Carthamus tinctorius L. is the cultivated species of safflower. The word tinctorius essentially means ‘for dyeing’ in English. The flowers of safflower have been used historically as a colorant in food and as dye in the clothing industry. However, the primary purpose today is as an oilseed crop. Safflower oil composition varies widely, but 90% of the oil is made up of oleic and linoleic acids. However, the genes of Carthamus species can be easily manipulated to produce oils with unique fatty acids. As a result, plant breeders are assessing safflower as a potential source of health-promoting oil and as a biodiesel feedstock.
Biodiesel, Bird seed, Carthamus tinctorius L, Colorant, Dye, Flavonoids, Gamma-linoleic acid, Linoleic, Oil, Oleic, Safflower, Tocopherol, Yellow pigment
Carthamus is part of the Compositae or Asteraceae family.
Carthamus tinctorius L. is the cultivated species of safflower.
Flowers of safflower are used as a food colorant and clothing dye and in traditional Chinese medicine.
The oil from safflower is 90% oleic and linoleic acids and is relatively stable to oxidation.
Safflower contains high levels of flavonoids and tocopherols.
Oil composition can be manipulated to create health-promoting oils or biofuel feedstock.
Safflower is an oilseed used in commercial bird foods.
Defatted safflower meal can be used as a cattle feed.
To gain knowledge in the fundamental aspects of safflower production, composition, and uses.
The Food and Agriculture Organization considers safflower (Carthamus tinctorius L.) as a minor oilseed crop since only about 647000 MT, on 783000 Ha, is produced annually. Safflower can be produced on arid and semiarid land, including moderate salinity, and is therefore produced across the world where water is scarce or high salinity water is used for irrigation. Carthamus tinctorius L. is the cultivated species of safflower. The word tinctorius essentially means ‘for dyeing’ in English. The flowers of safflower have been used historically as a colorant in food and as dye in the clothing industry and as a traditional Chinese medicine. However, the primary purpose today is as an oilseed crop. The oil is typically used for cooking and frying, but interest as a feedstock for biodiesel is growing. Safflower oil composition varies widely, but 90% of the oil is made up of oleic and linoleic acids. However, the genes of Carthamus species can be easily manipulated to produce oils with unique fatty acids, which can then be used for specific purposes. In North America, much of the safflower is used as wild bird feed. This article provides the most recent information on safflower, and readers are encouraged to review materials found in the referenced materials, as sources for historical and early agronomic information.
A number of locations have been proposed as the center of origin for safflower. These include Central Asia and the Middle East. Weiss provided an excellent historical perspective of safflower, which dates to 2000 BC in Egypt. The height of safflower production occurred shortly after World War II and has since been replaced with other oilseed crops. Safflower production ranks eighth among oilseeds.
The evolutionary history of safflower has been documented to approximately 1753. Although C. tinctorius L. is the only cultivated species, there were as many as 25 species linked to the genus Carthamus. However, clarification over the last two decades supports the presence of approximately 15 species in the genus Carthamus. Much of the confusion around this genus was due to limited morphological observation such as spiny leaves or cypselas. The advent of molecular biology allowed for the differentiation of Carthamus species.
Carthamus species are grouped into sections based on chromosome pairs. Species with 12 chromosomal pairs include C. tinctorius, C. palaestinus, and C. oxyacantha, while other species contain 10, 11, 22, and 32 chromosomal pairs. C. tinctorius, C. persicus Desf. Ex Willd, C. palaestinus, and C. oxyacantha have 12 chromosomal pairs and can readily cross-pollinate. Only C. tinctorius is commercially produced, while the other three species are wild. However, these species can cross-pollinate resulting in altered seed characteristics. C. tinctorius also can cross with wild species having 10 and 22 chromosomal pairs but not 32. The crossing of C. tinctorius with weedy Carthamus species (e.g., C. lanatus) has been documented. However, the propensity for weediness in the resulting F1 hybrid was less than the parent wild species and no F2 hybrid (i.e., result of crossing of two F1 hybrids) was produced.
