The Quality Determination of Selected Commercial Online Purchased Edible Pomegranate Seed Oils With New Argentometric Liquid Chromatography Method

The number of online-purchased dietary supplements of diversified origin is exponentially increasing. Pomegranate seed oils (PSOs)—the main dietary source of conjugated linolenic acids (CLnA)—are available as dietary supplements via the Internet. PSO samples (<i>n</i> = 24) were purchased from Internet shops in Poland and China. Chromatographic techniques (gas chromatography coupled with mass spectroscopy [GC-MS] for fatty acids [FAs], liquid chromatography with fluorescence detection for tocopherols, and high-performance liquid chromatography with photodiode array detection for conjugated FAs) were used. The GC-MS method enabled the quantification of 45 FAs, which indicates its superiority to previously used methods. Argentometric liquid chromatography with pre-column mild alkaline hydrolysis for analysis of structural isomers of CLnA does not need preliminary derivatization into volatile compounds, which ensures the absence of artifacts and enables the analysis of the entire conjugated FA profile. PSO differed with tocopherols and FA profile. Some PSOs contained negligible amounts of CLnA, and because of that they did not meet the criteria of valuable, unadulterated nutraceuticals. Obtained results indicate that online purchased PSO shipped from distant places of origin could have been stored in inadequate conditions (temperature, humidity), which caused i.a. deterioration of oxidative quality. Unregulated online availability of dietary supplements of low oxidative quality and nutritive value as well as their intake may be a risk rather than a benefit for consumers. Argentometric liquid chromatography can be a simple, selective, and sensitive tool for screening of dietary supplements containing conjugated FAs and should be considered as an essential way of quality assurance.

多源线上购买的膳食补充剂数量正呈指数级增长。石榴籽油（Pomegranate Seed Oils, PSOs）作为共轭亚麻酸（Conjugated Linolenic Acids, CLnA）的主要膳食来源，可通过互联网作为膳食补充剂流通。本研究共采购24份石榴籽油样品，均购自波兰与中国的线上商铺。本研究采用了多类色谱分析技术：针对脂肪酸（Fatty Acids, FAs）采用气相色谱-质谱联用法（Gas Chromatography-Mass Spectrometry, GC-MS）；针对生育酚采用荧光检测液相色谱法；针对共轭脂肪酸则采用光电二极管阵列检测高效液相色谱法。该GC-MS方法可定量检测45种脂肪酸，其性能优于此前已有的分析方法。针对共轭亚麻酸结构异构体的分析，采用柱前温和碱水解的银量液相色谱法无需预先将待测物衍生为挥发性化合物，可避免人工假阳性产物的生成，并能完整解析共轭脂肪酸的全部组分谱图。不同批次的石榴籽油在生育酚组成与脂肪酸谱上存在显著差异。部分样品中的共轭亚麻酸含量极低，因此不符合优质纯正营养保健品的判定标准。研究结果表明，从远产地运输而来的线上采购石榴籽油，可能处于不适宜的储存条件（温度、湿度）下，进而引发氧化品质劣变等问题。氧化品质与营养价值低下的膳食补充剂在网络上不受监管地流通，且被消费者摄入，这对消费者而言可能带来健康风险而非益处。银量液相色谱法可作为一种简便、专属且灵敏的分析工具，用于筛查含共轭脂肪酸的膳食补充剂，应将其作为保障产品质量的必要手段。