Calendula officinalis L. (pot marigold), a member of the Asteraceae family, is an annual aromatic herb with yellow or golden-orange flowers, native to the Mediterranean climate areas, being also successfully cultivated in temperate regions of the Earth for ornamental and medicinal purposes . The species have been reported to contain a variety of phytochemicals, including carbohydrates, lipids, phenolic compounds, steroids, terpenoids, tocopherols, carotenoids and quinones [2–5] with potential health benefits [1, 6–10].
Besides the usual fatty acids, a few plants are capable to biosynthesize some unusual fatty acids, with special chemical structure. Usually these fatty acids accumulate in storage tissues, while in green organs they are absent or present in very small amounts. The presence of unusual fatty acids is genetically determined and they are highly significant indicators of phylogenetic relationships [11, 12]. The seeds of pot marigold have a significant oil content (around 20%), of which about 60% is the unusual calendic acid (8 t, 10 t, 12c-18:3) [13–16]. Several studies demonstrated that calendic acid is synthesized in Calendula seeds via desaturation of linoleic acid [17–21]. Due to its special structure – with three conjugated double bonds – calendic acid and Calendula seeds oil exhibit interesting chemical and physiological properties.
The seed oils such of Calendula officinalis L., Momordica charantia L. or Aleurites fordii Hemsl., rich in conjugated linolenic acids (CLNAs) have a high rate of oxidation and are used as raw materials in paints and coatings industry, and have applications in the manufacture of cosmetics and some industrial polymers [19, 22–24]. For these reasons, in the last few years, a concentrated research effort in Europe has been directed towards the development of Calendula officinalis L. as an oilseed crop for industrial purposes  and for the engineering of transgenic plants containing the metabolic route for the conjugated fatty acids biosynthesis [26, 27].
The increasing interest for plants producing conjugated fatty acids is also motivated by the recent findings related to their biological effects. It has been shown that CLNAs have an important body fat-lowering effect  and possess anti-carcinogenic properties, exhibiting apoptotic activity against a wide variety of tumor cells, such as the U-937 human leukemic cancer cell line and the colon cancer cells (Caco-2) [24, 29, 30]. Bhaskar et al.  observed that the trans CLNAs exhibited stronger growth inhibition and more DNA fragmentation in human colon cancer cells than corresponding cis CLNA isomers.
To our knowledge, all the studies, excepting two short reports of Ul’chenko et al.  and Pintea et al. , respectively, conducted on marigold seed oils determined the fatty acid contents by analyzing only the total lipid matrix.
Therefore, the aim of the present investigation was to compare the oil content and fatty acid compositions of total lipids (TLs), triacylglycerols (TAGs), polar lipids (PLs) and sterol esters (SEs) in seeds of eleven pot marigold genotypes from six different locations in Europe, grown in the Transylvanian region (Romania). The information obtained is helpful to identify suitable genotypes for use in breeding programs of Calendula officinalis.