A number of factors contribute to the growth characteristics of Carthamus species. However, much of the plant breeding efforts have focused on C. tinctorius L. Therefore, only this commercially relevant species will be presented in the remaining part of this article. Safflower is a thistle-like (Figure 1) plant with yellow, orange, red, or white flowers. Leaves of the mature plants are spiny in nature and thus compared to a thistle, while the seeds resemble a small sunflower (Figure 2). Germination of seeds occurs readily (i.e., 3–4 days) above 60 °F, but growth slows during the rosette (i.e., a circular pattern of growth) stage that lasts up to 3 weeks. The development of a tap root, which can reach lengths of 305 cm, occurs during the rosette stage. This stage of growth is followed by a profuse branching stage of growth. Overall growth behavior is dictated by the plant population, where bush-type plants result from greater spacing, while closer spacing results in an upright plant form. Typical C. tinctorius L. plant heights range from 42 to 113 cm. However, plants can reach heights of 251 cm in Asia. The plant growth behavior also impacts seed yield. Bush-type plants yield greater numbers of flowers as each branch typically has five flowers with up to 50 flower heads per plant. Harvesting of seeds usually begins 30 days after maturing and seed moisture should not exceed 8% moisture. Much of the current breeding focus has been directed at improving oil composition.
Both cultivated safflower and wild species grow in temperate zones under arid and semiarid conditions. Safflower can be grown under diverse conditions, such as drought and salinity, due to the long taproot accessing deep soil moisture. Continued research in area further supports the resilience of this plant. Although safflower can grow under water-restricted environments, Kizil et al. reported that higher amounts of rain significantly increased a number of agronomic characteristics of safflower grown over a 2-year period.
Safflower is composed of approximately 33–45% hull and the remaining fraction being the kernel. Oil content is variable, ranging from 27% to 60% in thick- and thin-hulled cultivars, respectively. The oil is located primarily in the kernel, where greater than 95% of the oil is found. The kernel typically contains approximately 60% oil and 26% protein. However, the protein content of whole seed ranges from 14% to 23%. Fiber content ranges from approximately 11% in thin-hulled cultivars to as high as 34% in thick-walled cultivars.
Most commercial safflower oil consists of 72–78% linoleic acid and represents cultivar and environmental effects on oil composition. Oleic acid is the second most common fatty acid and accounts for 15–20% of the fatty acids in safflower oil. Other fatty acids include palmitic and stearic at levels ranging from 1.5% to 6%. Only a small (< 0.2%) amount of linolenic acid exists in safflower oil. Cultivar (i.e., genotype) is one of the drivers for the diverse oil content and oil fatty acid composition of safflower. Environment also contributes to alteration in oil content and composition. In recent years, modification of genes through molecular approaches has also been used to change oil and fatty acid contents.
Crossing of different C. tinctorius genotypes produces plants with varying oil and fatty acid compositions. Oil contents of 25–33% for eight experimental safflower genotypes have been reported. Linoleic acid represents between 56% and 75% of the fatty acids in the oil. The genotype with the lowest linoleic acid content had both the highest oil content and oleic acid content (i.e., 35% of oil). Attempts to improve oil yields by crossing C. tinctorius genotypes with wild species have had little success, one reason being that the wild species have lower oil contents, that is, 32%, 25%, and 17% for C. tinctorius, C. oxyacantha, and C. lanatus, respectively, compared to greater than 40% for cultivated safflower. However, the two wild species did have slightly higher oleic acid contents compared to C. tinctorius.
Recently, C. tinctorius L. cv. Centennial genotype was genetically altered using a cloned delta-6-desaturase gene from Saprolegnia diclina inserted into the safflower genome by Agrobacterium tumefaciens. This genome manipulation resulted in a safflower with approximately 67% gamma-linolenic acid (GLA), which is not normally present in safflower oil. The health benefit of GLA has been documented and is the primary reason for the development of high-GLA safflower. In contrast, by happenstance, a high-oleic acid safflower was identified in 1957 from seeds grown in India. The seed composition was 77–81% oleic acid and 10–15% linoleic, the opposite of traditional safflower. High-oleic acid safflower is available today due to commercial production of this cultivar.
Although a few reports indicate that temperature can impact linoleic acid content in safflower oil, temperature during growing appears to have less influence on linoleic acid content of safflower compared to other oilseeds. Oleoyl phosphatidylcholine Δ12-desaturase is an enzyme that regulates linoleic acid conversion from oleic acid. Esteban et al. reported that this enzyme was more thermally stable and less oxygen-dependent in safflower compared to the same enzyme in sunflower. The high-(i.e., 72–78%)linoleic acid content observed in safflower grown under high temperatures is contrary to other oilseeds.
Other agronomic practices have significant bearing on agronomic traits. Linoleic acid content was higher in mature seed from the parent seed having later planting dates, while all other agronomic traits such as oil content decreased. Several authors observed that early planting of safflower leads to higher oil content. Seed planting density is another agronomic practice used to enhance yield of many crops. However, safflower tends to branch when sown in wide seed spacing (i.e., less seed density) and thus compensates for the lower plant numbers by producing more seeds per plant compared to greater seed densities. As a result, oil yield per hectare and oil content per seed are not significantly different among plants grown from low- and high-density seeding rates.
