Phenylpropanoid metabolism and pharmacology of the blood lily, Scadoxus puniceus, a highly traded South African medicinal plant

Abstract

The current study utilised ultra-high performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometry (UHPLC-MS/MS) to quantify the phenolic compounds in different organs of Scadoxus puniceus (Amaryllidaceae), an important South African medicinal plant. The antioxidant, antimicrobial and acetylcholinesterase (AChE) inhibitory activities of this species were also evaluated. UHPLC-MS/MS revealed a greater profusion of hydroxycinnamic acids (HCAs), accounting for 69.5% of the total phenolic acids as opposed to hydroxybenzoic acids (HBAs). Chlorogenic acid (CGA; 3-caffeoyl-D-quinic acid) was highly abundant (49.6% of HCAs) in the aerial organs suggesting a functional role of the compound against herbivory from the Amaryllis leaf borer which infested many of the stock plants. In addition to CGA, the current study is the first to report the presence of sinapic, gallic and m-hydroxybenzoic acids in the Amaryllidaceae. The accumulation of CGA in the leaves of S. puniceus substantiated the fact that leaf extracts exhibit significantly improved antioxidant activity (DPPH IC50 = 0.07 mg/mL) as compared to the bulb. CGA, a known antifungal agent conferred potent antifungal activity (minimum inhibitory concentration; MIC < 0.10 mg/mL) of leaf extracts against Candida albicans. Furthermore, ethanolic extracts of different organs of S. puniceus revealed AChE inhibitory activity in excess of 90% (IC50 = 0.07 – 0.15 mg/mL), with no significant difference between bulb and leaf extracts.