Secondary Metabolites of Medicinal Plants. Bharat Singh

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2.21 Carthamus Species

      2.21.1 Ethnopharmacological Properties and Phytochemistry

      Carthamus tinctorius L. (Fam. – Asteraceae) is a very good purgative, analgesic, antipyretic, and an antidote to poisoning (Asgarpanah and Kazemivash 2013). It is a useful plant for painful menstrual problems, postpartum hemorrhage, whooping cough and chronic bronchitis, rheumatism, and sciatica (Wang and Li 1985). The flowers of C. tinctorius are an important medicinal material in prescriptions used for cardiovascular, cerebrovascular, and gynecological diseases (Yao et al. 2016). In China, the water extract of C. tinctorius has been developed as an intravenous injection, which is extensively applied to treat cardiovascular diseases clinically (Zhou et al. 2009). Its dye is mainly used as a coloring agent (Shirwaikar et al. 2010).

Carthamus tinctorius flowers are used in formulation of drugs in Chinese medicine and recommended as remedy for treatment of gynecological diseases, heart diseases, and inflammations. C. tinctorius petals were evaluated for the presence of flavonoids, viz (2R)-4′,5-dihydroxyl-6,7-di-O-β-D-glucopyranosyl flavanone and methyl-3-(4-O-β-D-glucopyranosylphenyl) propionate, and were isolated along with four known compounds: (2S)-4′,5-dihydroxyl-6,7-di-O-β-D-glucopyranosyl flavanone, 6-hydroxykaempferol-3,6-di-O-β-D-glucopyranoside, 4-O-β-D-glucosyl-trans-p-coumaric acid, and 4-O-β-D-glucosyl-cis-p-coumaric acid (Li et al. 2002). The known flavonoids, luteolin, cinaroside, 5-O-methylluteolin, azaleatin (3,7,3′,4′-tetrahydroxy-5-methoxyflavone), and the new natural products 3,7,3′,4′-tetrahydroxy-5-methoxyflavone, 7-O-β-D-glucopyranoside, hydroxysafflor yellow A, 6-hydroxykaempferol 3,6-di-O-β-glucoside-7-O-β-glucuronide, 6-hydroxykaempferol 3,6,7-tri-O-β-glucoside, 6-hydroxykaempferol 3-O-β-rutinoside-6-O-β-glucoside, 6-hydroxykaempferol 3,6-di-O-β-glucoside, 6-hydroxyapigenin 6-O-glucoside-7-O-glucuronide, anhydrosafflor yellow B, kaempferol 3-O-β-rutinoside, and syringin were isolated and characterized from C. tinctorius flowers (Zhou et al. 2008; Fan et al. 2009; Kurkin and Kharisova 2014). Carthamin, safflor yellows A and B, safflomins A and C, isocarthamin, isocarthamidin, hydroxysafflor yellow A, and tinctormine have been characterized from these flowers, as well as several new phenolic compounds. The dried flowers of C. tinctorius, cultivated in Sichuan, China, were extracted with 95% ethanol, and the extract was partitioned between H₂O and organic solvents. The water fraction was subjected to chromatographic studies, and several compounds were isolated, viz 6-hydroxykaempferol 3-O-glucoside, 6-hydroxykaempferol 7-O-glucoside, kaempferol 3-O-rutinoside, quercetin 3-O-glucoside (Li and Che 1998; Fan et al. 2011). Quinochalcone C-glycosides are regarded as characteristic components that have only been isolated from the florets of C. tinctorius. Recently, quinochalcone C-glycosides were found to have multiple pharmacological activities, which has attracted the attention of many researchers to explore these compounds (Yue et al. 2013). Two new acetylenic glucosides, 4′,6′-acetonide-8Z-decaene-4,6-diyne-1-O-β-D-glucopyranoside named carthamoside A and 4,6-decadiyne-1-O-β-D-glucopyranoside named carthamoside A, along with one known acetylenic glucoside, 8Z-decaene-4,6-diyne-1-O-β-D-glucopyranoside, have been isolated from the air-dried flower of C. tinctorius; these structures have been identified via spectroscopic methods (Zhou et al. 2006).

      Several flavonoids were isolated and identified as 6-hydroxyquercetin 3,6,7-tri-O-β-D-glucoside, 6-hydroxykaempferol-3,6-di-O-β-D-glucoside-7-O-β-D-glucuronide, 6-hydroxykaempferol-3,6,7-tri-O-β-D-glucoside, 6-hydroxykaempferol-3-O-β-D-glucoside, 6-hydroxykaempferol-3-O-β-D-rutinoside, 6-hydroxykaempferol-6,7-di-O-β-D-glucoside, 6-hydroxyapigenin-6-O-β-D-glucoside-7-O-β-D-glucuronide, 6-hydroxykaempferol-3,6-di-O-β-D-glucoside, 6-hydroxykaempferol-3-O-β-rutinoside-6-O-β-D-glucoside, and (2S)-4′,5-dihydroxyl-6,7-di-O-β-D-glucopyranosyl flavanone from C. tinctorius (Fan et al. 2011). Two quinochalcone C-glycosides, carthorquinosides A and B, were isolated from the florets of C. tinctorius (Yue et al. 2016).

      Carthamus tinctorius was evaluated for antioxidant activities against several models in vitro. The antioxidant activity was determined on the basis of the capacity to scavenge DPPH radical and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical and reduced Fe³⁺ of different polar fractions. Five major components were isolated and identified from water extract as 6-hydroxykaempferol 3,6,7-tri-O-β-D-glucoside, 6-hydroxykaempferol 3-O-β-rutinoside-6-O-β-D-glucoside, 6-hydroxykaempferol 3-O-β-D-glucoside, hydroxysafflor yellow A, and anhydrosafflor yellow B. By evaluating and comparing the antioxidative effects of different fractions and obtained compounds, the results showed that water extract displayed significantly high antioxidative activities and 6-hydroxykaempferol glycosides and quinochalcone C-glycosides were found as main contribution for their antioxidant property (Yue et al. 2013, 2014).