In Korea, the Rural Development Administration (RDA) is building a national food composition database (DB), and research is underway to supplement and add information on functional ingredients (phytosterols, phospholipids (PLs), carotenoids, etc.) con...
In Korea, the Rural Development Administration (RDA) is building a national food composition database (DB), and research is underway to supplement and add information on functional ingredients (phytosterols, phospholipids (PLs), carotenoids, etc.) contained in K-agricultural and food resources. Vegetables and seaweeds are commonly consumed foods in Korea and contain a variety of physiologically active substances. However, the DB does not provide information on the types and contents of fat-soluble components (phytosterols, PLs, carotenoids) in these vegetables and seaweeds. Therefore, this study analyzed fat-soluble components in vegetables and seaweed and validated analytical methods to confirm the reliability and suitability of each method.
The crude fat content of vegetables and seaweeds ranged from 0.66-9.75 g/100 g dry weight (DW). Chlorophyll and total carotenoids were measured as fat-soluble pigments in vegetables and seaweeds. Among vegetables, chives had the highest total chlorophyll and total carotenoid contents, at 904 μg/g DW and 191 μg/g DW, respectively. Among seaweeds, mojaban had the highest total chlorophyll (490 μg/g DW) and total carotenoid (161 μg/g DW) (p<0.05).
Sterol contents in vegetables and seaweeds were measured using gas chromatography-mass spectrometry (GC-MS)/selective ion moniotring (SIM). The specificity of the sterol analysis method was confirmed by the relative retention time (RRT) of each sterol standard. The RRTs of the sterol standards ranged from 1.54-2.11, and the RRTs within samples were also consistent at 1.54-2.11. The linearity of each sterol standard was confirmed by the coefficient of regression (R2), which was 0.99 higher. The recovery rate was measured by adding 0.04 mg/mL of each sterol to the sample, and the result was 101-104%, which was in accordance with the AOAC guideline. The limit of detection (LOD) for sterol analysis was 0.0015-0.0023 mg/mL, and the limit of quantification (LOQ) was 0.0024-0.0049 mg/mL. Cholesterol (5-48 mg/100g DW) and β-sitosterol (4-146 mg/100g DW) were commonly identified in vegetables and seaweeds, while stigmasterol (7-129 mg/100g DW) was identified in vegetables. And lathosterol (4 mg/100g DW) was identified in sea string. Nine vegetables and seaweeds samples containing cholesterol and lathosterol were qualitatively analyzed using ultra-high-performance liquid chromatography (UHPLC)-tandem MS (MS/MS). Cholesterol was confirmed in all samples.
The PLs content of the vegetables and seaweeds were measured using an HPLC-evaporative light scattering detector (ELSD), and the analytical method was validated. Specificity was excellent, with a resolution of 1.66-4.93 for each PLs standards (greater than 1.5), and linearity was excellent, with an R2 value of 0.99 higher. The LOD for PLs analysis was 0.20-0.50 μg/mL, and the LOQ was 0.58-1.20 μg/mL. The PLs identified in the vegetables and seaweeds were phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol (PI), and lysophosphatidylcholine (LPC). The major PLs in vegetables and seaweeds were PC (8-216 mg/100 g DW), PE (0.49-106 mg/100 g DW), and PI (2-126 mg/100 g DW). LPC (1-8 mg/100 g DW) was present in small amounts or was unknown. The total PL content of vegetables and seaweeds ranged from 1.86-449 mg/100g DW. The ratio of total phospholipid to crude fat was highest in beet(14.19%) and sea string(8.55%), while kale(1.23%) and agar(0.24%) had the lowest.
The fatty acid content of vegetables and seaweeds was measured using a GC-flame ionization detector (FID). The major fatty acids in vegetables were palmitic acid, linoleic acid, and α-linolenic acid. The major fatty acids in seaweeds were palmitic acid, green algae was alpha-linolenic acid, brown algae was arachidonic acid, and red algae was eicosapentaenoic acid (EPA). Unlike other seaweeds, maesaengi contained docosahexaenoic acid (DHA).
This study analyzed the composition of fat-soluble pigments, sterols, PLs and fatty acids in vegetables and seaweeds. Specifically, by validating the analysis methods for sterols and PLs, including cholesterol, we confirmed the reliability and suitability of each analysis method. The results of this study are expected to serve as fundamental data for the National Food Composition DB. Furthermore, by providing a DB of fat-soluble functional components, such as PLs, found in vegetables and seaweeds, which are consumed in large quantities by Koreans due to their dietary habits, we anticipate providing a scientific basis for selecting foods for disease prevention.