Characterization of Haemanthus coccineus extract and its bioactive component: A promising and novel anti-inflammatory approach

Abstract

Haemanthus coccineus (Amaryllidaceae) extracts (HCEs) have been used in traditional African medicine against febrile colds and asthma. The main ingredient of HCE, the non-basic alkaloid narciclasine, was recently reported to induce apoptosis in tumor cell lines [1]. Beyond this anti-cancer action, we hypothesized that HCE and narciclasine could exhibit an anti-inflammatory potential. Dried bulbs of H. coccineus were extracted using 60% (w/w) ethanol. The ethanol was largely removed and the remaining solution was partitioned with ethyl acetate. The organic phase was separated and dried (DER 50:1). The resulting HCE contained 2.2% narciclasine. In vitro, HCE (3 ng/ml to 10 µg/ml) concentration-dependently inhibited the proliferation of lymphocytes and the synthesis of pro-inflammatory cytokines (TNF-α, IL-6, IL-1 β) in murine macrophages without inducing cytotoxicity. Moreover, HCE decreased the TNF-α-induced adhesion of leukocytes to human endothelial cells (ECs) and the surface expression of EC adhesion molecules (ICAM-1, VCAM-1, E-selectin) without affecting EC viability. Extract fractions containing basic alkaloids did not display any activity, whereas the non-basic main alkaloid narciclasine (1 nM to 10µM) clearly reduced adhesion molecule expression. HCE as well as narciclasine attenuated the TNF-α-triggered expression of NF-κB-dependent genes (reporter gene assay) without influencing NF-κB DNA-binding activity (gel shift assay), IκB-α degradation (Western blot), or p65 nuclear translocation (microscopy). In vivo, HCE (450 mg/kg, orally) was found to clearly reduce edema formation and leukocyte infiltration in a dermal ear edema model by croton oil or arachidonic acid (AA). Also in a renal injury model we could demonstrate that HCE (50 µg/animal, i.p.) strongly attenuates leukocyte infiltration and cytokine expression. In conclusion, our study highlights that the use of HCE/narciclasine could represent a novel interesting anti-inflammatory approach.