Harvesting of safflower usually begins 35–40 days after flowering. These harvesting dates also coincide with maximum oil content. Thus, harvesting date can influence oil yield. The maturity of seed also contributes to the final composition of the seeds. Over the course of 100 days, palmitic and oleic acids increased, while stearic acid decreased. In contrast, linoleic acid reached a maximum at day 75 and then decreased when measured at day 100. Safflower can grow on marginal cropland, including soils of moderate salinity. Under hydroponic conditions, 50 mM sodium chloride was found to inhibit safflower growth and increase the oxygenated essential oils. In general, 7% and 29% reductions in oil content and oil yield, respectively, in safflower subjected to saline stress have been reported. Also, oleic acid tended to increase under saline conditions, while linoleic decreased.
Tocopherols, carotenoids, and phytosterols make up the nonsaponifiable lipid components of safflower oil. Traditional and high-oleic acid safflower oils are composed of approximately 250 μg tocopherol per gram of oil or 50–100 μg tocopherol per gram of seed. However, tocopherol contents as high as 684 and 941 μgg− 1 of oil have been reported for traditional safflower and high-oleic acid safflower oil, respectively. Mean tocopherol concentrations from seven geographic regions in the range of 676–827 μgg− 1 of oil have been reported. No differentiation of safflower oil type was provided, but the lowest and highest tocopherol contents were from East Africa and Southwest Asia geographic locations, respectively.
In traditional safflower, α-tocopherol accounts for 93–98% of the total tocopherols, while β-, γ-, and δ-tocopherols account for the remaining in varying concentrations. α-Tocopherol accounted for 83–98% of the tocopherols in high-oleic acid safflower oil; however, no β analog was found. In addition to tocopherols, 5 and 12 μg of α- and γ-tocotrienols per gram oil, respectively, were reported in cultivated safflower. In contrast to cultivated species, γ-tocopherol contents as high as 36% were reported in oil obtained from wild safflower. A mutant safflower obtained through breeding contained a unique tocopherol profile where γ-tocopherol accounted for 96% of the total tocopherols.
Approximately 29% of the tocopherols are removed during refining, with the greatest removal occurring during the bleaching and deodorization steps of the process. Thus, adjustments to the aforementioned numbers should be considered when refining safflower oil. Roasting of the safflower at temperatures between 140 and 180 °C did not negatively impact tocopherols or tocotrienols.
The safflower carotenoids are present in trace amounts in the oil. Total carotenoid levels of less than 2.5 μgg− 1 oil are common. Lutein and zeaxanthin levels are approximately 0.8 and 1.5 μgg− 1 oil, respectively, as determined by HPLC. However, photometric (445 nm) analysis indicated levels as high as 7 μgg− 1 seed. The underestimations of carotenoids could occur for oils that contain predominantly carotenes. In the case of safflower, trans- and cis-β-carotene levels were only 0.14–0.16 μgml− 1 oil, while α-carotene accounted for less than 0.04 μgml− 1 oil. Therefore, the total carotenoid level close to 2.5 μgg− 1 oil is realistic. Contrary to expectations, the yellow pigments in the flowers of safflower are not carotenoids. Although carotenoid levels as high as 650 μgg− 1 dried flower petals have been reported, hydroxyl safflower yellow A, safflower yellow B, and anhydrosafflor yellow B are the predominant yellow pigments. These pigments are glycosylated flavonoids and thus have high water solubility in contrast to carotenoids.
A significant variation in literature among total, free, and esterified sterol exists. The phytosterol content in safflowers is approximately 2000–4500 μgg− 1 seed. The highest sterol content was obtained in seeds at 24 days after anthesis (i.e., flowering) and stabilized at 2400 μgg− 1 seed at day 47 (i.e., end of maturity). Therefore, the variation in phytosterol data may be due to seed maturity. Phytosterol contents of 1520–5745 μgg− 1 of oil have been reported. In general, the free (~ 48%) sterol form accounts for the majority of the phytosterol content followed by esterified (~ 39%) form. Steryl glycosides and acyl steryl glycosides collectively make up about 13% of the total sterols. Regardless of the sterol form, β-sitosterol accounts for the largest percentage (50–70%) of the phytosterols. Campesterol, Δ7-stigmastenol, Δ5-avenasterol, and stigmasterol each make up 6–12% of the total phytosterol content. Reductions in total sterols due to maturity and refining have been documented; however, the percentage of each phytosterol remains relatively consistent, for example, β-sitosterol accounting for the greatest percentage.
