Phytochemical, morpho-anatomical and histochemical characterization of Cyclolepis genistoides (asteraceae)

Cyclolepis genistoides (Asteraceae), commonly known as "palo azul", is South American a medicinal shrub traditionally used as diuretic, analgesic, antispasmodic, antiarthritic, antirheumatic, and kidney and liver disorders. Despite its ethnopharmacological relevance, the chemical composition of traditional aqueous preparations and the localization of bioactive compounds in plant tissues remain poorly understood. Aerial parts of wild C. genistoides were collected in Amaicha del Valle, Tucumán, Argentina. Infusion (INF), decoction (DEC), macerate (MAC), and hydroalcoholic extract (HE) were prepared from dried leaves and stems. Lipophilic fractions were separated using dichloromethane and analyzed by GC-MS and HPLC. Total phenolics and flavonoids were quantified colorimetrically, and antioxidant activity was assessed using DPPH• and ABTS•+ assays. Anatomical and histochemical analyses were conducted using light, fluorescence, and scanning electron microscopy. The sesquiterpene lactone [(1R,3S,5R,6S,7S,10R)-3β,10α-dihydroxyguaia-4(15),11(13)-dien-6α,12-olide] and the coumarins fraxidin and scopoletin were identified for the first time in "palo azul". Phenolic profiles of all extracts (DEC, INF, MAC and HE) were dominated by chlorogenic and caffeoyl-feruoylquinic acids. Among the extracts, DEC exhibited the lowest, while HE showed the highest antioxidant activity. Anatomical analyses revealed amphistomatic leaves, capitate trichomes, aquiferous parenchyma, chlorenchymatous outer cortex, accessory bundles, and sclerified pith. Histochemical tests revealed that parenchyma cells and glandular trichomes are key sites of metabolite synthesis and storage. These findings demonstrate that the pharmacological potential of C. genistoides aqueous extracts arises from synergistic interaction among bioactive metabolites localized in its vegetative tissues.