Castilleja tenuiflora Benth. (Scrophulariaceae, “cancer herb”) is a wild plant widely
recommended in Mexican folk medicine to treat tumors. Root and shoot cultures of this species were
established for the production of secondary metabolites with cytotoxic and antioxidant activities. Root
cultures were initiated from root tips induced in leaf explants from wild-grown plants using MS medium and
10 μM α-naphthalene acetic acid. Shoots spontaneously formed in 30-35 days and were excised. They
presented continuous multiplication and elongation during subsequent subculture in free-hormone liquid
medium. Antioxidant activity was measured using three in vitro models [scavenging of free radicals with
1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)
diammonium salt (ABTS), and the transition metal reduction in the phosphomolybdenum assay], and the
strongest activity (p<0.05) was found in methanol extracts from shoot cultures. The highest contents of the
phenolic compounds, flavonoid and iridoids, were also found in shoot cultures (p<0.05). Total phenolic
compound levels correlated significantly with the antioxidant activity (p<0.05). Bioautography within TLC
using DPPH as a detection reagent indicated that quercetin 3-β-D-glucoside is one of the predominant
contributors to the free radical scavenging of C. tenuiflora organ cultures. Aucubin, an iridoid with cytotoxic
activity, was also found in the in vitro cultures. C. tenuiflora organ cultures are alternative sources for
iridoids and natural antioxidants such as flavonoids and other phenolic compounds.
Keywords: Castilleja tenuiflora, Scrophulariaceae, oxidative stress, secondary metabolites, iridoid,
biotechnology, micropropagation, cell suspension culture, callus, explant, organogenesis, root culture, shoot
culture, chemical composition.