The majority of the phenolic compounds of safflower are located in the flower petals and meal component of the seed. The meals contain 3800–5700 μgg− 1 of phenolic glycosides. Although humans find these compounds bitter, animals appear to be less impacted by the bitterness, and thus, safflower is often used as a protein source in animal rations. Total phenolic contents of water extracts were 40 and 126.0 mg gallic acid equivalence (GAE) per gram flowers and seed, respectively. In contrast, only 26 μg GAE per gram was observed in the oil. Flavonoid contents of safflower water extract obtained from the seed were 62.2 ± 1.9 mg quercetin equivalence per gram, while an extract from dried flowers contained approximately 10 catechin equivalences per gram extract.
Further characterization of the water extract of the seed indicated that the main phenolic compound was (−)-epigallocatechin (109.6 mgg− 1). Other phenolics including 4-hydroxy-benzhydrazide derivative (18.2 mgg− 1), 2-amino-3,4-dimethylbenzoic acid (16.8 mgg− 1), and gallocatechin (17.0 mgg− 1) account for the majority of the remaining phenolic compounds. The phenolic acids trans-ferulic, chlorogenic, p-coumaric, and syringic acids are present at 3.0, 2.4, 0.5, and 0.2 mgg− 1 extract, respectively. Additional flavonoids included naringin, rutin hydrate, quercetin dehydrate, luteolin, and kaempferol at concentrations of 6.0, 3.7, 2.2, 1.6, and 0.8 mgg− 1, respectively. Chlorogenic acid, quercetin-3-galactoside, and gallic acid are present at concentrations of 37–42, 15–16, and 10–12.1 mgg− 1 dried flower petals, respectively. Other phenolic compounds were present at concentrations less than 9 mgg− 1. Although differences in concentrations of phenolics were observed, the general trend in individual phenolics remained consistent regardless of growing location and cultivar.
Although considered a modern use, safflower as a vegetable oil dates to around 260 BC. The use of safflower as a vegetable oil is limited due to the availability of inexpensive commodity oils. However, high-oleic acid safflower has promise as frying oil due to the low level of polyunsaturated fatty acids. Many oxidative stability index evaluations indicate that high-oleic acid safflower oil has comparable oxidative stability to that of high-oleic acid sunflower oil. The oxidative stability of high-oleic acid safflower was further enhanced in a safflower line that contained high γ-tocopherol content. The nonsaponifiable fraction of safflower was found to inhibit frying oil polymerization.
In countries such as Korea, safflower oil is used as condiment oil and is therefore roasted prior to oil extraction. Mild roasting of the safflower seed does not affect fatty acid composition, but increases in tocopherols and oxidative stability have been documented by several researchers. However, excessive heat treatments such as boiling and microwaving decrease tocopherol concentration and oxidative stability. In addition to tocopherol and Maillard browning compounds, formed during roasting, phytosterols and phenolic compounds are thought to stabilize the safflower oil.
Extracts of safflower have been shown to exhibit antioxidant activity and thus could potentially serve as a source of natural antioxidants. Water extracts of safflower seeds showed dose-dependent activity in several radical scavenging assays. The ORAC value of 63 μM Trolox equivalence per gram of seed extract was comparable to that of tomatoes. Radical scavenging properties were also found for extracts of the flower petals. Roasting increased slightly the Trolox equivalent antioxidant capacity (TEAC), while microwaving of the seed significantly increased TEAC compared to the control or raw seed. The list of studies supporting the antioxidant activity of safflower continues to grow. The diverse phenolic composition, yellow pigments, and tocopherol are just a few examples of compounds that likely contribute to the antioxidant activity.
In addition to their antioxidant activity, the pigments of the flowers have been used extensively as a food, cosmetic, and textile dye. Hydroxyl safflower yellow A, safflower yellow B, and anhydrosafflor yellow B are the yellow pigments of safflower, while carthamin is the red color. Unlike the yellow pigments, carthamin has limited water solubility and is therefore used in lipid-based products such as chocolate. The yellow pigments have been used to color cheese and sausage, juice, and candy. The stability of the pigments can be problematic under the presence of light. Carthamin in particular has poor stability when added to aqueous-based food systems. The stability improves in a 75% sucrose–choline solution compared to water. A 90% glucose–choline chloride solution had the greatest stabilizing effect on carthamin. Although degradation occurred, carthamin had greater stability in a xylitol–choline solution than in water under thermal degradation conditions. In contrast to carthamin, the yellow pigments tend to be more stable but tend to degrade slightly under acid conditions. Solution containing lactic acid and ethanol facilitated the rapid degradation of carthamin and to a lesser extent the yellow pigments. Multiple studies have demonstrated the stability issues of safflower pigment. The importance of the food matrix in stabilizing/destabilizing the colorants must be considered if safflower pigments are to be used in foods.
