Kalanchoe fedtschenkoi R. Hamet & H. Perrier, a non-conventional food plant in Brazil: HPLC-DAD-ESI-MS/MS profile and leaf histochemical location of flavonoids

Abstract

Kalanchoe fedtschenkoi (Crassulaceae) is a non-commercial food species in Brazil, whose leaves are used in several aqueous preparations. Their morphology and potential nutraceuticals (e.g., antioxidant phenolics) have been poorly studied. Anatomical features are useful for the correct identification of plants, avoiding their misuse. We describe the anatomy and tissue flavonoid location of K. fedtschenkoi leaves, as well as the phenolic composition and the antioxidant activity of their aqueous extracts. The succulent leaves have a unistratified epidermis with anisocytic or helicocytic stomata, collateral vascular bundles, and phenolic idioblasts throughout the leaf blade. NP-reagent tests suggested the presence of kaempferol derivatives (yellow fluorescence) in the regular epidermis cells, subsidiary cells, and leaf mesophyll. An orange color, assigned to quercetin derivatives, was detected in stomata guard-cells and below the epidermis. The HPLC-DAD-ESI-MS/MS evidenced the presence offlavonoids, mostly kaempferol glycosides (especially sagittatin A), some of them firstly described as constituents of K. fedtschenkoi. The extracts also showed high antioxidant activity. We report, for the first time, the complete anatomical description of K. fedtschenkoi leaves, the tissue location of flavonoids, and the flavonoid composition of the extracts. The high flavonoid content and antioxidant activity of K. fedtschenkoi leaves can be an advantage for their consumption as a food, in addition to being a possible source of nutraceuticals.