-values. The signals from these stable radicals were strong and stable with a g-value of 2.002. Noninvasive EPRI of the radicals present in C. japonica seeds indicated that the stable radicals were essentially located in the seed coats. The EPRI of the cotyledon demonstrated that additional radicals were localized at an apex of the cotyledon. The results indicated that the stable radicals detected by EPRI and the hydrophilic and lipophilic antioxidant compounds analyzed by HPLC were related to antioxidant reactants and products.
Highlights
The tree Camellia japonica (C. japonica) flowers between January and March
The current study proposed an antioxidant determination technique in plant seeds using a non-invasive technique called electron paramagnetic resonance
Hydrophilic (ME) and lipophilic (HE) C. japonica seed coat extracts were determined for antioxidant activity in both reactive oxygen species (ROS) and RNS systems using in vitro and cell-based studies
Summary
The tree Camellia japonica (C. japonica) flowers between January and March. The flowers usually last three to four weeks, and, during this time, the fruit develops. Each cavity of the spherical fruit contains up to two small brown seeds that are no more than two centimeters in diameter. The cotyledons of these seeds are used in food as well as cosmeceuticals. In addition to minerals, such as calcium and magnesium, the seeds contain fatty acids, namely, oleic acid and stearic acid. Oleic acid, which is a monosaturated fatty acid, has been reported to have health benefits in humans [1,2]. Many other features of C. japonica seed coats remain to be determined
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