Traditional Chinese medicine has used safflower as a cure for many ailments. However, until relatively recently, evidence supporting the use of safflower as a treatment for many ailments has been lacking. A summary of the pharmacological and medicinal benefits can be found in the literature. However, a few examples include the antiatherogenic effect of N-(p-coumaroyl)serotonin and antiadipogenic effects of N-feruloylserotonin of safflower seed extract. The serotonin derivatives are believed to inhibit the activation of the vascular smooth muscle cells, thereby preventing atherosclerosis. Alcohol extracts of the flowers had matrix metalloproteases-2 (MMP-2) inhibitory activity. MMP-2 are important for many biological functions but if not properly controlled can contribute to the development of diseases such as cancer and atherosclerosis. Therefore, the MMP-2 inhibitory activity of hydroxyl safflower yellow A and safflower yellow B could be important treatments for disease affected by MMP-2.
The use as a clothing dye and a coloring for food has been documented. Safflower as a potential source of health-promoting oil (i.e., high γ-linolenic acid) and as a biodiesel feed stock has attracted attention from commercial entities. Safflower is also a common bird food. Recently, pharmacological and medicinal benefits of safflower have attracted the attention of health researchers. Therefore, the author invites readers to review these source materials.
A significant body of knowledge exists regarding the production and composition of safflower. However, additional production research related to stressed environments such as high salinity and low moisture conditions are needed, specifically improving yield under stress conditions. Furthermore, the use of molecular techniques to alter or enhance composition is needed. The genetic manipulation of safflower to produce high γ-linolenic acid safflower oil represents an opportunity to produce safflower oil with eicosapentaenoic acid and docosahexaenoic acid, that is, long chain omega-3 fatty acids are important for health and are normally found in fish and algae. Safflower is unique among many oilseeds in that temperature during growing and seed filling does not significantly affect unsaturated fatty acid content. Therefore, greater production area could be achieved in contrast to oilseeds that have temperature-dependent regulation of unsaturated fatty acids.
Expanding the understanding of the functional characteristics of safflower seed and flower is needed. Several studies have documented the color stability of flower extracts in various model systems. However, additional investigation is needed in food-based systems. The bitterness associated the meal, while not a deterrent in animal feed, is not well suited for human consumption. Identifying ways to reduce or eliminate the bitterness at a commercial level is needed. Alternatively, methods to extract and purify the bitter compounds could be justified if sufficient bioactives could be isolated. Some of the bitter compounds have biological activity in model systems. Traditional Chinese medicine has used safflower for treatment of a number of aliments; however, the active components are not fully characterized. Although a number of studies have been completed, there is still a need to assess the bioactivity of safflower.
What parts of the safflower can be used for food, feed, biofuel, coloring, and bioactive compounds?
Why is safflower grown worldwide?
What factors influence the growth of safflower?
Why is the taproot of safflower important?
How does growing environment affect safflower seed composition?
Why is safflower unique among oilseeds in terms of fatty acid composition?
What bioactive compounds are present in safflower and what part of the plant can these compounds be found?
What type of safflower oil can be used as frying oil? What makes this oil well suited for frying applications?
Why is safflower a potential source of omega-3 lipid?
Why is the yellow pigment not commonly used in food systems?
How does safflower differ from other oilseeds in terms of production and oil content and fatty acid composition? Cross-reference to oilseed articles.
Identify several countries that produce safflower and compare production practices and oilseed qualities among the produced seeds? Do any countries use wild safflower?
Why is defatted safflower meal used only for livestock feed and not human food? How does this compare to other oilseed meals? Cross-reference to oilseed articles.
Bioactives and Toxins: Bioactives: Antioxidants; Fats: Healthy Fats and Oils; Lipid Chemistry; Food Grains and Well-being: Functional Foods: Overview; Genetics of Grains: Development of Genetically Modified Grains; The Oilseeds: Canola: Overview; Linseed: Overview; Oilseeds: Overview; Soybean: Overview; Sunflower: Overview; Cottonseed: Overview.
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